FORMULATION OF PERSONAL CARE PRODUCTS WITH BIO- …

FORMULATION OF PERSONAL CARE PRODUCTS WITH BIO-

SURFACTANTS

A thesis submitted to The University of Manchester

for the degree of Doctor of Philosophyin the Faculty of Science and Engineering

2021

Chi Zhang

School of EngineeringDepartment of Chemical Engineering amp Analytical Science

1

Table of Contents

Chapter 1 Introduction 17

11 Research System 17

12 Research Motivation 18

13 State-of-the-Art 19

14 Research Objectives and Aims 30

15 Overview of Thesis 30

16 Nomenclature 31

Chapter 2 Literature Review 32

21 Surfactants 32

211 Structure of Surfactants 33

212 Classification of Surfactants 33

213 Surfactant Behaviour in Water Solution 39

22 Bio-surfactants 44

221 Classification of Biosurfactants (BSs) 45

222 The Production and Extraction of Biosurfactants (BSs) 46

223 Characterization of Biosurfactants (BSs) 48

224 Application of Biosurfactants (BSs) in Various Fields 49

225 Potential Cosmetic-applicable Biosurfactants (BSs) 51

23 Emulsion 65

231 Overview of Emulsion 66

232 Emulsion Formation 66

233 Mechanisms of Emulsion Instability 73

24 Rheology 75

241 Rheology of Emulsions 75

242 Rheometry and Rheometers 77

Chapter 3 Materials and Methodology 81

31 Sophorolipids (SLs) Production 81

311 Producing Microorganisms 81

312 Chemicals 81

313 Production Strategies 81

32 Mannosylerythritol Lipids (MELs) Production 84

2


322 Chemicals 84


33 Preliminary Trials on Cream Formulation 86

331 First Trial for Formulation of Cream without Sodium Lauryl Ether

Sulfate (SLES) Using a Homogenizer 86

332 Second Trial for Formulation of Cream with Sodium Lauryl Ether

Sulfate (SLES) Using an overhead stirrer 87

34 Modified and Standard Experimental Procedure for Cream Formulation

90

341 Chemicals 90

342 Recipes 90

343 Apparatus and Configurations 95

344 Preparation Procedure for Standard Formulation 96

35 Modification of Preparation Process 97

351 Formulation of Model Creams 98

352 Preparation Procedure with Different Mixing Time During Heating

Procedure 98

353 Preparation Procedure with Different Mixing Speed During Heating

Procedure 99

354 Preparation Procedure with Different Cooling Procedure 100

36 Characterisation Methods 100

361 Rheology 101

362 Differential Scanning Calorimetry (DSC) 121

363 Droplet Size Distribution Analysis 126

364 Microscopy 132

365 Surface and Interfacial Tension Measurement 132

366 Mass Spectrometry (MS) and Tandem Mass Spectrometry (MS-

MS) 136

Chapter 4 Preliminary Characterisation of E45 Cream 139

41 Rheological Characterisation of E45 cream 139

411 Preliminary Testing Conditioning Step Determination 139

412 Rheological Characterisation on E45 Cream 146

42 Droplet Size Distribution (DSD) Analysis 152

421 Experimental Procedure 152

422 Results and Conclusions 154

3

43 Differential Scanning Calorimetry (DSC) Analysis 155



44 Summary of Chapter 4 156

Chapter 5 Variation of Mimic Creams Prepared with Different Emulsifying

System 158

51 Explorer Formulation of Mimic Creams 158

511 First Trial of Cream Formulation without Sodium Lauryl Ether


512 Second Trial of Cream Formulation with Sodium Lauryl Ether

Sulfate (SLES) Using an Overhead Stirrer 159

52 Formulation_Ⅰ of Cream Formulation Using a Simplified Configuration

161

521 Appearance of Mimic Creams in Formulation_Ⅰ 161

522 Rheological Characterisation of Mimic Creams in Formulation_Ⅰ

163

523 Droplet Size Distribution Analysis of mimic creams in

Formulation_Ⅰ 180

524 Thermodynamic Properties of Mimic Creams in Formulation_Ⅰ 182

53 Complementary Rheology Study of Creams Formulated in

Formulation_Ⅱ 184


Chapter 6 Variation of Creams Prepared with Different Processes 188

61 Effect of Mixing Time on Cream Formulation During Heating Procedure

188

62 Effect of Mixing Speed on Cream Formulation During Heating Procedure

192

63 Effect of Cooling Procedure on Cream Formulation 193


Chapter 7 Production of Bio-surfactants 199

71 Sophorolipids (SLs) 199

711 Structural Analysis of Sophorolipids (SLs) 201

712 Surface Tension Analysis of Sophorolipids (SLs) 202

72 Mannosylerythritol Lipids (MELs) 204

721 Structural Analysis of MELs 204

73 Thermodynamic Properties of Sophorolipids and MELs 207

4


Chapter 8 Production of bio-creams using Continuous Configuration

in Formulation_Ⅲ 209

81 Reformulation of Mimic Creams Using Continuous Configuration 209

82 Creams Formulated with Bio-surfactants in Mixed Paraffin OilsWater

System 210

821 Appearance of Creams 211

822 Rheological Properties of Creams 211

823 Thermodynamic Properties of Creams 223

83 Creams Formulated in Vegetable OilsWater System 225





Chapter 9 Conclusion and Future Work 245

References 249

5

List of Figures

Figure 21 Dependence of surface tension on the concentration of various solutes 32

Figure 22 Schematic diagram of surfactant molecule 33

Figure 23 schematic diagram of different types of surfactant molecules alignment at

water surface 39

Figure 24 Dependence of structure and phase formation on the surfactant

concentration and temperature adapted from Guo et al 2018 42

Figure 25 General structure of sophorolipids (SLs) 55

Figure 26 General structure of mannosylerythritol lipids (MELs) 61

Figure 27 Instability phenomena of emulsions 74

Figure 31 Schematic diagram of simplified configuration and photo of overhead stirrer

89

Figure 32 Schematic diagram of continuous configuration and corresponding container

parameters that applied in Formulation_Ⅲ 96

Figure 33 Flow behaviour of fluids plotted in shear stress-shear rate (left) and viscosity-

shear rate (right) diagram according to Mezger 2020 103

Figure 34 Schematic diagram of steady state shear and generated shear profile

according to Mezger 2020 104

Figure 35 Qualitative S-shape rheological curve for typical shear thinning fluids and

corresponding model fitting range according to Tatar et al 2017 105

Figure 36 Typical hysteresis loop of shear stress-shear rate behaviour for thixotropic

and rheopectic material according to Maazouz 2020 108

Figure 37 Schematic diagram of spring represents elastic behaviour (left) and dashpot

represent for viscous behaviour (right) 108

Figure 38 Creep and recovery test (a) and expected response of different materials

response of linearly elastic material (b) response of viscous liquid (c) 109

Figure 39 Schematic diagram of Maxwell model 110

Figure 310 Creep and recovery test (a) and expected response of Maxwell model (d) 110

Figure 311 Schematic diagram of Kelvin-Voigt model 111

Figure 312 Creep and recovery test (a) and expected response of Voigt model (b) 112

Figure 313 Typical creep and recovery response (a) for Burgers model accompanied

with its schematic diagram (b) 112

Figure 314 Response of viscous material and elastic material to creep test expressed

with creep compliance with time in log-log plot 113

Figure 315 Two-plate model for oscillatory shear test and the applied oscillatory shear

profile 114

Figure 316 Typical frequency response of Maxwell model for a viscoelastic liquid (a) and

Voigt model for a viscoelastic solid (b) 117

Figure 317 Physical model of rheological measuring system 118

Figure 318 Schematic diagram of cone and plate geometry 119

Figure 319 Schematic diagram of power compensation DSC adapted from Danley 2002

122

Figure 320 Schematic diagram of heat flux DSC 123

Figure 321 Schematic diagram of Tzero measurement model for DSC 124

6

Figure 322 Schematic diagram of Laser diffraction when encountering different size of

particles 126

Figure 323 Diffraction patterns and the corresponding radial intensity for two spherical

particles 1 (a) and 2 (b) in different sizes 127

Figure 324 Schematic diagram of laser diffraction particle size analyser 127

Figure 325 Droplet size distribution of a sample and the corresponding illustration of

size classes 128

Figure 326 Illustration of instrument Mastersizer 3000 connecting to the wet dispersion

unit 130

Figure 327 Schematic diagram of force that applied to increase the surface area and

the surface tension is proportional to this measured force 133

Figure 328 Physical model of tensiometer 134

Figure 329 Schematic illustration of Du Nouumly ring method (left) and its cross-section

view (right) 135

Figure 330 Schematic diagram of the theory of a mass spectrometry 137

Figure 331 Schematic diagram of the theory of mass spectrometry 138

Figure 41 Exploratory flow characterisation of E45 cream for pre shear stress

determination where viscosity varied as a function of shear stress 143

Figure 42 Oscillatory amplitude sweep of E45 cream for determination of oscillatory

stress within linear viscoelastic range 144

Figure 43 Oscillatory time sweep of E45 cream for determination of equilibrium time

145

Figure 44 Steady state shear test on E45 cream where viscosity varied as a function of

shear stress ranging from 10 Pa to 300 Pa 149

Figure 45 Shear ramp test on E45 cream for determination of hysteresis loop where

shear stress ramped up and down as a function of shear rate 151

Figure 46 Oscillatory frequency sweep on E45 cream where Grsquo and Grsquorsquo varied as

function of angular frequency from 001 rad s-1 to 1000 rad s-1 at controlled oscillatory

stress of 4 Pa 152

Figure 47 Comparison of the droplet size distribution curves between sample A of pre-

treated E45 cream and sample B of pre-treated E45 cream with additional 2wt of SLES

154

Figure 48 DSC thermogram of E45 cream (screen shot directly from the software) 156

Figure 51 Appearance of mimic cream prepared in the first trial using CA as the sole

surfactant and a homogenizer for mixing 158

Figure 52 Appearance of mimic cream prepared in the second trial using CA and SLES as

surfactants and a stirrer with pitched blade turbine for mixing 159

Figure 53 Comparison of representative flow behaviour between E45 cream and mimic

cream that emulsified by SLES and cetyl alcohol where viscosity varied as a function of


Figure 54 Appearances of mimic creams prepared in Formulation_Ⅰ 162

Figure 55 Flow profiles of 12 mimic creams prepared in the Formulation_Ⅰ using

simplified configuration where viscosity varied as a function of shear stress from 5 Pa to

300 Pa 164

7

Figure 56 Respective comparison of average of limit viscosity and corresponding yield

stress among mimic creams formulated with varied emulsifying system 166

Figure 57 Oscillatory strain sweep on mimic creams formulated with 6 wt CA and 2

wt GM with varied concentration of SLES where G and G varied as function

of strain ranging from 001 to 100 169

Figure 58 Oscillatory frequency sweep on mimic creams formulated with 6 wt CA and

2 wt GM with varied concentration of SLES where G G and |η| varied as a function

of frequency ranging from 001 Hz to 100 Hz 173

Figure 59 Comparison between steady shear viscosity and complex viscosity

respectively varied as a function of shear rate and angular frequency for cream

containing 2 wt SLES 6 wt CA and 2 wt GM 174

Figure 510 Comparison of storage and loss moduli among creams containing 6 wt CA

and 2 wt GM with varied concentration of SLES where storage and loss moduli varied

as a function of frequency ranging from 001 Hz to 1000 Hz 175

Figure 511 Comparison of dissipation factor among creams containing 6 wt CA and 2

wt GM with varied concentration of SLES where dissipation factor varied as a function


Figure 512 Comparison of the compliance (J) response among creams containing 6 wt

CA and 2 wt GM with varied concentration of SLES where compliance varied as a

function of time Curve illustrated with mean values and standard deviations were

00002 1Pa for 2 wt SLES involved 00002 1Pa for 4 wt SLES involved 00003 1Pa

for 6 wt SLES involved 178

Figure 513 Typical plot of compliance varied as a function of time in a creep-recovery

test for a viscoelastic material 179

Figure 514 Mechanical model for interpretation of creep-recovery result 179

Figure 515 Comparison of droplet size distribution among creams containing 6 wt CA

2 wt GM with varied concentrations SLES where volume density varied as a function

of diameter Mean values are presented in curve for each cream 180

Figure 516 Microscopic observation of mimic creams containing 6 wt CA 2 wt GM

with varied concentrations of SLES 181

Figure 517 DSC thermogram of cetyl alcohol and glycerol monostearate 182

Figure 518 DSC thermogram of light liquid paraffin and white soft paraffin 183

Figure 519 DSC thermogram of sodium lauryl ether sulfate (screen short directly from

software) 183

Figure 520 Comparison of thermal behaviour among creams containing 6 wt CA 2

wt GM with varied concentrations SLES where heat flow varied as a function of

temperature ranging from 25 degC to 90 degC 184

Figure 61 Effect of varied mixing time during heating procedure on droplet size

distribution of creams containing 6 wt CA and 2 wt GM with varied concentrations of

SLES at controlled mixing speed of 500 rpm 189




8


and 2 wt GM with 2 wt SLES respectively being mixed at 500 rpm 700 rpm and 900

rpm for 3 minutes Data presented as the mean value 192

Figure 64 Comparison of D [3 2] values among creams containing 6 wt CA and 2 wt

GM with varied concentrations of SLES respectively being mixed at 500 rpm 700 rpm

and 900 rpm for 3 minutes Data is presented with the standard deviation as error bar

193

Figure 65 Comparison of different cooling procedures on cream containing 6 wt CA

and 2 wt GM with 4 wt SLES where viscosity varied as a function of shear stress

ranging from 1 Pa to 300 Pa 195

Figure 66 Comparison of varied stirring speed during cooling procedure for 10 min on

cream containing 6 wt CA and 2 wt GM with 4 wt SLES where storage modulus

varied as a function of frequency ranging from 01 Hz to 100 Hz 197

Figure 67 Comparison of varied stirring duration during cooling procedure at controlled

stirring speed of 200 rpm on cream containing 6 wt CA and 2 wt GM with 4 wt

SLES where storage modulus varied as a function of frequency ranging from 01 Hz to

100 Hz 197

Figure 71 Phase separation of media broth of sophorolipids production 199

Figure 72 Appearance of extracted sophorolipids (a) right after rotary evaporation and

(b) after 24h dried in fume cupboard 200

Figure 73 Result of HPLC measurement of sophorolipids 201

Figure 74 Representative mass spectrum of sophorolipids obtained from mass

spectrometry 202

Figure 75 Surface activity of SLs in water solution where surface tension varied as a

function of the concentration of sophorolipids 203

Figure 76 Appearance of MELs products from (a) batch fermentation and (b) fed-batch

fermentation 204

Figure 77 Results of mass spectrometry of mannosylerythritol lipids 205

Figure 78 Representative mass spectrum of mannosylerythritol lipids with mz ranging

from 600 to 750 205

Figure 79 DSC thermogram of sophorolipids where heat flow varied as function of

temperature ranging from -20 degC to 90 degC 207

Figure 710 DSC thermogram of mannosylerythritol lipids where heat flow varied as

function of temperature ranging from -20 degC to 90 degC 207

Figure 81 Comparison of flow profile among creams formulated in Formulation_Ⅰ

using simplified configurations and that in Formulation_Ⅲ using the continuous one 210

Figure 82 Appearance of bio-creams formulated with 6 wt CA and 2 wt GM

respectively incorporated with varied concentrations of SLs and MELs in mixed paraffin

oils-water system 211

Figure 83 Comparison of flow behaviour among creams containing 6 wt CA and 2wt

GM with varied concentrations of SLs in mixed paraffin oils-water system where

viscosity varied as a function of shear stress ranging from 1 Pa to 300 Pa 213

9


GM with varied concentrations of MELs in mixed paraffin oils-water system where


Figure 85 Oscillatory strain sweep on bio-creams formulated with 6 wt CA and 2 wt

GM with varied concentration of SLs where G and G varied as function of strain

ranging from 001 to 10 216

Figure 86 Oscillatory frequency sweep on bio-creams containing 6 wt CA and 2 wt

GM with varied concentration of SLs where G G and |ƞ|varied as function of

frequency ranging from 001 Hz to 100 Hz 218

Figure 87 Specific oscillatory frequency range of oscillatory frequency sweep test for

SLs-involved cream including the range between 001 and 01 (left) and that between 10

and 100 (right) showing crossover of G and G 219

Figure 88 Comparison of G and G as function of frequency ranging from 001 Hz to 10

Hz among bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of

SLs in mixed paraffins-water system 221



MELs in mixed paraffins-water system 221

Figure 810 Comparison of compliance as a function of time among bio-creams

containing 6 wt CA and 2 wt GM with varied concentrations of SLs in mixed paraffins-

water system 222


containing 6 wt CA and 2 wt GM with varied concentrations of MELs in mixed

paraffins-water system 223

Figure 812 DSC thermograms of bio-creams formulated with varied concentrations of




Figure 814 Appearance of mimic creams formulated involving SLES respectively with

coconut oil and vegetable shortening in water containing surfactant system of 6 wt

cetyl alcohol and 2 wt glycerol monostearate with varied concentrations of sodium

lauryl ether sulfate 225

Figure 815 Appearance of bio-creams formulated involving SLs and MELs respectively

with coconut oil in water containing surfactant system of 6 wt cetyl alcohol and 2 wt

glycerol monostearate with varied concentrations of sodium lauryl ether sulfate 226


with vegetable shortening in water 227

Figure 817 Comparison of flow behaviour among mimic creams containing 6 wt CA

and 2 wt GM with varied concentrations of SLES in coconut oil-water system where

viscosity varied as a function of shear stress ranging from 1 to 300 Pa 229


and 2 wt GM with varied concentrations of SLES in vegetable shortening-water system

where viscosity varied as a function of shear stress ranging from 1 to 300 Pa 229

10

Figure 819 Comparison of flow behaviour among bio-creams containing 6 wt CA and 2

wt GM with varied concentrations of SLs in coconut oil-water system where viscosity

varied as a function of shear stress ranging from 1 to 300 Pa 230


wt GM with varied concentrations of SLs in vegetable shortening-water system where



wt GM with varied concentrations of MELs in coconut oil-water system where



wt GM with varied concentrations of MELs in vegetable shortening-water system


Figure 823 Oscillatory strain sweep on mimic creams containing 6 wt CA and 2 wt

GM with 6 wt SLES in coconut oil-water system where Gand G varied as function of

strain ranging from 001 to 100 234

Figure 824 Oscillatory strain sweep on bio-creams containing 6 wt CA and 2 wt GM

with 6 wt MELs in coconut oil-water system where G and G varied as function of


Figure 825 Oscillatory frequency sweep on mimic creams containing 6 wt CA and 2

wt GM with varied concentrations of SLES in coconut oil-water system where G G

and |ƞ|varied as function of frequency ranging from 001 to 100 Hz 235


wt GM with varied concentrations of SLES in vegetable shortening-water system

where G G and |ƞ|varied as function of frequency ranging from 001 to 100 Hz 236


GM with varied concentrations of SLs in coconut oil-water system where G G and

|ƞ|varied as function of frequency ranging from 001 to 100 Hz 236


GM with varied concentrations of SLs in vegetable shortening-water system where G

G and |ƞ|varied as function of frequency ranging from 001 to 100 Hz 237


GM with varied concentrations of MELs in coconut oil-water system where G G and



GM with varied concentrations of MELs in vegetable shortening-water system where G


Figure 831 Comparison of compliance as a function of time among mimic creams

containing 6 wt CA and 2 wt GM with varied concentrations of SLES in vegetable

shortening-water system 240


containing 6 wt CA and 2 wt GM with varied concentrations of MELs in coconut oil-

water system 240


containing 6 wt CA and 2 wt GM with varied concentrations of SLs in coconut oil-

water system 241

11

Figure 834 DSC thermograms of mimic creams containing 6 wt CA and 2 wt GM with

varied concentrations of SLES in vegetable shortening-water system 242

Figure 835 DSC thermograms of bio-creams containing 6 wt CA and 2 wt GM with

varied concentrations of MELs in vegetable shortening-water system 242


varied concentrations of SLs in coconut oil -water system 243

12

List of Tables

Table 11 Classification of ingredients formulated in E45 cream based on function 18

Table 21 Examples of cationic surfactants and corresponding chemical structures 34

Table 22 Examples of anionic surfactants and corresponding chemical structures 35

Table 23 Example of non-ionic surfactants and corresponding chemical structures 37

Table 24 Classification of bio-surfactants adapted from Shoeb et al 2013 45

Table 25 Typical shear rate ranges of emulsions and creams during different industrial

applications adapted from Mezger 2020 76

Table 26 Theoretical values of shear rate related to different processes of cream

application adapted from Langenbucher and Lange 1970 76

Table 31 Default settings for HPLC measurement for analysing SLs concentration

(Dolman et al 2017) 84

Table 32 Formulation of first trial cream with cetyl alcohol as sole emulsifying agent 86

Table 33 Formulation of second trial cream with cetyl alcohol and SLES as mixed

emulsifying system 88

Table 34 Classification of ingredients in the cream formulation 90

Table 35 Formulation_Ⅰ of mimic creams prepared with varied proportion of

surfactant system 91

Table 36 Formulation_Ⅱ of mimic creams prepared with varied concentrations of fatty

alcohols 92

Table 37 Formulation_Ⅲ of mimic creams and bio creams with optimized surfactant

system 94

Table 38 Ingredients for cream preparation in Formulation_Ⅰand Formulation_Ⅱ 96

Table 39 Formulation of model creams used for studying the effect of different

manufacturing strategies on cream performance 98

Table 310 Parameters of different mixing durations applied for study the effect of

different mixing procedure on product performance 99

Table 311 Specification of different mixing speeds during heating procedure applied for

study the effect of different mixing procedure on product performance modified from

Boxall et al 2010 100

Table 312 Specification of different cooling procedures applied for study the effect of

different cooling procedures on product performance adapted from Roslashnholt et al 2014

100

Table 313 Classification of Non-newtonian fluids according to Mezger 2020 103

Table 314 Non-Newtonian models with constitutive equations according to Mezger

2020 105

Table 315 Parameters for steady state shear test (SSS) 120

Table 316 Parameters for oscillatory strain sweep test (OSS) 120

Table 317 Parameters for oscillatory frequency sweep test (OFS) 120

Table 318 Parameters for creep and recovery test 121

Table 319 Details for SOP applied in droplet size analysis for mimic cream 132

13

Table 41 Parameters of pre-shear stress determination for E45 cream characterisation

140

Table 42 Parameters for preliminary linear viscoelastic range (LVER) determination for

E45 cream characterisation 141

Table 43 Parameters for equilibrium time determination for E45 cream characterisation

142

Table 44 Parameters for steady state shear test on E45 cream 146

Table 45 Parameters for continuous shear stress ramp test on E45 cream 147

Table 46 Parameters for new linear viscoelastic range (LVER) determination for E45

cream characterisation 147

Table 47 Parameters for oscillatory frequency sweep on E45 cream 148

Table 48 Details of SOP applied in droplet size analysis for E45 Cream 153

Table 51 Results of steady state shear measurement for E45 and mimic cream

containing SLES and CA 161

Table 52 Key parameters derived from viscosity profiles of creams containing 6 wt CA

and 2 wt GM with varied concentrations of SLES 166

Table 53 Key parameters derived from viscosity profiles of cream containing 2 wt SLES

and 2 wt GM with varied concentrations of CA 185



Table 61 Sauter mean diameter D[3 2] in cream containing 6 wt CA and 2 wt GM

with varied concentrations of SLES being mixed at 500 rpm at ifferent mixing time The

value is presented as mean value plusmn standard deviation 189

Table 62 Sauter mean diameter D [3 2] in cream containing 6 wt CA and 2 wt GM

with varied concentrations of SLES respectively being mixed at 700rpm and 900rpm at

different mixing time The value is presented as mean value plusmn standard deviation 191

Table 63 Parameters for cooling process where mixing speed and mixing time are

specified 194

Table 64 Key parameters derived from viscosity profile of cream containing 4 wt SLES

with 6 wt CA and 2 wt GM formulated with different cooling procedure 195

Table 71 Prediction of MELs structure and corresponding possible fatty acid chains 206

14

Abstract

Personal care products are necessities in peoplersquos daily life especially cosmetic

creams and lotions Cosmetic creams are semi-solid emulsions most of which are

normally at a thermodynamically metastable state thus surfactants play a key role

in the formulation Most industrially applied surfactants are chemically synthesized

which are poorly biodegradable and biocompatible With the increase in concern

for environment protection considerable attention has been given to biosurfactants

due to their environmentally friendly merits and higher surface activity

This project aims to study the preparation of cosmetic cream formulated with

biosurfactants compared to a system of containing cetyl alcohol (CA) glycerol

monostearate (GM) and sodium lauryl ether sulfate (SLES) with paraffin in water

Instead of applying the petroleum-based surfactants the cream will be

reformulated with microbial-derived surfactants eg sophorolipids (SLs) and

mannosylerythritol lipids (MELs) Key parameters for the performance of the cream

are analysed to allow understanding of the production process and the effect of

replacing the surfactant Droplet size analysis was performed using a Mastersizer

3000 The d32 of the distributions were used to determine the dependencies of the

surfactant concentrations the rotor speed and the mixing time used to

manufacture the cream Rheological properties of the cream were also examined

eg shear stress sweep and linked to the droplet size distributions As a result

structural mixture of SLs mainly consisting of diacylated acidic SLs of C181

diacylated acidic SLs with C201 and diacylated lactonic SLs with C181 that

extracted from c bombicola cultivation consuming glucose and rapeseed oil as

substrates was successfully incorporated with fatty alcohols for cream formulation

in replacement of anionic surfactant SLES In this study bio cream with 6 wt SLs

exhibited smooth texture with sufficient stiffness reflecting as an average

maximum viscosity of approximate (2plusmn07)times105 Pamiddots And a primary creep was

obtained from creep test indicating a solid behaviour of the system Also higher

concentration of SLs formulated in cream system led to better result with good

performance Vegetable oils that formulated as alternatives to mixed paraffin oils

were well emulsified in water with surfactant system containing SLES and fatty

alcohols especially coconut oil In addition 2 wt MELs incorporating with cetyl

alcohol and glycerol monostearate formulated with coconut oil in water could

prepare cream with average maximum viscosity of (118plusmn08)times105 Pamiddots which is

comparable to that of system with 2 wt SLES instead

15

Declarations

No portion of the work referred to in the thesis has been submitted in support of

an application for another degree or qualification of this or any other university or

other institute of learning

i The author of this thesis (including any appendices andor schedules to this

thesis) owns any copyright in it (the ldquoCopyrightrdquo) and has given The

University of Manchester the rights to use such Copyright including for any

administrative purposes

ii Copies of this thesis either in full or in extracts and whether in hard or

electronic copy may be made only in accordance with the Copyright

Designs and Patents Act 1988 (as amended) and regulations issued under

it or where appropriate in accordance with licensing agreements which the

University has from time to time This page must form part of any such

copies made

iii The ownership of certain Copyright patents designs trademarks and other

intellectual property (the ldquoIntellectual Propertyrdquo) and any reproductions of

copyright works in the thesis for example graphs and tables

(ldquoReproductionsrdquo) which may be described in this thesis may not be owned

by the author and may be owned by third parties Such Intellectual Property

and Reproductions cannot and must not be made available for use without

the prior written permission of the owner of the relevant Intellectual Property

and or Reproductions

iv Further information on the conditions under which disclosure publication

and commercialisation of this thesis the Copyright and any Intellectual

Property andor Reproductions described in it may take place is available

in the University IP Policy in any relevant Thesis restriction declarations

deposited in the University Library The University Libraryrsquos regulations and

in The Universityrsquos policy on Presentation of Theses

16

Acknowledgements

I am very grateful to my supervisors Dr Thomas Rogers and Dr James Winterburn

for their careful guidance and useful advice throughout the project Thanks to my

seniors who gave me care and support in both of life and study to Ben Dolman for

his help with biosurfactant production to Sergio Carrillo De Hert for his training on

rheometer and Mastersizer to Sara Bages estopa for her training on surface

tension measurement Appreciate for the support of Reynard Spiess with mass

spectrometry measurement Thanks to University of Manchester for providing the

top educational resources for me

Last but not least I would like to sincerely express my appreciation to my parents

and my lovely fianceacute for their understanding all along this PhD period giving me

material and emotional support that are essential to rely on

17

Chapter 1 Introduction

11 Research System

Personal care and cosmetics include a wide variety of items that people commonly

get access to in their everyday life including for example shampoos and soaps

for cleaning skin creams and lotions for protecting and nourishing foundation and

lipstick for beautifying Occupying a large portion of market share around the world

cosmetic creams are served as necessities that applied by people for various

purpose which are multicomponent systems usually forming by two immiscible

liquids oil and water where one is dispersed in the other (Ying 2010) As

thermodynamically unstable systems having tendency to demix into two liquids

surfactants are usually applied in the formulation for facilitating emulsion formation

through adsorbing at the interface during homogenization and reducing the

interfacial tension to promote droplet dissociation (Khan et al 2011) In addition

as for the formulation of a cream namely semisolid emulsions mixed surfactant

system is largely applied instead of single surfactants consisting of different types

of surfactants or emulsifiers such as ionic or non-ionic ones combined with fatty

amphiphiles Researchers extensively studied the microstructure of oil in water

cream stabilized by a mixed surfactant system finding a general four-phase-

system presented as (Colafemmina et al 2020b)

a CrystallineHydrophilic gel phase consisting of bilayer of the mixed

emulsifier system and intralamellarly fixed water

b Lipophilic gel phase consisting of the superfluous co-emulsifiers which is

not aligned in the mixed emulsifier system

c Bulk water

d Dispersed oil phase which is immobilized by the lipophilic gel phase

The microstructure of multicomponent emulsion system is macro-reflected by its

flow property When the balance between thermal and interparticle forces reaches

an equilibrium the system is correspondingly in various states from the liquid-like

viscous microstructures with low resistant to external force to the semisolid-like

viscoelastic dispersions with three-dimensionally self-bodying structure exhibiting

as yield stress or storage moduli (Ha et al 2015) The original structure and

relevant properties will be altered and rebuilt when the system subject to an

external driving force where the introduced hydrodynamic forces interact with

thermal and interparticle forces leading to a sophisticated microstructure involved

18

melting or deforming and so on As one of the most significant characteristics of a

cream during production and application processes flow property is closely related

to the quality stability and efficacy of product Rheology is a subject that studies

the behaviour of flow and deformation of materials Being as a useful method for

cream production and improvement rheological characterisation help understand

the nature of system select raw materials and control manufacturing processes

(Tatar et al 2017) In addition the end use of creams could be predicted by

conducting rheological measurements from removing from the container to

applying on the skin As the success or failure of final products is greatly

determined by their flow properties rheological study is significant for the

improvement of manufacturing process and the development of customer-satisfied

products

In this project cream E45 was used as a standard model cream purchased from

Boots Sourcing from product label the ingredients of E45 shown in Table 11 were

classified based on their functions where the weight concentration of three key

components are specified according to its product introduction

Table 11 Classification of ingredients formulated in E45 cream based on function

12 Research Motivation

Surfactant system generally accounts for 10~20 wt of cream playing significant

roles in the production with which a three-dimensional gel structure will be formed

Traditional surfactants that widely applied in commercial cosmetic creams are

chemically synthesized and petroleum derived which have been suggested to be

ingredients Weight

concentration (wt)

function

White soft paraffin 145

Emollient skin lubricant moisturizer

Light liquid paraffin 126 Hypoallergenic anhydrous

lanolin 10

Glyceryl monostearate

Surface active compounds (emulsifiers

surfactants) Cetyl Alcohol

Sodium Cetostearyl Sulphate

Sodium Hydroxide

Neutralizing agents adjust acidbase balance Citric Acid Monohydrate

Carbomer Thickenerviscosity enhancerstabilizer

Methyl Hydroxybenzoate Anti-fungal agent preservative Propyl Hydroxybenzoate

Purified water

19

harmful to both of marine or land environment and human body due to their

hazardous origin and poor biodegradability (Mujumdar et al 2017) It has been

reported that petrochemical surfactants destroy the external mucous layer of

aquatic animals and cause damage to the gill of fishes Moreover some of them

will accumulate in the food chain which indirectly cause threat to human health

(Sajna et al 2015) In addition synthetic surfactants have great potential of

causing skin irritation as their close contact They denature proteins and strip lipids

in stratum corneum (SC) By penetrating through the SC layer synthetic

surfactants further pose a threat to cells in deeper skin layers and interfere with the

function of the cell membrane (Seweryn 2018) Especially ionic surfactants which

strongly bind to proteins due to electrostatic interactions exhibit more sever skin

irritation compared to non-ionic surfactants which interact with protein via weak

forces of hydrogen and van der Waals bonds (Mulligan 2005) As the increasing

of peoplersquos eco-friendly awareness surfactants that widely applied in industries are

expected to be ldquogreenerrdquo for the sake of environment and human beings Based

on this microorganism-derived biosurfactants are gradually drawn attention from

both of the academia and the industry for replacing those petroleum-derived

surfactants in products directly linked to human health such as food

pharmaceuticals and personal cares

13 State-of-the-Art

Surfactant is generally known as surface active ingredient which has been widely

studied and commercially applied since very long before With the development of

economy a sharp increase was witnessed in the production of surfactants since

early 20th century Up to today surfactants are already not simply applied for

cleansing but are multifunctional substances used for emulsifying dispersing

solubilizing defoaming and wetting in various fields such as petroleum industry

detergent industry environmental pollution treatment food industry personal care

industry and so on (Awad et al 2011) Owing a polar head group showing affinity

to water and a non-polar tail group having opposite affinity surfactant molecule

behaves amphiphilicity and functions at interfaces of wateroil or waterair to modify

the properties of the interface

For the surfactantsrsquo application in oil industry more recent studies focused on

surfactant flooding technique for tertiary phase of oil recovery known as enhanced

oil recovery (EOR) With combined mechanisms of surface activities including

interfacial tension reduction reservoir rock wettability alteration foam generation

20

and water-oil emulsification the optimised surfactant formulation was injected into

specific reservoir therefore minimizing capillary forces presented in oil production

and improving the overall oil displacement efficiency (Alsinan et al 2019) Those

mechanisms of different types of surfactants have been widely investigated The

interfacial tension reduction by non-ionic surfactants anionic surfactants

zwitterion surfactants and polymeric surfactants on oil-water interface were

assessed to be capable for their application for EOR More recently researchers

started to look at the possibility of using natural surfactants in EOR applications

for eco-friendly purposes Eslahati et al found that 4 wt of Saponin solution

helped increase the total oil recovery by 192 using spontaneous imbibition (A et

al 2020) And in another study during the tertiary oil recovery phase 521 of

original oil in place (OOIP) in reservoirs was recovered with 5g L-1 Saponin solution

added In the study of Dashtaki et al a natural surfactant was developed from

Vitagnus plant extract which obtained the OOPI recovery of 106 when 3000

ppm applied (Dashtaki et al 2020) In order to bypass the problem of alkalis

involvement when single surfactant applied mixed surfactant system was also

designed for EOR Surfactant-polymer system was formulated and helped achieve

recovery of 245~348 OOIP without alkali involved (Han et al 2019) also the

anionic and zwitterionic surfactant mixtures lowered oil-water interfacial tension

below 0001 dynes cm-1 leading to a displacement of 63~75 of residual oil which

could not be achieved by single surfactants (Han et al 2019)

In the field of pollution abatement surfactants are capable of dealing with

contaminated soil through mobilizing or solubilizing organic pollutants petroleum

hydrocarbons and heavy metals and enhancing the degradation of organic

contaminants known as chemical surfactant flushing technique which could be

carried out both in situ and ex situ (Ali et al 2017) The principles for the viability

of the technique focused on solubilisation of hydrophobic substances by

surfactants (Zhu 2011 Garciacutea-Cervilla et al 2020) behaviour of surfactants in

aqueous solution (Xia et al 2020 Jardak et al 2016 Li et al 2017) interactions

between different types of surfactants and pollutants (Sharma et al 2017

Katarzyna et al 2017) and for the improvement of the technique focused on

increasing surfactant efficiency (Naghash and Nezamzadeh-Ejhieh 2015 Hailu et

al 2017 Bankole et al 2017) optimizing the formulation of surfactant flushing

solutions have been extensively studied From the perspective of cost saving and

environmental protection more scientific researchers have found cheaper

alternatives for surfactant solutions in flushing processes such as surfactant foam

21

(Bertin et al 2017 Wang and Peng 2015 Karthick et al 2019 Li et al 2020)

colloidal gas aphron (Mukhopadhyay et al 2015 Zhang et al 2019b Aiza et al

2019) and so forth But this new subject is still need more studies to support its

perfect implementation in contaminated soil treatment

The study of application of surfactants in food pharmaceutical and cosmetic

industry has been extensively studied most of them focused on formulating high-

performance and innovative products through both theoretically and

experimentally analysing the roles of different types of surfactants on product

systems (Wang and Marangoni 2016 Drakontis and Amin 2020b) Still the

unique molecular structures endow surfactants with their ability to adsorb to the

interfaces self-assemble into micelles and further various structures of liquid

crystallines therefore playing significant roles in the formulation (McClements and

Gumus 2016) Emulsion-based products are ubiquitous in above mentioned

industries the system of which usually contains multiple components such as oil

water fragrances preservatives active ingredients and surfactants Thus it is

obvious to notice that the microstructure and interaction between those

components should be well designed in order to achieve a perfect product that

meets their required standards such as consistency texture appearance and

stability Researchers have already made efforts to clarify unique amphiphilicity-

based properties of surfactants that lays foundation for their potential applications

in actual product development including solubility micellization cloud point krafft

point adsorptivity and so on (Bnyan et al 2018 Song et al 2018 Pengon et al

2018 Shibaev et al 2019 Kirby et al 2017 Tao et al 2017 Tummino et al

2018) Also the synergistic effects of using mixed surfactant system surfactant-

polymer mixed system and surfactant-nanoparticle system have also been

characterised in some literature papers (Bera et al 2013 Kumari et al 2018

Sintang et al 2017 Kumar et al 2016 A et al Agneta et al 2019 Zhou et al

2019 Qian et al 2020 Fuzhen et al 2018 Ren et al 2019 Wang et al 2018d)

As for formulation technology more recent studies utilize the combination of

experiments and computer-aided tools such as simulations modelling and

thermodynamics to provide guidance and achieve optimal results when studying

the properties and phase behaviours of surfactants in specific systems instead of

traditional model-based and trial-and-error methods (Preux et al 2020 Chen et

al 2017b Ali et al 2018)

The large market share of surfactants directly demonstrates their widely industrial

application According to the report the global surfactant market revenue

22

generation was $413 billion in 2019 and is projected to reach $585 billion by 2027

growing at a CAGR of 53 from 2020 to 2027 (Pooja et al 2018) Similarly

another statistic analysis indicated that the global surfactants market is expected

to reach $524 billion by 2025 from $421 billion in 2020 at a CAGR of 45 from

2020 to 2025 (Markets and Markets 2020) Nowadays the surfactant market is

dominant by chemically synthesized surfactants which are mostly petroleum

derived It is the large scale usage of surfactants in industries that researchers

gradually pay more attention to their safety study Scientists found that the

presence of corrosive elements in the structure of synthetic surfactants and long

hydrophobic part consisting of C-C and -CH leads to their toxicity and unstable in

product systems (Lukic et al 2016) Sodium dodecyl sulfate (SDS) has been found

to have side effect on gastrointestinal tract And the presence of sulphur in SDS

boosts corrosive the existence of quaternary ammonium component in CTAB

inhibits the enzymatic activity the accumulation of hydrophobic moiety in Tween

20 destabilize the air and inhibits formation of stable foam (Guzman et al 2016

Lin et al 2016b)

At the same time the concept of ldquogreen chemistryrdquo always drives scientists and

engineers to seek for novel formulations that are more sustainable eco-friendly

and safer for both human and environment Microbial-based surfactants generally

known as microbial biosurfactants are the emerging sustainable alternatives for

their chemical synthetic counterparts It should be pointed out that in this thesis

ldquomicrobial biosurfactantrdquo will be simplified as ldquobiosurfactantsrdquo representing for those

surfactants that obtained through microorganisms metabolism or synthesis as

researchers indicated that the term of ldquobiosurfactantsrdquo has to be clarified because

some plant-based surfactants such as saponin are also named as biosurfactants

(Ahmadi-Ashtiani et al 2020)

Actually studies related to biosurfactants began in the 1960s and they are

gradually applied into industries in recent times Researchers have carried out

extensive investigations on biosurfactants in the aspect of detecting and screening

potential production microorganisms structural analysis physicochemical

properties characterisation media optimization for increasing the yield

improvements and innovation of fermentation and downstream technology and

their potentially industrial application (Spina et al 2018 Schultz and Rosado

2020)

23

Biosurfactants are promising as their high biodegradability low toxicity low

environmental impact structural diversity and high activity at extreme conditions

especially their human-friendly and eco-friendly natures (Schultz and Rosado

2020) Early in the 1990s rhamnolipids secreted by Pseudomonas aeruginosa had

been shown low toxicity compared to chemically synthesized ones (Kuyukina et al

2015) When comparing to synthetic surfactant ldquoMarlon A-350rdquo rhamnolipids

exhibited nontoxicity and non-mutagenicity (Irfan-Maqsood and Seddiq-Shams

2014) Gein et al found that glycolipid biosurfactant derived from Rhodococcus

ruber is non-cytotoxic towards human lymphocytes (Gein et al 2011) In a study

of Kim et al no inactivation of mouse fibroblast L929 cells was witnessed after 48-

hour exposure to a biosurfactant mannosylerythritol lipid (MEL-SY16) And

Pseudozyma spp-produced mannosylerythritol lipids (MELs) exhibited protective

effect on skin through activating the fibroblast and papilla cells (Kim et al 2002)

Vollbrecht et al carried out the irritation test on trehalose tetraester that produced

by Phodococcus spp 51 T7 and the chemically synthesized sodium dodecyl

sulfate (SDS) indicating less irritation of trehalose lipids against keratinocytes and

fibroblasts compared to chemical surfactant SDS (Kuumlgler et al 2014 Makkar et

al 2011) In the same aspect sophorolipids were also studied and displayed low

cytotoxicity on human keratinocytes (Lydon et al 2017) In addition 5~10 of

MELs (MEL-A solutions) have potential ability to moisturize human skin cells

suffering damage of a chemically synthesized surfactant The biodegradability

tests of biosurfactants have already been extensively conducted Rhamnolipids

were proved to be biodegradable under anaerobic and aerobic conditions showing

greater ability compared to Triton X-100 which only partially biodegrade under

aerobic conditions (Reddy et al 2018) In the study of Chrzanowski et al

biodegradability of rhamnolipids when being cultivated in different types of soils

were studied where the final results indicated degradability of 92 of total amount

of rhamnolipids in all soils after seven-days incubation (Liu et al 2018

Chrzanowski et al 2012) Candida bombicola-produced sophorolipids even

exhibited almost instant degradation after the production of the compound by

cultivating the strain (Goswami et al 2020 Minucelli et al 2017) Similarly in the

biodegradation study of MELs Candida antarctica-produced biosurfactant were

productively biodegraded by activated sludge microorganisms in five minutes or so

(Wada et al 2020 Saika et al 2017)

Over the past decades the commercial-scale of products that incorporated with

biosurfactants have been developed in a few companies A Belgian manufacturer

24

Ecover Eco-Surfactant formulated multi-purpose cleansing products using

sophorolipids that originated from Evonik (Germany) (Tang et al 2020) Soliance

(France) SyntheZyme LLC (USA) Kaneka Ltd (Japan) and Saraya (Japan) have

also applied sophorolipids for their application in detergents cosmetics and other

products (Hilares et al 2018) Kanebo Cosmetics Inc (Japan) have produced

Mannosylerythritol lipid B (MEL-B) applying in cosmetic industry (Adu et al 2020)

Rhamnolipids are widely produced in a range of companies such as Jeneil

biosurfactant (USA) Paradigm Biomedical Inc (USA) AGAE technologies Ltd

(USA) TeeGene Biotech Ltd (UK) Urumqi Unite Bio-Technology Co Ltd (China)

Rhamnolipids Companies Inc (USA) (Arauacutejo 2018) Nevertheless comparing to

the global production of surfactants which is expected to reach more than 24 million

tons annually by 2020 (Hrůzovaacute et al 2020) statistic research estimated the

biosurfactant production to be only around 462 kilo tons per year by then (Souza

et al 2018) indicating about 2~3 occupation in the annually global surfactant

production In addition market share of microbial-derived biosurfactants only

account for less than 01 of the global market despite some chemically

synthesized biosurfactants such as alkyl polyglycosides (APGs) and plant-based

biosurfactants take up 4 of the total (Roelants et al 2019b)

The commercialisation of microbial-derived biosurfactants is promising but also

need to expand by breaking through the bottleneck As reported the impediments

to the large-scale application of biosurfactants are mainly ascribed to their highly

money-consuming production process and sometimes low yield (Olasanmi and

Thring 2018) The price of biosurfactants is approximate 20 higher than

chemically synthesized surfactants (Silva et al 2019a) where 10 to 30~50

of the total cost of biosurfactants refers to feedstock and substrates and 60 to

70~80 of that arises from production aspect including biotechnology processes

and downstream strategies (Drakontis and Amin 2020a de Almeida et al 2019

Hrůzovaacute et al 2020) Thus more recent studies in this field aim to improve their

cost performance by investigating low-cost substrates which are from either

renewable or waste materials optimizing processes and selecting novel strains

for production enhancement Utilization of renewable substrates for biosurfactant

production was review by Banat et al (Thavasi and Banat 2019b) Cheap and non-

conventional substrates for strain cultivation were highlighted in their studies

including those from agro-industrial wastes and crop residues (Bran beet

molasses cassava rice hull of soy corn and sugar cane molasses) animal fat

wastes coffee processing residues (coffee pulp and coffee husks) plant oils (palm

25

oil and soybean oil) distillery wastes oil-containing wastes (coconut cake peanut

cake olive oil wastes soapstock and lubricating oil waste) food processing by-

products (frying edible oils olive oil and potato peels rape seed oil) fruit processing

by-products (pine apple carrot industrial waste and banana waste) (Borah et al

2019 Pele et al 2019 Devaraj et al 2019 Lima et al 2020 Verma et al 2020

Kezrane et al 2020 Louhasakul et al 2020 Das and Kumar 2019) Vecino et al

carried out biosurfactant production using vineyard pruning waste (VPW) as low

cost substrates where lingnocellulosic wastes were applied as carbon sources for

L paracasei consumption achieving two types of biosurfactants When growing

on glucose-based medium from VPW Lparacasei produced glycolipopeptide

while glycoprotein was achieved when the strain consuming lactose instead

(Thavasi and Banat 2019a) However researcher suggested that lignocellulose

feedstock is needed pre-treatment using fractionation strategy for enabling

cellulose saccharification (Wang et al 2020a Mota et al 2019) In another study

wood hydrolysates from birch and spruce woodchips were applied as glucose

source for rhamnolipids production by cultivating P aeruginosa DBM 3774

although the yield of rhamnolipids when applying renewable sources (231plusmn010 ~

234plusmn017 g L-1) was only about half of that when pure glucose (418plusmn019 g L-1)

was used as a carbon source (Hrůzovaacute et al 2020)

Animal fat combined with corn steep liquor was applied as carbon source for

glycolipid biosurfactant production by cultivating yeast Candida lipolytica UCP0988

where a maximum yield was achieved when comparing to other applied substrates

(Souza et al 2016) Whey the by-product of food processing is full of lactose (75

of dry mass) protein organic acids minerals and vitamins When growing

Streptococcus thermophiles Lactobacillus acidophilus and Lactobacillus

rhamnsus on medium of whey wastes biosurfactants were produced and exhibited

emulsifying inhibitory and antiadhesive properties (Soukoulis et al 2017 Santos

et al 2019 Jiang et al 2016) In the study of Kaur et al sophorolipids were

secreted by yeast Starmerella bombicola when consuming restaurant leftover food

waste as substrates and the yield was comparable to traditional cultivation (Kaur

et al 2019 Wang et al 2020b) In the study of Jadhav et al sunflower acid oil

refinery waste was applied as substrates for sophorolipids production using S

bombicola as production strain (Jadhav et al 2019) Also another report claimed

sophorolipid production by cultivating strain on residual oil cake medium (Jimeacutenez‐

Pentildealver et al 2020) Both of above two investigations determined the effective

emulsification ability of biosurfactants Very recently a biosurfactant extract was

26

obtained from waste stream of corn wet-milling industry showing capability for

increasing the stability of vitamin C in aqueous solution for cosmetic application

(Rincoacuten-Fontaacuten et al 2020)

From another aspect researchers also looked at various methods for increasing

the production of biosurfactants to further maximize their profit such as optimizing

media components and growth conditions applying modified strains through

metabolic engineering or altering their composition and the emerging recombinant

DNA technology (Jimoh and Lin 2019a) This technology refers to construct and

develop recombinant or mutilative hyperproducing microorganisms for increasing

biosurfactant yield also producing associated effective bio-products (Kandasamy

et al 2019) A bio-dispersant originated from a mutant defective Acinetobacter

calcoaceticus A2 was produced in a higher level and its further downstream

treatments including purification recovery and application were relieved due to the

less protein involved in the product (Saacuteenz-Marta et al 2015) Researches on

biosurfactants biosynthetic genes and enzymes are significant The heterologous

expression of surfactin synthetase genes was depicted from B licheniformis NIOT-

06 in the study of Anburajan et al and the modified strain can synthesize

biosurfactant at high rates (Anburajan et al 2015) Bunet et al proposed that the

polyketide synthases non-ribosomal peptide synthases and fatty acid synthases

could be activated by the cloned Sfp-type phophopantetheinyl transferases for bio-

synthesizing fatty acids and antibiotics (Bunet et al 2014) Similarly Jimoh and

Lin reported lipopeptide production through cloning of biosurfactant genes from B

subtilis SK320 and Paenibacillus sp D9 (Jimoh and Lin 2019c) In addition to that

they also studied the optimization of medium and growth conditions for lipopeptide

production using Paenibacillus sp D9 where effect of carbon nitrogen carbon to

nitrogen ratio metals supplementation pH temperature and inoculum size on the

production have been thoroughly investigated (Jimoh and Lin 2019b) Earlier than

that another study was carried out by Parthipan et al analysing similar conditions

for B subtilis A1 cultivation to produce lipopeptide (Parthipan et al 2017) Except

experimental path Kiran et al carried out statistical model based optimization of

media components in order to obtain lipopeptide through cultivating Brevibacterium

aureum MSA13 where full-factorial central composite design was applied (Kiran

et al 2010) Mnif et al applied statistical model of Box-Behnken design for media

components optimization where B subtilis SPB1 was cultivated to produce a

biosurfactant (Mnif et al 2013) The glycolipid mannosylerythritol lipids was

27

secreted by P aphidis ZJUDM34 growing on a medium that optimised using

statistical model (53)

As for downstream processes complex mixtures of biosurfactant after

manufacture and molecular variants of microbial-derived surfactants could make it

harder if specific species is required Organic solvent extraction was proved to

achieve high yield of biosurfactant but hazard and toxic chemicals harming human

and environment health is inevitable compensated for this strategy More recent

studies focused on applying new biosurfactant recovery method for the production

such as gravity separation (Dolman et al 2017 Dolman et al 2019) foam

fractionation (Bages-Estopa et al 2018 Najmi et al 2018) On top of that some

novel biotechnologies supported energy-saving production processes Perfumo et

al suggested the production of low-temperature biosurfactants through cultivating

cold-adapted microorganisms where no heat was required during the cultivation

therefore introducing a low-energy-demand process of biosurfactant production

(Perfumo et al 2018)

Properties characterisations of biosurfactants along with their potential application

have been extensively studied which provides its high possibility for their

commercialisation In personal care industry the demand for biosurfactants in

personal care is expected to reach 507 kilo tons by 2020 accounting for more

than 10 of total biosurfactant market which is in the second place just after 446

occupation of the market by household detergent growing at a CAGR of 45 from

2014 to 2020 (Pham et al 2018) Bezerraa et al studied the comparison of

emulsifying properties between vegetable-based (Chenpodium quinoa) and

microorganism-derived (Pseudomonas aeruginosa) biosurfactants for their

application in cosmetic industry (Bezerraa et al 2020) As a result higher

emulsification index of oils when biosurfactant originated from P aeruginosa was

used as emulsifier which reached 71 (oil of rosemary) whereas C quinoa-

derived biosurfactant maximally led to 51 emulsification index of coconut oil In

addition both of biosurfactants were stable until the temperature was up to 100degC

and their resistance to pH variation was also studied where vegetable-based

biosurfactant remained stable within pH rang of 4~8 and that for microorganism-

based biosurfactant was within pH range of 6~10 Also another research was

carried out introducing the potential application of biosurfactant in cosmetic

industry where a biosurfactant extract combined with Tween 80 in a shampoo

formulation was applied for the stabilization of Zn pyrithione in tea tree oil with

28

water emulsion An optimal formulation was proposed giving the emulsion good

stability of 91 after 30 days achieving highest solubility of Zn pyrithione of 59

(Lukic et al 2016)

Very recently a lip gloss of water-in-oil emulsion was formulated using different

concentrations of rhamnolipids and sophorolipids as stabilizer showing a stable

product via rheological analysis However silica particles were involved in the

formulation for building up the viscosity in the continuous phase and larger

diameter size of silica particle imparted a more rigid network (Drakontis and Amin

2020b) Resende et al studied the formulation of toothpastes incorporating

biosurfactants that produced by P aeruginosa Bacillus methylotrophicus and

Cbombicola combined with chitosan that extracted from fungus Mucorales where

properties of toothpastes were analysed including pH foamability cytotoxicity

and antimicrobial action and the results showed comparable to commercial

products (Resende et al 2019) Similarly another mouthwash formulation

involving biosurfactants also presented lower toxicity comparing to commercial

ones (Farias et al 2019) Some researchers found the possibility of formulating

Lactobacillus paracasei derived biosurfactants in essential oils and natural

antioxidant emulsified in water for enhancing the stability of the emulsion (Ferreira

et al 2017 Vecino et al 2016) therefore providing new eco-friendly cosmetic

formulations

The application of biosurfactants in pharmaceutical industry mainly focused on

drug delivery improvements and their abilities of antimicrobial anti-adhesive

antiviral anticancer anti-inflammatory and immunomodulatory (Rodriacuteguez-Loacutepez

et al 2019 Sandeep and Rajasree 2017 Janek et al 2019 Adu et al 2020) It

has been suggested that sophorolipids with amino acids presented antibacterial

activities against gram-positive and gram-negative organisms anti-HIV and anti-

spermicidal activities (Xu et al 2019) Also sophorolipids have been proved to

help in wound healing and dermatological care through binding to silk fibroin

protein therefore accelerating its gelation (Maxwell et al 2020) Lactoacilli spp-

and marine bacteria-produced biosurfactants all exhibited effective anti-biofilm

activity against S aureus CCM 3953 and P mirabilis CCM 7188 (Englerovaacute et al

2018) In food industry researchers recently proposed the application of glycolipids

as food additives and preservatives in formulations due to their anti-biofilm and

antioxidant activities (Merghni et al 2017 Nataraj et al 2020) A glycolipid

produced via cultivating Saccharomyces cerevisiae URM 6670 in a medium

containing agricultural by-product was incorporated into the cookie dough

29

formulation as the substitute for egg yolk presenting an excellent thermal stability

and comparable properties of firmness and elasticity to standard formulation

(Ribeiro et al 2020) From another aspect by-products in food industry could be

converted to high value substances during biosurfactants synthesis (Satpute et al

2017) realizing the same goal as growing microorganisms on waste or renewable

substrates for biosurfactant production Kiran et al found a biosurfactant producing

strain which was isolated Nesterenkonia sp from a marine sponge Fasciospongia

cavernosa and proposed the biosurfactant as a potential food addictive (Kiran et

al 2017) In a recent study rhamnolipids were investigated in terms of their

activities in different conditions showing their antibacterial ability in food usage by

controlling the growth of pathogens but pH alteration and basic conditions may

hinder its application (de Freitas Ferreira et al 2019) Another glycolipid

sophorolipids that extracted from Calbicans and C glabrata exhibiting excellent

antibacterial activities against B subtilis and E coli This providing their potential

as emulsifiers and antibacterial agents applying in food industry (Gaur et al 2019)

Through the mechanisms including increasing substrate bioavailability for

microorganisms interacting with the cell surface to increase cell surface

hydrophobicity for easily associating hydrophobic substrates with bacterial cells

biosurfactants are capable of applying in environmental bioremediation (Karlapudi

et al 2018) Researchers have found the application of biosurfactants for

removing heavy metal contaminants (Tang et al 2017 da Rocha Junior et al

2019 Chen et al 2017a Lal et al 2018 Sun et al 2020) treating wastewater

(Bhosale et al 2019 Ndlovu et al 2016 Damasceno et al 2018 Guo and Gao

2020) cleaning up oil spill and other aspects (Shah et al 2019 Patel et al 2019

De Souza et al 2018) It has been reported that adding rhamnolipids with

concentration higher than CMC value enhanced solubilisation of petroleum

components leading to an increase of biomass growth from 1000 to 2500 mg L-1

and 40~100 of diesel biodegradation (Mostafa et al 2019) In addition a few

marine bacterial strains were reported to have the potential application for

biosurfactant production when consuming hydrocarbons (Xu et al 2020) thus

proving the possibility of using biosurfactants in marine environment abatement

For soil bioremediation Pseudomonas aeruginosa W10 secreted biosurfactant

W10 effectively biodegraded polycyclic aromatic hydrocarbons (PHAs) including

phenanthrene and fluoranthene (Chebbi et al 2017) Similarly glycolipids

obtained from Pseudomonas sp MZ01 has been applied for PHAs elimination

through electrokinetic-microbial remediation (EMR) method (Lin et al 2016a)

30

Another research was conducted using lipopeptide (Paenibacillus dendritiformis

CN5-derived) for removing PHA indicating that higher concentration of lipopeptide

(600 mg L-1) enhancing the biodegradation of pyrene (Hanano et al 2017)

Bacillus Acinetobacter Sphingobium Rhodococcus and Pseudomonas Spp

isolated from polluted soil all presented total petroleum hydrocarbons removal

ability (up to 50) after seven-days incubation in peptone medium from beef

extract (Wang et al 2020c) The application of biosurfactant for oil recovery is

highly promising where crude product or even the whole cell broth could be used

due to no requirements for the purity thereby economizing on downstream

processing Nocardia rhodochrous produced trehalose lipids increased total oil

recovery from underground sandstone by 30 (Le Roes-Hill et al 2019)

Traditional EOR could be enhanced through involving biosurfactants production

process resulting in microbial enhanced oil recovery (MEOR) technique Specific

microbes tailored to oil reservoir are involved in MEOR experiencing metabolic

events and facilitating biosurfactants synthesis therefore enhancing oil recovery

(Purwasena et al 2019)

14 Research Objectives and Aims

This project primarily aims to provide information for formulation design of personal

care creams incorporating with biosurfactants with understanding of the

production process and the effect of replacing the surfactant As standard models

for comparison lab-made mimic creams formulated with simplified surfactant

system that modified from commercially available E45 cream would be helpful

The objectives of the project are

1 to produce biousurfactants using fermentation technology and characterise

their structure

2 to formulate mimic creams and bio-creams with the system of respective

containing chemically synthesized surfactants and biosurfactants with mixed

paraffin oils in water for understanding the effect of surfactant alteration on

cream performance

15 Overview of Thesis

Chapter 1 described the project background aims and objectives Chapter 2 serve

as literature reviews related to the concepts involved in this project Chapter 3

31

illustrated the methodology and corresponding theories that has been used in the

project Chapter 4 and Chapter 5 respectively described the characterisation of

commercial E45 cream and production of mimic creams containing different

concentrations of SLES Chapter 6 discussed the effect of manufacturing process

on the performance of creams Chapter 7 presented the results of biosurfactants

production and their structural analysis The final chapter 8 exhibited the

production of bio-creams that formulated with biosurfactants and discrepancies

between bio-creams and mimic creams in terms of their property variations

16 Nomenclature

Specific nomenclatures that applied in this thesis are indicated in the text For

supplementary some of frequently used nomenclatures are listed here

Sodium lauryl ether sulfate SLES

Cetyl alcohol CA

Glycerol monostearate GM

Sophorolipids SLs

Mannosylerythritol lipids MELs

Biosurfactants BSs

32

Chapter 2 Literature Review

In this chapter concepts relating to the project are introduced in details including

chemically-synthesized and bio-derived surfactants cream formulation and

rheology

21 Surfactants

Surfactants are known as surface active agents that reduces the surface or

interfacial tension of a solvent and changes interfacial condition of the system

thereby playing a key role in wetting emulsifying foaming solubilizing dispersing

and so on Due to these functions surfactants are wildly used in households

personal cares foods pharmaceuticals and various fields (Kumari et al 2018)

It has been studied that the surface tension of aqueous solutions will be changed

with the variation of solution concentrations presenting three type of dependence

as shown in Figure 21 (Hiemenz 1986) Most organic solutes lower the surface

tension at water-air interface by adsorbing at the surface resulting in exhibition of

attracted forces between molecules at surface due to weaker intermolecular forces

of organic solute (compared to that of water) and larger intermolecular distance of

molecules at surface (compared to that in bulk liquid) while inorganic electrolytes

remaining in bulk solution tend to slightly increase the surface tension because the

interaction between attractive ion and water molecules in the bulk leads to

destabilize water interaction at surface (Boyer et al 2017)

Among organic solutes surfactants (Green curve in Figure 21) are able to sharply

reduce surface tension within low concentration range before the concentration

surf

ace

ten

sio

in

concentration of component

surfactant solutes

inorganic electrolytes

Figure 21 Dependence of surface tension on the concentration of various solutes

33

reaching a critical value and there is no further reduction afterwards (Mittal and

Shah 2013)

211 Structure of Surfactants

The surfactant molecule consists of a water-favouring hydrophilic head group

comprising charged ion group or uncharged polar group mainly determining

different types of surfactants and an oil-favouring hydrophobic tail moiety which is

usually an alkyl chain with or without side chain (Mitru et al 2020) This unique

amphiphilic structure of surfactant molecules determines its ability in reducing the

surface and interfacial tension of different phases Figure 22 shows the general

diagram of a surfactant molecule

212 Classification of Surfactants

Based on the molecular mass surfactants are classified into low molecular mass

surfactants and polymeric surfactants In respect to low molecular mass

surfactants differences of ldquotailrdquo moieties between different surfactants are not

significant but hydrophilic ldquoheadrdquo group is of great varieties Anionic cationic non-

ionic and amphoteric surfactants are four main categories of petroleum-derived

surfactants which are classified according to the nature of their head groups (Peffly

et al 2016)

a) Cationic surfactants

The hydrophilic head group of cationic surfactant molecules dissociates cations in

aqueous solutions Most commercially valued cationic surfactants are the

derivatives of organic nitrogen compound having positive ion charge carried by

nitrogen atom such as amine salt cationic surfactant and quaternary ammonium

cationic surfactant (Ozkan et al 2020) Some examples of quanternary

Hydrophilic head

(Polar)

Hydrophobic tail (Non polar)

Figure 22 Schematic diagram of surfactant molecule

34

ammonium coumpounds (QAC) and corresponding chemical structures are listed

in Table 21

Table 21 Examples of cationic surfactants and corresponding chemical structures

Name and Structure

Stearalkonium

Chloride

Cetrimonium

Chloride

Dicetyldimonium

Chloride

In personal care industry QACs are one of the most effective classes of cationic

surfactants (Falbe 2012) Due to carried positive charge QACs have an

advantage in antistatic applications Based on this they are wildly used in hair care

products for softening hair and making it easy to rinse (Pati and Arnold 2020) A

research (Ran et al 2009) has been done to investigate the adsorption kinetics of

dimethylpabamidopropyl laurdimonium tosylate (DDABDT) onto the corneum of

scalp in which the wettability of hair fibers changed from hydrophobic to

hydrophilic with the concentration of DDABDT only increasing from 005 mmol L-1

to 015 mmol L-1 Also the formation of bilayer structure is responsible for the

enhancement of the wettability application

Besides QACs are also frequently used as antibacterial agents In the study of

Nakata et al (Nakata et al 2011) after treating the bacterial Escherichia Coli cell

with cetyltrimethylammonium bromide (CTAB) a state of superoxide and hydrogen

peroxide generation was witnessed This indicates that the generation of

superoxide in the cell becomes the main reason for the antibacterial function of

cationic surfactant But it has not made clear that how superoxide and hydrogen

peroxide generated in the cell treated by CTAB Regarding to stearalkonium

chloride and cetrimonium chloride a patent has claimed that the combination of

these two QACs in the formula offers an advantageous of minimizing the total

35

amount of usage of QACs thus the manufacturing cost of personal care products

will be decreased (Verboom and Bauer 2003)

b) Anionic surfactants

In slightly acidic neutral or alkaline aqueous solutions the hydrophilic lsquolsquoheadrsquorsquo

groups of anionic surfactants are negative charged for example carboxylates

(alkane carboxylate salts) alkane sulfate esters sulfonates (alkane-aromatic

sulfonic acid salts) and phosphoric acid esters In aqueous solutions anion head

group forms a structure with counter ions such as Na+ or K+ (Caracciolo et al

2017) Examples of anionic surfactants are listed in Table 22 including most

frequently used functional groups of anionic surfactants and the corresponding

representatives

Table 22 Examples of anionic surfactants and corresponding chemical structures

By ionization anionic surfactants increase the negative potential of the interface

between substance and granular dirt enhances the repulsive force between

substance and dirt (Li and Ishiguro 2016) Therefore they have good effects on

removing granular dirt and preventing it from redepositing It has been reported

that anionic surfactants such as linear alkylbenzene sulfonates and alkyl sulfates

Type Name and Structure

Carboxylates

(-COOM)

Sodium Stearate

C17H35-COO--Na+

Sulfonates

(-SO3M)

Sodium Dodecyl Benzene Sulfonate (SDBS)

C18H29-SO3--Na+

Sulfate

esters

(-OSO3M)


C16H33-O-SO3--2Na+

36

are normally used in heavy duty detergents (Tai et al 2018) Besides it can also

be used as an emulsifier in different types of cosmetic creams food industry and

pharmaceutical fields such as Triethanolamine salt of dodecyl benzene sulfonic

acid (TDS) which showed the ability to stabilize the oil in water emulsion (Zhang

et al 2017b)

Carboxylated salts are a subgroup of carboxylates generally applied as cleansing

agents for hand wash skin cleansers shaving products and so on The typical

product is soap which is metal fatty acid (Sharma 2014) Sodium stearate a very

common carboxylate anionic surfactant is used in various commercial products

such as the brand LUSH and other brandsrsquo soap product

Sulfate surfactants (R-SO3M) are soluble in water and also have a good effect on

cleaning emulsifying and foaming The most common used products are alkyl

sulfates alkyl ether sulfates amide ether sulfates and alkyl glyceride sulfates

(Tiwari et al 2018) Properties of alkyl sulfates depend on their chain length and

the degree of branching of the hydrocarbon chain Although presenting excellent

foaming properties and widely being applied in cosmetics shampoos and skin

cleansers relatively sever irritation of alkyl sulfates to human skin is nonnegligible

(Seweryn 2018) Thus even though alkyl sulfates are the most commonly used

type of anionic surfactants in various personal care products their safety still

remains controversial From this aspect amide ether sulfates with magnesium

salts are promising alternatives showing good skin compatibility also with perfect

foaming ability providing a potential surfactant for mild personal care cleansing

formulation (Ananthapadmanabhan 2019) Compared to sulfate compounds

sulfonates are suggested as anionic surfactants with less irritation The linear alkyl

benzene sulfonate (LAS) is one of the most common used sulfonates (Tai et al

2018) Due to its better solubility stronger decontamination and lower cost LAS

plays an important role in detergent industry (Metian et al 2019 Ziacutegolo et al 2020)

c) Non-Ionic Surfactants Surfactants

Non-ionic surfactants do not dissociate into ions in an aqueous solution Their

hydrophilic moieties are made up of a number of oxygen-containing groups such

as ether group or hydroxyl group which can form hydrogen bonds with water to

implement dissolution (Porter 2013) The classification of non-ionic surfactants

depends on the type of their hydrophilic moiety Common types are fatty alcohols

ethoxylated fatty alcohols alkylphenol ethoxylates alkyl polygycosides

37

ethoxylated fatty acids alkyl carbohydrate esters amine oxides and so on (van Os

et al 2012)

Compared to ionic surfactants non-ionic ones have a higher stability which is not

susceptible to the existence of strong electrolyte inorganic salt (Deyab 2019)

Thus they are capable of being used in hard water due to the invulnerability of

Mg2+ and Ca2+ In addition they exhibit excellent effect on emulsifying and

solubilizing such as alcohols and esters that are commonly applied in personal

care industry Another significant characteristic of non-ionic surfactants is their

good skin compatibility maintaining their dominant application in products for

sensitive skin or baby skin However as weak foaming ability non-ionic surfactants

are generally applied as emulsifier combing with ionic surfactants or other

stabilizers in formulations (Shubair et al 2020 Zhang et al 2018a)

In the formula of cosmetic cream cetyl alcohol stearyl alcohol and glycerol

monostearate are normally used to help emulsify and stabilize the product Besides

Spans and Tweens are two common non-ionic surfactants that are reported to

perform much better than ionic surfactants (Koneva et al 2017) Table 23

presents chemical structures of representative non-ionic surfactants

Table 23 Example of non-ionic surfactants and corresponding chemical structures

Name and Structure

Cetyl

alcohol

Glycerol

mono-

stearate

Sorbian

mono-

stearate

(Span 60)

Polyethylene glycol sorbian mono-stearate

(Tween 60)

38

d) Amphoteric surfactants

The hydrophilic group of amphoteric (zwitterionic) surfactants carry both of positive

and negative charge such as RN+(CH3)2CH2COO- They dissociate into anions

and cations based on the pH in aqueous solution (Guzmaacuten et al 2020 Ren et al

2017) thus neither like ionic surfactants that only adsorb on a positively charged

surface followed by changing it into cationic surface nor the cationic ones that only

adsorb on a negatively charged surface and change it into positive one amphoteric

surfactants are capable of adsorbing on both positively and negatively charged

surfaces without alter surface charge (Yarveicy and Haghtalab 2018) Due to their

versatile properties amphoteric surfactants are gradually applied in various

industries as an alternative to other type of surfactants In recent amino sulfonate

amphoteric surfactants attract attention among researchers due to their different

properties from conventional amphoteric surfactants that endowed by their unique

molecular structure consisting of one or more latent cationic centres and a small

range of isoelectric points (Ren et al 2017) Ren et al studied the mixed surfactant

system consisting of an amino sulfonate amphoteric surfactant (C12AS) that

carried two positive charges on its hydrophilic head group and a non-ionic

surfactant (OP-n) providing an agreement between critical micelle concentration

value of the system predicted using molecular-thermodynamic method and that

obtained from experimental work with deviation due to hydrophilicity of the

micellization of nonionic surfactant (Ren 2017) Also different co-solvents are

applied to study the micelllization More recently a study carried out micellization

and interfacial properties analysis of system consisting of C12AS and different

types of alcohols of 70 g L-1 and further explained the electronic delocalization

structure of C12AS molecule presented at air-liquid interface or in bulk phase

laying theoretical fundamental for their industrial applications (Huang and Ren

2020)

39

213 Surfactant Behaviour in Water Solution

When surfactant molecules dissolve in aqueous solutions surfactants experience

the process of self-assembly and different structures are gradually formed from

the initial monomers to micelles and then liquid crystals

2131 Monomers

When dissolving in water surfactant molecules align at the surfaces or interfaces

and form monolayers (Saad et al 2019) Figure 23 shows diagram of the

alignment of different types of surfactant molecules at water surface

Surfactants exhibits various surface or interfacial activities where surface tension

reduction is the basic representative for identification of the presence of a

surfactant in the solution Through surfactant molecules adsorbing and

accumulating at surfaces some of water molecules in the surface are replaced by

surfactant molecules and forces of attraction between surfactant and water

molecules are less than those between two water molecules thus the contraction

force is reduced leading to the reduction in the surface tension (Hantal et al 2019)

From another aspect the alignment of surfactant monomers at the surface reduces

the increased system free energy that caused by the dissolution of single

surfactant molecule in water thereby maintaining the stability of the system

(Rehman et al 2017)

After monomolecular film at surface is saturated surfactant molecules begin to

migrate into bulk liquid The individual surfactant molecule that presented in the

air

water

a) cationic

b) anionic

c) Non-ionic

d) Amphoteric

(Take Spans as an example)

Figure 23 schematic diagram of different types of surfactant molecules alignment at water surface

40

volume phase of solution is known as monomer which is in constant motion Thus

the consistent exchange between monomers in solution and that aligned at the

surface help minimize interactions between water molecules and hydrophobic

groups of monomers in solution (Saad et al 2019) Surfactant monomers are also

directly associated with the occurrence of skin irritation through adsorbing on the

skin surface interacting with the stratum corneumrsquos keratin protein causing

denaturation of its α-helix structure (Morris et al 2019b) Rhein et al presented

the work showing that the severity of skin irritation was high during skin exposure

to surfactant solution before critical micelle concentration was achieved where

surfactants in volume phase are in the form of monomers (Rhein 2017)

2132 Micelles

Further increasing surfactant concentration in the solution results in the self-

assemble and aggregation of monomers After a specific concentration known as

critical micelle concentration (CMC) is exceeded the aggregate structures namely

micelles are formed (Kelleppan et al 2018) The value of CMC varies depending

on different surfactant types The formation of micelles in solution is caused by

hydrophobic effect of surfactants interacting with water molecules with their

hydrophobic groups displaying molecule clusters with hydrophilic groups towards

solvent molecules to protect hydrophobic moieties in the core from contacting with

solution (Ramadan et al 2018)

The size of the micelle (micellar weight) is usually measured using light-scattering

method and the number of associated molecules in the micelle could be calculated

by dividing micellar weight with surfactant molecular weight which is determined

by surfactant molecular shape (Ritter et al 2016) Within low concentration range

the number of molecules only depend on the environment conditions It has been

reported that higher temperature leads to larger micelles of non-ionic surfactants

whereas when the concentration of counter ions increases in solution ionic

surfactant forms larger micelles (Hu et al 2019)

Simple surfactant molecules with a single alkyl chain boned to a large polar head

group generally form spherical or oval micelles with a packing factor (VlmiddotS) of less

than 13 (V represents for the volume of a single surfactant molecule l indicates

molecular length and S is the surface area occupied by a molecule) (Manohar and

Narayanan 2012) Change in concentration results in a micellar shape difference

Take sodium dodecyle sulfate (SDS) as an example when the concentration of its

41

solution reaches CMC (0008 mol L-1) spherical micelles forms when the solution

concentration increases to 10 times of CMC rod-shaped micelles forms Further

increasing the concentration of SDS solution will aggregate rod-like micelles

together to form hexagonally packed rod micelles eventually forming palisade

layer micelles (Bang et al 2010)

Depend on different type and structure of surfactants the shape of micelles that

they form varies Cylindrical micelles showing packing factor of 13~12 are

formed by one-chained surfactants with a smaller polar group or ionic surfactants

in the presence of electrolyte (Xu et al 2018) While double-chain surfactants with

a large hydrophilic head group and flexible chains tend to form vesicles or

bimolecular structures (VlmiddotS = 12~10) and when a small head group is boned to

two chains that are stiff planar or stretched micelles (VlmiddotS = 10) are formed

instead Reverse micelles (Vl middotS gt 10) are formed if two-chained surfactants

connected with a small polar head group and large non-polar head group

((Faramarzi et al 2017 Manohar and Narayanan 2012)

2133 Liquid Crystals

Liquid crystalline phases are usually involved in the surfactant system formulated

in structured fluids where concentration of surfactant is high enough and micelles

aggregate together forming distinct structures (Jing et al 2016) The shape

structures and optical properties of liquid crystrals (LCs) are different from micelles

As seen in Figure 24 where schematically presents the change of phase

conditions in the surfactant solution depending on the temperature and

concentration surfactants of concentration higher than CMC are preliminary

crystal hydrates (insoluble) when temperature is below the phase transition

temperature Tc Increasing the temperature over Tc leads to molecular soluble

phase gradually changing from spherical micelles to rodlike micelles with

concentration increased further forming lyotropic LCs with the relocation and

aggregation of micelles (Guo et al 2018)

42

Liquid crystals (LCs) are matters in mesomorphic state which show the properties

of both liquid and solid (Guo et al 2010) Phases of LCs that usually formed are

hexagonal LCs (H1 and H2) cubic LCs nematic LCs and gel phase (Lβ)

intermediate phase lamellar phase (Lα) LCs

Lamellar phase (Lα) lays fundamention for other structured phases which involves

bilayers of surfactant molecules trapping abundant interlamellar water in between

Lamellar phase is originated from coagels which is in a bilayer structure (trans-

zigzag) of hydrated solids at low temperature then through a gel phase (Lβ) where

the temperature is over Tgel (gel phase transition temperature) but below Tc Almost

no water exists between hydrophilic groups of coagels while Lβ behaves the same

trans-zigzag structure but involves plenty of water in between No alignment of

hydrocarbon chains is found in Lα imparting lamellar phase more flexible and

easier to move thus the viscosity in lamellar phase is lower than that in gel phase

This property is applied in the formulation of cream products where cooling helps

transfer Lα to Lβ achieving a more rigid product (Kim et al 2020a)

LCs that self-assembled from surfactant molecules have been wildly used in food

cosmetic oil exploration and many other aspects related to peoplersquos daily life

which should be given more attention in the following research Some researchers

have proved that the liquid crystalline phase in the cosmetic emulsion exerts the

Tem

pe

ratu

re H

igh

Surfactant concentration High

Critical

Micelle

Concentrati

on (CMC)

Hydrated Solid (Lamellar Structure)

Molecular

soluble phase

Krafft

Point

So

lid

Are

a

Micelle Solution

Phase Liquid Crystal Formation

Area

Middle Phase

(Hexagon

form)

Lamellar

Phase

Cubic

Phase

Tc boundary

Cloud Point

boundary

Liquid-liquid

phase Separation

Spheric

Micelle

s

Rodlike

Micelle

s

Figure 24 Dependence of structure and phase formation on the surfactant concentration and temperature adapted from Guo et al 2018

43

advantage of stabling the emulsion and increasing its viscosity through

surrounding dispersed droplets and acting as barriers to prevent coalescence or

structuring the three-dimensional network in continuous phase to inhibit the

mobility of droplets (Racheva et al 2018 Terescenco et al 2018a Chellapa et

al 2016) LCs in emulsions are capable of combining with water oil or other active

ingredients (Kulkarni 2016) where combined water is generally in two forms when

LCs exist in an emulsion interlamellarly fixed water (bound water) and bulk water

(free water) Bound water in emulsions tends to improve the moisturising properties

of the product due to the low evaporation rate of interlamellarly fixed water (Savic

et al 2005) Through analysing an alkyl polyglycoside stabilized emulsion it has

been suggested that LCs were formed during the cooling stage and the lamellar

liquid crystal structure provided a good spreadability to the product (Terescenco et

al 2018b) Besides it has been reported that increasing the liquid crystal structure

in an emulsion helps reduce the transepidermal water loss indicating the hydrating

effect of LCs on the emulsion (Zhang and Liu 2013)

44

22 Bio-surfactants

Bio-surfactants (BSs) natural surface active agents are synthesized by a range of

microorganisms Possessing the similar structure as chemically synthesized

surfactants their molecules also consist of both hydrophilic part which comprise

an acid peptide cations or anions mono- di- or polysaccharides and hydrophobic

portion which comprise unsaturated or saturated hydrocarbon chains or fatty acids

(Silva et al 2019c) Although most BSs are regarded as secondary metabolites

they play a significant role in promoting microbial growth BSs are secreted by

microorganisms which in turn have the ability to enhance the consumption of

nonpolar and undissolved hydrocarbon substrates by microorganisms through

adjusting the hydrophobicity of microbial cell surface (Yang et al 2012)

BSs possess advantages over chemically synthesized surfactants in terms of low

toxicity high biodegradability high resistance to extreme environment and

excellent surface activity (Singh et al 2019) Many BSs are claimed with

bactericidal activity and this advantage is exerted in the activity of bacteria gliding

through interface and during the metabolic process tolerating environmental

extremes (Sana et al 2018) The aggregate forming capacity generally presented

with critical micelle concentration (CMC) is an indicator for surfactant efficiency

Specifically lower CMC value endows a surfactant powerful surface activity To

some extent CMC value of BSs are proved to be much lower than that of a few

chemically synthesized surfactants In the study of Bharali et al CMC of the BS

secreted by P aeruginosa JBKI was around 540 mg L-1 and produced by strain

S5 was 965 mg L-1 (Bharali et al 2014) which were lower than CMC value of

chemically synthesized surfactants such as sodium dodecyl sulphate (SDS) with

CMC of 2010 mg L-1 (Wang et al 2018c) tetradecyl trimethyl ammonium bromide

(TTAB) with CMC of around 2000 mg L-1 (Whang et al 2008) cetyltrimethyl

ammonium bromide (CTMAB) with CMC of 322 mg L-1 Triton X-100 with CMC of

181 mg L-1 (Liang et al 2014) B subtilis ATCC 21332 produced surfactin was

capable of reducing surface tension to 279 mN m-1 with CMC value of 45 mg L-1

(Silva et al 2010) Similarly lipopeptides from Bacillus sp ZG0427 showed high

surface activity by lowering surface tension of water to 246 mN m-1 with CMC of

50 mg L-1 (Hentati et al 2019) Both of them are powerful than chemical synthesis

surfactant sodium lauryl sulfate which was reported as decreasing surface tension

to 565 mN m-1 (Hamed et al 2020 Bhattachar et al 2011) In addition

researchers found the surface activity of BSs has close relationship with their

purification process (Silva et al 2010) It has been studied that crude

45

biosurfactants that produced by strain FLU5 decreased surface tension of ultra-

pure water from 72 to 34 mN m-1 while purified lipopeptides further lowered the

value to 28 mN m-1 (Hentati et al 2019)

221 Classification of Biosurfactants (BSs)

Biosurfactants (BSs) are classified according to their microbial sources chemical

structure production method and applications Basically five categories are

identified based on different structures neutral lipids glycolipids lipopeptides

phospholipids and polymetric bio-surfactants (Sobrinho et al 2013 Shah et al

2016)

In addition according to molecular weight Rosenberg and Ron (Rosenberg and

Ron 1999) divided the microbial surface active compounds into BSs (low

molecular weight) and bio-emulsifiers (high molecular weight) The low-molecular-

weight BSs such as glycolipids phospholipids and lipopeptides are applied for

lowering the surface and interfacial tension while the bio-emulsifiers such as

polysaccharides lipopolysaccharides proteins are more capable of stabilizing

emulsions (Satpute et al 2010) In Table 24 representative BSs examples are

listed (Shoeb et al 2013)

Table 24 Classification of bio-surfactants adapted from Shoeb et al 2013

Type of BSs Examples

Low mass BSs

Glycolipids

Rhamnolipids Sophorolipids

Mannosylerythritol lipids

Trehalolipids

Lipopeptides and

lipoprotein

Surfactin Gramicidin S

Polymyxin

Phospholipids fatty acids

and Neutral lipids Phosphatidyleth-anolamine

High mass BSs

Polymeric BSs Emulsan Bio-dispersan

Liposan mannoprotein

Particulate BSs Vesicles and fimbriae

Wholecells

Glycolipids are one of BSs that have been deeply studied Regarding to their

structure long-chain fatty acid is linked by a covalent bond to carbohydrates

where alkyl of fatty acid constitutes the hydrophobic group and saccharide makes

46

up the hydrophilic group (Caffalette et al 2020) Not only possessing excellent

surface activities glycolipids also have various functions such as antioxidant

emulsification foaming washing dispersion and antistatic which makes them as

a promising alternative to chemically synthesized surfactants in various fields such

as food pharmaceutical and cosmetic industries (Onwosi et al 2020)

222 The Production and Extraction of Biosurfactants (BSs)

BSs can be produced via three methods microbial fermentation enzymatic

synthesis and natural biological extraction Most biological surface active

compounds are secreted by bacterial yeast or fungus Different microorganisms

produce different types of BSs under different conditions and researches have

screened different types of microorganisms that are capable of producing BSs with

various structures (Nayarisseri et al 2018 Wang et al 2017 Hassan et al 2018

Кайырманова et al 2020) Compared to microbial fermentation enzymatic

synthesis is an organic reaction where exogenous enzymes are used to catalyse

bio-surfactant synthesis Through this production process BSs of simplified

structures and single varieties are produced due to the selectivity of enzyme

(Enayati et al 2018 Marcelino et al 2020 Torres et al 2020) Natural biological

extraction refers to the extraction of effective BSs from natural bio-ingredients To

exemplify this phospholipid and lecithin are also BSs that derived from egg yolks

and a soybean However due to the limitation of raw materials this method is

hardly applied in a large scale production (Wan et al 2017)

At present mainly due to high cost of production and purification of BSs it cannot

deny that the replacement of chemically synthesized surfactants by microbial BSs

that produced through fermentation for commercial use is still difficult although the

efficacy of BSs in lab-scale and small-volume production has been extensively

manifested It has been reported that the high yield of rhamnolipids is greatly

determined by the usage of hydrophobic substrates which is relatively more

expensive than those hydrophilic ones (Varjani and Upasani 2017) indicating the

high cost of raw materials for their large-scaled production Thus as stated

previously more recent researchers started to carried out fermentation with

renewable and inexpensive substrates for strain cultivation (Dalili et al 2015) In

addition to that downstream process contributes the most to the higher operational

cost of BSs production due to the sometimes their low concentration and unique

amphiphilic nature with various structure making it difficult for separation them from

medium broth (Moutinho et al 2020) Chemical solvent extraction and

47

vaporization are the most widely used technique that reported to help reach the

maximum BSs recovery rate but this conventional method is high-priced and

energy-intensive also with a tendency to cause irreversible damage to producing

cell (Dolman et al 2017) In addition chemical solvent extraction is not feasible

for the commercial-scale production of BSs due to the large productivity

benchmark of no less than 2 g L-1h-1 is required (Roelants et al 2019b) As an

alternative path to that a reverse extraction was recently proposed for

rhamnolipids separation where alkaline aqueous solution (equimolar NaOH to

rhamnolipids) was used for their back extraction achieving 97 of total

rhamnolipids recovery in aqueous phases (Invally et al 2019) Integrated

separation methods are of great interests as their ability for higher productivity and

yield such as gravity separation foam fraction and membrane separation

Gravityndashbased integrated separation method is emerging that help overcome

drawbacks of low production and costly extraction process As suggested in the

study of Dolman et al where a fermentation of highly viscous sophorolipids

production yielded volumetric productivity of 062 g L-1h-1 the integrated recovery

method controlled oxygen limitation during production and alleviated inhibition for

genes biosynthesis caused by continuously produced sophorolipids with high

viscosity thereby enhancing productivity and yield (Dolman et al 2017) Moreover

the technique was successfully applied in a pilot scale working volume of

fermentation (30 L) indicating the possibility of wider application of in situ gravity

separation method in BSs extraction process Compared to this a two-stage

separation system was proposed by Zhang et al where applying a novel

bioreactor with dual ventilation pipes and dual sieve-plates in the fermentation

achieved higher productivity of 159 g L-1h-1 but this configuration obviously

increased the cost (Zhang et al 2018b) Other methods such as crystallization

and precipitation combining flotation standing rotary vacuum filtration and

centrifugation to remove cell pellet are also reported in literatures Acid

precipitation is frequently used for rhamnolipids recovery from broth medium

followed by solvent extraction and chemical evaporation As stated in a study

applying alcohol precipitation for biopolymer removal prior to normal acid

precipitation for rhamnolipid extraction increase the purity from 66 to 87 before

further extraction process (Invally et al 2019) More recently the integrated foam

fractionation method wass widely studied especially for rhamonolipid extraction

(Jiang et al 2020) as the technology has the ability to alleviate foaming problem

specifically liquid foam during fermentation process by continuous isolating

rhamnolipids from broth medium (Heyd et al 2011) which could be promoted by

48

introducing foam breaker with perforated plates for further enhancing foam

destabilization (Liu et al 2013) But more efforts are needed for its large-scale

application due to the complexity of the configuration However extraction

methods are established specific to the type and nature of BSs For example

flotation and standing are not applicable for separating BSs that produced by

bacterial cell (Daverey and Pakshirajan 2010) Regarding to new technologies for

BSs extraction ultra-filtration is one of the most effective ones Using ultrafiltration

membrane with molecular weight cut-off (MWCO) of 10000 (YM210) to extract

rhamnolipids the yield reaches 92 Also the yield of 80 and 58 was obtained

when using ultrafiltration membrane with MWCO of 30000 (YM230) and 50000

(YM250) respectively (Pereira et al 2012)

223 Characterization of Biosurfactants (BSs)

BSs could be characterized by several conventional methods such as thin layer

chromatography (TLC) mass spectrometry (MS) and high performance liquid

chromatography (HPLC) in order to study their structures and properties (Ndlovu

et al 2017 Ankulkar and Chavan 2019 Ong 2017)

Mass spectrometry is usually applied to identify the structure of different BSs The

principle of this technology is that the chemical species are ionized and then the

ions are classified according to the mass-to-charge ratio Conducting mass

spectrometry measurement the structure of dirhamnolipids (Rha-Rha-C10-C10)

was identified from the Rhamnolipid where the rhamnolipid was extracted using

21 chloroformmethanol solvent mixture (Rahman et al 2002) High performance

liquid chromatography (HPLC) is proved to be an effective method used for the

detection of BSs and even their separation This measurement system is made up

of mobile phase stationary phase and a detector The commonly used detectors

are evaporating light scattering detectors UV refractive index and so on During

the measurement the sample is carried by mobile phase flowing over the

stationary phase which is a solid where components are separated and pass

through the detector successively Then the detector records the data and gives

the response in terms of each peak on a chromatogram For determining

rhamonolipids structure HPLC measurement was carried out where the

Supelcosil LC-18 column was used with a CH3CNTHF (5545 vv) mobile phase

at the flow rate of 075 ml min-1 The result was detected through a UV detector at

the wavelength of 225 nm The following anthrone analysis compensated for the

49

inaccurate result from HPLC before which Rhamnolipids were acid hydrolyzed to

avoid the presence of carbon substrates (Chayabutra and Ju 2001)

224 Application of Biosurfactants (BSs) in Various Fields

BSs have a great potential in application in a wide range of fields such as

petroleum exploitation pharmaceuticals industry cosmetic industry food industry

and agriculture (Kiran et al 2017 Patowary et al 2018 Santos et al 2017

Ribeiro et al 2019 Adu et al 2020 Xu and Amin 2019 Bai and McClements

2016)

In the field of oil recovery microbial- enhance oil recovery (MEOR) is proposed as

a cost-effective and eco-friendly technique in replacement of conventional

enhanced oil recovery (EOR) that heavily consumes chemical synthesized

surfactants resulting in relatively high cost (Ribeiro et al 2020) MEOR is

implemented by introducing indigenous or exogenous microorganisms in

reservoirs for the production of metabolites (BSs) that are capable of demulsifying

and separating oil-water mixed system in order to optimize oil production from

existing reservoirs and recycle waste crude oil for reprocessing or energy recovery

in petroleum industry (Yang et al 2020) Cultivating strain Azotobacter vinelandii

AV01 was reported to produce BSs which showed ability of emulsifying the crude

oil up to 90 leading to a 15 increase in the recovery efficiency of crude oil

(Helmy et al 2010) Similarly Salehizadeh et al have done another research and

found that the BSs produced by Alcaligenes faecalis MS103 showed 107

increase of the crude oil recovery efficiency (Salehizadeh and Mohammadizad

2009) More recently rhamnolipid secreted by different microorganisms showed

excellent performance in oil recovery application The efficacy of MEOR by

rhamnolipids was evaluated through cultivating Pseudomonas aeruginosa that

isolated from artificially contaminated soil with crude oil achieving an optimal result

that rhamnolipids with concentration of 100 (higher than its CMC which is 127

mg L-1) effectively recovered 1191 plusmn039 of oil with API gravity of 2190 (Cacircmara

et al 2019)

Although lots of efforts have been made to screen aerobic functional

microorganisms for their ex situ application in MEOR and investigate the oil

recovery efficiency of ex situ production of BSs (Haloi et al 2020 Saravanan et

al 2020) where BSs are externally produced and then injected into oil reservoir

in situ application of BSs in MEOR is proposed to be more beneficial compared to

that for their cost effective without transportation and complex configurations for

50

BSs production (Du et al 2019) But this process is relatively disadvantageous if

aerobic microorganisms are used due to additional air pumping in the reservoirs

leading to higher cost poorer operation and lower safety (Zhao et al 2015) Thus

microorganisms that are capable of producing BSs under anoxic conditions are

required Zhao et al identified Pseudomonas aeruginosa SG that isolated from

Xinjiang oil field as a promising strain that could produce rhamnolipid under anoxic

condition by consuming various type of organic substrates In their study an extra

833 of original crude oil in the core was extracted through in situ production of

rhamnolipid by the strain (Zhao et al 2015) but the production was inhibited by

H2S which is produced from sulfate-reducing bacteria (SRB) widely existing in the

petroleum industry Thus introducing a recombinant Pseudomonas stutzeri Rhl

helped effectively remove H2S and at the same time produce rhamnolipids under

S2- stress below 333 mg L-1 (Zhao et al 2016)

Glycolipids possess strong medicinal activity which can be used to prepare tablets

including semi-synthetic penicillin and macrolide antibiotics This can increase the

load of drug in blood per unit time thereby facilitating the drug absorptivity of

digestive system (Nguyen et al 2010) BSs also plays an important role in

bioremediation The contamination of industrial waste water solid wastes

pesticides heavy metal and other pollution sources has become increasingly sever

to water body and soil and BSs produced by microorganisms help improve the

hydrophilicity and bio-accessibility of hydrophobic compounds which displacing

pollutants into environment with continuously degradation (Kreling et al 2020)

In food industry BSs favours for their application as antimicrobial and anti-biofilm

agents foaming agents wetting agents emulsifiers food additives and so forth

(Rai et al 2019) The emulsifying activity of BSs has been extensively evaluated

with different oils or hydrocarbons In a study of sophorolipids production from

yeast strain Candida albicans SC5314 and Candida galabrata CBS138 their

emulsifying ability was determined against castor oil with the emulsification index

of 51 and 53 separately for C albicans and C glabratag providing their ability

as food emulsifiers In addition the stability of sophorolipids were confirmed within

a wide range of pH (2~10) and temperature (4~120 degC) as well as salt

concentration (2~14) (Gaur et al 2019) In addition lipopeptide BSs and

rhamnolipids were confirmed to form stable emulsions with various oils such as

soybean oil coconut fat and linseed oil (Nitschke and Pastore 2006) showing

high potential of application in food industry Similarly a glycolipid that produced

by cultivating marine bacteria Kluyveromyces marxianus FRR1586 on lactose-

51

based medium was able to emulsify corn oil in water and stabilize the system at

pH varying from 3 to 11 and salt concentration varying from 2 to 50 g NaCl L-1

(Fonseca et al 2008) Marine strain Enterobacter cloacae was identified for

producing bioemulsifier which showed excellent ability to enhance viscosity of

acidic solution confirming its application in food industry (Dubey et al 2012) In

addition to emulsify and stabilize the system BSs could be food additives for

improving the texture and consistency of dairy products by preventing

aggregations of fat droplets In the study of Mnif et al more cohesive texture of

dough was obtained when adding a lipopeptide BS in the formulation than that

formulated with soy lecithin resulting in a higher quality of bread (Mnif et al 2013)

Similar result was also achieved when incorporating sophorolipids in bread

formulation where the bread volume was increased and desirable appearance

was presented Owning antibacterial ability BSs are capable of keeping food safe

to use Lipopeptide BSs including lichenysin pumilacidin iturin gramicidin S and

polymyxins that produced by Bacillus sp were proposed in large amount of

studies for their application in foods (Coronel Leoacuten et al 2016 Saggese et al

2018 Kim et al 2020c Wenzel et al 2018 Nirosha et al 2016)

Apart from above mentioned functions of BSs in food industry surfactants of

microbial origin could be alternatives for chemical surfactants in the formulation of

nano-sized delivery system (Nirosha et al 2016) the molecules of that self-

aggregate to form unique structures trapping hydrophobic or hydrophilic

compounds within the structural core thereby forming microemulsions

nanoparticles and liposomes It has been studied that sophorolipids and

rhamnolipids were capable of forming biocompatible microemulsions when mixing

with lecithins in system (Nguyen et al 2010) Rhamnolipids was demonstrated to

facilitate partition of ω-3 polyunsaturated fatty acids for preparing emulsion-based

fish oil delivery system (Liu et al 2016) In another study for developing drug

delivery system of vitamin E a self-emulsifying system of high quality was

established when having surfactin in the system showing higher emulsification

efficiency dissociation rate and oral bioavailability (Nirosha et al 2016) which

indicates the merits and potential of applying BSs in food industry

225 Potential Cosmetic-applicable Biosurfactants (BSs)

The application of surfactants is significant in cosmetic industry especially for

biosurfactants owing to their low toxicity antibacterial property moisturising

capacity to skin The mechanisms of interaction between surfactants and skin have

52

been studied When surfactant monomers damage the secondary and tertiary

structure of stratum corneum (SC) through adsorbing on skin surface SC may

expose sites for binding water molecules and become swelling Also SC keratin

protein may be degraded and washed from the skin as well as solubilizing lipid of

the intercellular cement within the SC Longer-term interaction may lead to

penetration of surrounding stimulus such as chemical compounds and pathogens

to deeper SC layers for inducing living cellsrsquo immune response showing as topical

red on skin or itching (Seweryn 2018) Researchers found that both surfactant

monomers and micelles exhibited irritation to skin as the irritation activity was

detected when the CMC was exceeded Some of them attributed this to the

disintegration of micelles into monomers after contacting with skin while other

researchers claimed it may because smaller-sized submicelles were formed

(Morris et al 2019b) Also when the surfactant concentration was over CMC

significant increase of skin irritation effect caused by sodium dodecyl sulfate (SDS)

was witnessed where micelles that formed were small to easily penetrate into hair

follicle orifices while the lower increase was presented when ethoxylated sodium

dodecyl sulfate was involved (Cohen et al 2016)

However opposite to those synthetic surfactants BSs of natural origin comprising

of sugars lipids and proteins that are compatible with skin cells membrane Thus

they are not only pose no threat to living organisms but they generally have

antioxidant and antibacterial effects on skin exhibiting promising efficacy for

application in skin care products BSs of plant origin such as phospholipids have

various benefits in cosmetic product such as improving the dispersibility of

cosmetics maintaining skin moist and adjusting acidity of skin (van Hoogevest and

Fahr 2019) And sucrose ester takes advantage in improving washing property of

cosmetics increasing skin smooth and tender (Laville et al 2020) As for microbial

BSs Vecino et al evaluated the antimicrobial and anti-adhesive activities of

glycolipopeptide that produced by lactic acid bacteria (ldquoGenerally Recognized As

Saferdquo by the American Food and Drug Administration) showing that approximately

50 mg mL-1 glycolipopeptides exhibited antimicrobial activities against

Pseudomonas aeruginosa streptococcus agalactiae Staphylococcus aureus

Escherichia coli Streptococcus pyogenes and Candida albicans (Vecino et al

2017) Similarly another study also investigated the cell-bound glycoprotein that

produced by Lactobacillus agilis CCUG31450 5 mg mL-1 of which inhibited growth

of Staphylococcus aureus Pseudomonas aeruginosa and Streptococcus

agalactiae (Gudintildea et al 2015) In addition to that the antimycotic activity of

53

sophorolipids that obtained from Rhodotorula babjevae strain YS3 against

dermatophytes was in vitro and in vivo evaluated indicating that the biosurfactant

effectively treated dermatophyte by interacting with the cell membrane of pathogen

and disturbing the membrane integrity although only one resistance strain T

mentagrophytes was investigated (Sen et al 2020)

Glycolipids may be the most frequently used type of biosurfactants in the

formulation of personal care products due to their multifunctional properties

Generally they consist of aliphatic acids or hydro-xyaliphatic acids and a

carbohydrate group (Lukic et al 2016) Two attractive glycolipids sophorolipids

(SLs) and mannosylerythritol lipids (MELs) that has potential in skin care products

formulation will be introduced in details

2251 Sophorolipids (SLs)

SLs are non-ionic biosurfactants (BSs) that having various effects on personal care

products such as emulsifying detergency wetting defoaming and most

significantly biocompatible to human with low toxicity exhibiting high potential of

application in cosmetic industry Sophorolipids (SLs) is suggested to be affinitive

with human skin which is capable of acing as a humectant to keep skin moist also

it can be used in the manufacture of detergent It has been reported that SLs of 1

mol L-1 are highly affinity with skin which can be used as an excellent moisturizer

(Pekin et al 2005) A Japanese company has applied SLs in various cosmetic

products such as conditioner emulsion and lipstick as a moisturizer using Sofina

as its trade name Also the fermentation procedure of SLs has been studied by

this company and industrialized (Mujumdar et al 2017) From another Japanese

company Saraya SLs have also been commercially produced and used as

cleaning agents in cosmetics catering and dry cleaners (Kim et al 2020b) In

addition SLs also play a role in the production of baby skin care products by a

France company named Soliance (Baccile Nassif et al 2010)

22511 Structures and Properties of Sophorolipids (SLs)

The SLs is mainly produced by yeasts which is naturally a mixture of SLs

molecules with different structures These SLs molecules all consist of hydrophobic

and hydrophilic moieties Among them hydrophilic part is sophorose which is the

diglucose combined with belta-1 2 glycosidic bond and hydrophobic group is

made up of saturated or unsaturated long chain omega- (or omega-1) hydroxylated

fatty acid (Gaur et al 2019) These two parts is connected by belta-glycosidic bond

54

The structures of SLs molecules are mainly varied in two aspects which are

acetylation and lactonization (Figure 25) The diglucose hydrophilic part of SLs

molecules may either contain acetyl groups at the 6rsquo andor 6rsquorsquo positions or not the

carboxylic end of fatty acid of hydrophobic group can either be free acidic form

(open form) or internally esterified (closed ring) at the position of 4rsquorsquo 6rsquo or 6rsquorsquo

(carboxylic group of fatty acid esterified reacts with hydroxyl group at the 4 rsquorsquo 6rsquo or

6rsquorsquo) Other differences of structures are the hydrophobic group including length of

carbon chains (generally contain 16 or 18 carbon atoms) saturation and the

position of hydroxylation (Kim et al 2020b) SLs with various structures show

different physicochemical properties Lactonic SLs possess better surface

properties and antibacterial activities while acidic forms show better foamability

and solubility The lactonization decreases the atomic free rotation angle thereby

easily forming the transparent crystal However acidic SLs tends to exist in the

form of viscous oil (Van Bogaert et al 2011) Besides although the introduction

of acetyl groups decreases the solubility of SLs the antiviral property will be

enhanced

Lactonic Sophorolipid

55

It has been reported that the surface tension in water can be reduced from 73 mN

m-1 to 30~40 mN m-1 by SLs and the CMC value was 40~100 mg L-1 In addition

CMC value of SLs has a correlation to carbon chain length of fatty acid Specifically

the longer carbon chains the SLs had the lower the CMC value it presented

(Minucelli et al 2017) In the study by Zhang et al where SLs akyl (methyl ethyl

and butyl) esters were synthesized by chemically modification of SLs CMC value

was reduced by halving the introduction of one ndashCH2 to the akyl group of SLs akyl

ester This also manifests that the biodegradability is enhanced with the increase

of carbon chain length of molecules of SLs derivatives (Zhang et al 2004) Shin

et al also found that the SLs methyl ester containing oleic acid (C18) is more

difficult to biodegrade than that containing erucic acid (C22) (Shin et al 2010)

22512 Production of Sophorolipids (SLs)

When cells enter stationary phase SLs begin to form generally after being

inoculated 24~48 hours During stationary phase of cells SLs are well produced

It has been reported that 10 days is an optimal value for the whole process for SLs

production (Van Bogaert et al 2011) As extracellular glycolipids SLs are

produced by a number of microorganisms includes Candida apicola Starmerella

bombicola Torulopsis bombicola Candida bombicola Candida Batistae Candida

stellate Candida riodocensis where Candida bombicola is the most wildly applied

which produces SLs of the highest yield (Konishi et al 2018) Researchers have

also discovered novel producing strains such as Candida keroseneae GBME-

R1=R2=Ac Diacylated SLs

R1=R2=H Non-acylated SLs

R1=H R2=Ac R1=AcR2=H Monoacylated SLs

Acidic Sophorolipid

Figure 25 General structure of sophorolipids (SLs)

56

IAUF-2 Issatchenkia orientalis Meyerozyma guilliermondii YK32 and Candida

rugose for SLs production (Roelants et al 2019a Ganji et al 2020) through

screening surface active ingredients in environmental isolates using different

methods such as haemolytic activity drop-collapse assays and mostly applied

biochemical data analysis But misidentification occurred of producing strains when

assigning names of novel described BSs producers only according to biochemical

data As reported a novel SLs producer named Wickerhamiella domercqiae var

SL in the study of Chen et al was identified based on BIOLOG analysis showing

excellent SLs productivity while it was realized that no dissimilarity of their whole

genome sequences compared to previously described S bombicola sequences

(Ma et al 2014 Li et al 2016) Apart from that it was suggested that molecular

techniques can applied for yeast species identification (Silva et al 2019b) For

instance Nwaguma et al isolated BSs producing yeast from oil palm and Raphi

palm identifying six promising producers as Candida haemulois SA2 Pichia

kudriavzevii SA5 SB3 SB5 SB6 and SB8 using molecular and phylogenetic

evolutionary methods (Nwaguma et al 2019)

a) Substrates

Two types of substrates are needed in the production of SLs hydrophilic (glucose

or sugar-rich molasses) and lipophilic substrates (oil alkanes fatty acids or fatty

esters) but SLs can still be produced if both substrates are not simultaneously

contained in the medium even though the combination results in the highest yield

(Van Bogaert et al 2014) As found in a study the production from the media

containing both glucose and Turkish corn oil (40 g L-1) was higher than that

containing Turkish corn oil as the sole carbon source (30 g L-1) (Pekin et al 2005)

Also when the concentration of carbon source decreased the SLs may be

decomposed to supplement the strain with carbon source For instance S

bombicola restarted produce fatty acids for SLs production consuming more time

and energy compared to the process where hydrophobic substrates initially added

(Shah et al 2017) Based on this controlling the concentration of hydrophilic and

hydrophobic carbon sources has a crucial effect on improving the SLs yield

Glucose of 100 g L-1 is generally used as hydrophilic carbon source in the

fermentation medium for SLs production which is also suggested as the best value

Less SLs were produced when cultivating cells on 200 g L-1 or 300 g L-1 glucose

(Joshi-Navare et al 2013) Some hydrophilic carbon sources have been tried

such as sucrose galactose and lactose deproteinized whey as the replacement

57

of glucose but the yield of SLs was relatively lower than that with glucose (Jadhav

et al 2019)

The hydrophobic carbon source can be alkane fatty acid or oil Through comparing

the influence of different hydrophobic carbon sources to SLs production fatty acid

methyl esters or ethyl esters that derived from vegetable oils were superior to the

corresponding vegetable oils and both of them had an advantage over alkanes

(Shah et al 2017 Ma et al 2020) Oleic acid is a kind of free fatty acid with

specific carbon length which can achieve a relatively high SLs yield (Solaiman et

al 2007) Due to vegetable oil containing the oleic acid which is the most suitable

for SLs formation it can facilitate the production Rapeseed oil is an ideal vegetable

oil substrate (Kim et al 2009) The effect of alkanes on SLs production depends

on their carbon length When using hexadecane (C16) heptadecane (C17) or

octadecane (C18) to cultivate stains the production of SLs is higher than using

other hydrophobic carbon sources The possible reason for this may be that they

can directly transform into hydroxyl fatty acid and then integrated into SLs

molecules (Ma et al 2020 Habibi and Babaei 2017 Ashby and Solaiman 2019)

This direct conversion mode of alkanes obviously affects the composition of fatty

acid chain in SLs mixtures Hydrophobic substrates also have an influence on the

SLs composition There is an equilibrium of the proportions of lactonic and acidic

forms in SLs mixture which is affected by substrate species especially the type of

hydrophobic carbon sources (Shah et al 2017 Konishi et al 2018) To exemplify

this 85 of lactonic forms SLs was produced when using n-hexadecane as the

substrates while only 50 of that was produced when soybean oil was used

(Callaghan et al 2016) Also when using fatty acid esters or the by-product of

biodiesel as the substrates more acidic SLs were produced

Nitrogen source is also required for the production where the yeast extract of 1~5

g L-1 is often used However that the time for entering the stationary phase should

be determined by the limitation of nitrogen for instance higher carbon nitrogen

ratio (CN ratio) ensured the SLs formation by specific strains (Callow et al 2016

Da Costa et al 2017 Sanchuki et al 2017) Other compositions in medium such

as non-essential nutritional source citric acid buffer substances and inorganic ions

(Mg2+ Fe3+ and Na+) are sometimes included in the medium for strain cultivation

and appropriate amount help enhance SLs production

b) Biosynthesis Pathway

58

In the biosynthesis pathway of SLs production glycolipid and fatty acid chain are

mainly involved Target yeasts begin to synthesize SLs from the hydroxylation of

fatty acid Fatty acid is obtained either directly from media or from hydrolysis of

triglyceride or fatty acid methyl ester by extracellular lipase (Ma et al 2020)

Another indirect method to achieve fatty acid is cultivating yeast cells with a

medium containing alkane Candia bombicola is able to growth in the media that

has alkane as the only carbon source This means that intracellular enzyme that

catalyses the terminal oxygenation of alkane stepped oxidizes alkane to

corresponding fatty acid (Yang et al 2019) When no hydrophobic carbon source

is provided in the media fatty acid will be formed through de novo synthesis which

starts from acetyl-coenzyme A (COA) derived from glycolysis pathway The de

novo synthesis has been confirmed by the related research about Cerulenin which

is the inhibitor of fatty acid synthesis (Van Bogaert et al 2008)

After fatty acid transfers to hydroxyl fatty acid two active UDP-glucose molecules

are added to the hydroxyl fatty acid consecutively Glucose in medium is not

directly used for SLs production but only go through glycolysis path to complete

gluconeogenesis which is necessary in the formation of SLs (Minucelli et al 2017)

This explains that the head group of SLs will not be altered by changing the

provided different types of saccharides also SLs can still be produced even if

under the condition of no glucose or other polysaccharide involved that can

degrade to glycolipid (Saerens et al 2011)

c) Fermentation Parameters

The production of SLs is affected by various fermentation parameters Generally

the optimal growth temperature of C bombicola is 288 ordmC However 21 ordmC was

determined to be the optimal temperature (Elshafie et al 2015 Goumlbbert et al

1984) Most widely used temperature in literatures ranging from 25 ordmC to 30 ordmC

and no big difference of SLs yield was witnessed Nevertheless the biomass

increment is lower and the utilization of glucose is higher when cultivating the cell

at 25 ordmC (Pulate et al 2013)

Different pH value in broth can influence the type of SLs that produced It has been

found that when the pH value is 35 lactonic SLs was the major product from C

bombicola cultivation (Ciesielska et al 2016) In addition it has been discovered

that C apicola mainly produced acidic form of SLs when the pH value was lower

than 20 and when adjusting the pH value to 30 more lactonic SLs were formed

(Konishi et al 2018) The pH value of fermentation broth decreases sharply during

59

exponential phase In order to maintain the cell growth and increase SLs yield

NaOH solution frequently added into the broth for maintaining pH value at 35

(Delbeke et al 2016) In addition lower pH values that maintained during

fermentation process can reduce the potential of bacterial contamination

Dissolved oxygen is an important factor that will influence SLs production Due to

the highly viscous of SLs that continuously produced during fermentation tending

to hinder oxygen dissolving and inhibit cell growth much longer time will induce

lower production effectiveness for a single batch of fermentation Apart from that

the cell growth during exponential phase and the biosynthesis of SLs will be

affected where low oxygen supply has potential for limiting biological activity but

no effect on fermentation if a threshold was exceeded (Almeira et al 2015) A

study manifested that the optimal oxygen supply was between 50 to 80 mM O2 L-1

H-1 in terms of oxygen transfer rate (Guilmanov et al 2002) In the study of Pedro

et al the optimal aeration rate was investigated as 030 L kg-1 min-1 achieving an

optimized solid-state fermentation process for SLs production by cultivating

Starmerella bombicola on a residual oil cake substrate also no further increase of

SLs yield with higher aeration rate supplied as the threshold of oxygen air flow was

exceeded (Jimeacutenez-Pentildealver et al 2016) SLs containing saturated fatty acid will

be mainly achieved when lower oxygen dissolved in the broth (Elshikh et al 2017)

d) Extraction and Purification

Due to the density difference between SLs and the media it can be preliminary

separated from media by decanting after natural sedimentation or centrifugation

as proposed gravity-based separation method in the study of Dolmann et al

(Dolman et al 2017) Solvent extraction is a frequently used method for SLs

further purification usually with the help of ethyl acetate followed by vacuum rotary

evaporation to get rid of the solvent in the product (Ma et al 2011) Many methods

have been conducted to separate SLs into different specific structures according

to their physiochemical properties As reported lactonic SLs was soluble in ethanol

and the solubility was increased with the temperature rising while the acidic SLs

was slightly soluble in ethanol and the solubility may not change with temperature

(Ashby and Solaiman 2019) Thus the lactonic SLs can be extracted firstly by

dissolving the SL product in ethanol at high temperature and then cooling down

the solution to crystallize lactonic forms But this method has the potential of losing

lactonic SLs in ethanol Based on different solubility in water especially high pH

water where acidic form is soluble and lactonic SLs is insoluble Hu et al

separated acidic and lactonic forms in phthalates and phosphate buffers This

60

method has the advantages such as no use of organic solvent and relatively high

recovery (Hu and Ju 2001)

2252 Mannosylerythritol lipids (MELs)

Mannosylerythritol lipids (MELs) not only has favourable emulsifying capacity

biodegradability and other high surface activity it also has antimicrobial activities

such as inducing cell differentiation and cytometaplasia and strong coordinate

ability with glycoprotein (Banat et al 2010) Thus it has great potential for applying

in the field of cosmetics food and pharmaceutical industry

22521 Structures and properties of MELs

MELs generally contain 4-O-β-D-mannopyranosyl-erythritol as the hydrophilic

head group attaching to fatty acid chains as hydrophobic group There are four

different structures of MELs according to the number and position of the acetyl

group on mannose or erythritol it can be classified as MEL-A (diacetylated) MEL-

BMEL-C (monoacetylated at C6 position and C4 position respectively) and MEL-

D (deacetylated) (Niu et al 2017) The structure of MELs is schematically shown

in Figure 26 The structure includes three moieties mannopyranosyl (in red circle)

erythritol (in orange circle) and acyl chain (in blue circle) (Niu et al 2019)

61

Different strains tend to produce MELs with different structures Ustilago maydis

DSM4500 mainly produce MEL-A Pseudozyma antarctica tends to produce the

mixture of MEL-A MEL-B and MEL-C where MEL-A dominate the product

accounting for 70 (Saika et al 2018a) In addition cultivating same strain under

different fermentation conditions leads to the synthesis of different types of MELs

Pseudozyma parantarctica Pseudozyma Antarctica and Pseudozyma rugulosa

produced MELs (including MEL-A MEL-B and MEL-C) while when consuming 4

wt olive oil and 4 wt mannose as carbon source a new surfactant was

synthesized named MML (Morita et al 2009a)

Due to the difference in chirality of carbon atom in erythrityl a variety of diversity

of MELs structures exist including many kinds of diastereoisomers A new type of

extracellular MELs diastereomer has been reported by Fukuoka et al through

cultivating Pseudozyma crassa In the study the structure of the new MELs is

similar to that of MEL-A MEL-B and MEL-C but the stereostructure of erythritol is

totally different which is 4-O- β-D-mannopyranose-(2R3S)-erythritol Also

compared to the general medium resulted fatty acid chain partial short fatty acid

chain (C2 or C4) and long fatty acid chain (C14 C16 or C18) are attached to

mannosyl moiety leading to different properties of the product (Fukuoka et al

2008) By cultivating Pseudozyma antarctica and Pseudozyma rugulosa in the

consumption of soybean oil as carbon source Kitamoto et al produced MELs with

high hydrophobic property containing three acetyl group (Morita et al 2013)

O O

CH2

C

C

CH2

OH

OH

H

H OR1

CH3

CH3

R2

O

MEL-A R1=R2=Ac (CH3CO) MEL-B R1=Ac R2=H MEL-C R1=H

R2=H MEL-D R1=R2=H

Figure 26 General structure of mannosylerythritol lipids (MELs)

62

Similar structure was also reported where Pseudozyma churashimaensis that

separated from sugarcane was used as the producing strain (Morita et al 2011a)

Researchers have studied the properties of MELs of various structures Takahashi

et al investigated the DPPH radical- and superoxide anion- scavenging activities

of MEL-A -B and ndashC indicating that all MEL derivatives exhibited anioxidant

activities although most of them were less effective than arbutin Especially for

MEL-C that secreted by P hubeiensis KM-59 using soybean oil as carbon source

highest DPPH radical scavenging activity of 503 at 10 mg mL-1 and highest

superoxide anion-scavenging activity of 60 at 2 mg mL-1 were showed In

addition to that it has been found that the activity was stronger as increasing the

concentration of MELs and MEL-A with higher unsaturated ratio (557) exhibited

higher activities when compared to MEL-A with that ratio of 412 (Lukic et al

2016) Yamamoto et al applied MEL derivatives on skin that pre-treated with

sodium dodecyl sulfate and found that MELs worked similar as natural ceramide

to recover the viability of skin cells at a high recovery rate of over 80 (Yamamoto

et al 2012) In addition to their moisturising effects on skin Morita et al also found

the healing power of MELs on damaged hair where the cracks on damaged

artificial hairs were repaired by treating with MEL-A and ndashB and the tensile strength

was also increased The inhibition of increase of the average friction coefficient

from 0126plusmn0003 of damaged hair to 0108plusmn0002 when MEL-A was applied and

to 0107plusmn0003 when MEL-B was applied which indicated the ability of MEL

derivatives to smooth hair (Morita et al 2010) Antibacterial capacity of MELs was

studied by Shu and the group where MELs of at a minimum concentration of 0625

mg mL-1 secreted by Pseudozyma aphidis (80 MEL-A dominated) showed

significant inhibitory effects against approximately 80 Gram-positive Bacillus

cereus spores germinated and grew into vegetative cells through disrupting the

formation of cell membrane (Shu et al 2019) It has been demonstrated that this

antibacterial activity against Gram-positive bacteria was affected by the alkyl

chains and pattern of CH3CO group on the mannopyranosyl moiety of MELs

(Nashida et al 2018) More recently MEL-A was evaluated to show antibacterial

activity against another Gram-positive bacteria Listeria monocytogenes that bear

in food indicating their promising application as food preservatives (Liu et al

2020)

63

22522 Production of MELs

Many researches have successfully produced MELs using strains of the genus

Ustilago and Pseudozyma which obtained from rotten fruit (Morita et al 2011b)

factory wastewater (De Andrade et al 2017) and so on Different microorganisms

utilize different carbon sources and synthesize MELs with different structures It

has been found that MELs containing unsaturated fatty acids were greatly

produced when the microorganisms consuming vegetable oil as carbon source

(Lukic et al 2016) Soybean oil sunflower oil and olive oil are reported to be

suitable carbon sources for the cultivation of P rugulosa NRBC 10877 and P

parantarcitica JCM11752 (Yu et al 2015 Morita et al 2013 Recke et al 2013)

Using oily substrates as carbon source normally leads to a higher production of

MELs For example Rau obtained 165 g L-1 MELs by cultivating Paphidis DSM

14930 in the consumption of soybean oil (Rau et al 2005a) However difficulties

are heavily induced for the downstream process of product purification Based on

this some researchers suggested that water-soluble carbon sources such as

glucose glycerol and cane sugar are good alternatives (Faria et al 2014 Yu et

al 2015 Saika et al 2018b Madihalli et al 2020 Kinjo et al 2019) In the

cultivation of Ustilago scitaminea NBRC 32730 in the medium containing

sugarcane juice (224 wt sugars) as sole carbon source Morito reported a yield

of 127 g L-1 MELs in the form of MEL-B (Morita et al 2009b) Also Pseudozyma

Antarctica T-34 was reported to produce MELs when consuming glucose as sole

carbon source (Morita et al 2015) Although the utilization of water-soluble carbon

source for strain cultivation results in relatively lower production of MELs and only

a few strains grow well when consuming water-soluble substrates as single carbon

source it can help reduce the cost and is in favour of downstream purification

22523 Separation and Purification of MELs

Similar as other BSs organic solvent extraction is the most widely used purification

method for MELs isolation where equal volume ethyl acetate is frequently used for

the extraction (Shen et al 2019 De Andrade et al 2017 Wada et al 2020 Shu

et al 2020) followed by a rotary evaporation to get rid of organic solvent or silica

gel column chromatography Solvent extraction method is simple and easy to carry

out But due to large consumption of solvents resulting in higher cost and

contamination to environment development of new technologies for MELs

isolation are uninterrupted Rau et al combined adsorption method with solvent

extraction in the separation of MELs obtaining good separation effect In the study

ion-exchange resin adsorption organic solvent extraction and heating up media

64

broth to 100~121 degC were carried out During the heat treatment MELs transferred

to solid state continually achieving a recovery of MELs of 93 and the purity of

87 (Rau et al 2005b) With only hydrophilic carbon source cassava wastewater

applied in medium cultivating P tsukubaensis for MEL-B production was proposed

by Andrade et al using a novel separation strategy where the overflow was

integrated with ultrafiltration As a result for small scale configuration of 20 mL

centrifugal device 80 of MEL-B was isolated in one step using 100 kDa MWCO

membranes also scaling up to ultrafiltration of 500 mL is feasible where similar

result was obtained (De Andrade et al 2017)

In order to get rid of residual oils and fatty acids in the crude MELs product n-

hexane is typically applied Some studies suggested the usage of chemical

mixtures combing hexane methanol and water in various compositions Rau et al

proposed hexanemethanolwater at a ratio of 163 (pH=55) for lipid removal (Rau

et al 2005b) and recently Shen et al developed an extraction method for oil and

free fatty acids removal using the solvent system containing n-

hexanemethanolwater at a ratio of 121 (pH=2) for MELs extraction as the first

step achieving a recovery of MELs of 80 followed by extraction with solvent

mixture at a ratio of 131 which isolated 14 of MELs and after the last step where

equal volume of n-hexane and methanol was mixed for purification over 90

MELs were extracted (Shen et al 2019) The combination of hexane and methanol

should realize a better removal due to the reason that hexane is non-polar solvent

which is only used for extract lipid of low polarity (neutral lipid) while methanol is

polar solvent which is miscible with medium to high polar lipid

22524 Phase Behaviour of MELs in water

As being synthesized from fatty alcohols and sugars MELs are able to self-

assemble into vesicles self-assembled monolayer sponge phase bicontinuous

cubic phase and three-dimensional ordered lyotropic liquid crystral phase that is

stabled by hydrogen-bond between glycosyl van der waals force and interaction

between molecules (Imura et al 2007) Moreover the thermal stability is

influenced by the chirality of carbon atom The liquid crystal structure endows

MELs with excellent wetting properties It has been reported that presence of multi-

lamellar vesicles facilitated the fusion of MELs and membrane favouring for the

effect of active substance on cell and the enhancement of gene transfection

efficiency (Worakitkanchanakul et al 2008 Coelho et al 2020 Kitamoto et al

2009) Different structures of MELs tend to self-assemble into different structures

65

MEL-A was suggested to form sponge phase (L3 phase) when the concentration

is higher than 1 mM (Imura et al 2007) The structure morphology was interpreted

as coacervates that derived from bilayer structure Besides MEL-A is a natural

compound which can spontaneously form this structure without the aids of other

co-surfactants (Morita et al 2013 Niu et al 2019) In terms of MEL-B and MEL-

C due to the lack of 4rsquo-O-acetyl group or 6rsquo-O-acetyl group causing self-bend

during self-assembling process to change coacervates to vesicles and they can

form vesicles with large diameter over 10 μm (Konishi and Makino 2018 Fan et

al 2018) When the bend curvature becomes zero lamella phase (Lα) is formed

Thus MEL-B and MEL-C can form Lα phase which is stabled by hydrogen-bond

between hydroxyl in C-4rsquo or C-6rsquo (Worakitkanchanakul et al 2009 Fukuoka et al

2011 Fukuoka et al 2012)

The phase behaviour of ternary system of MELs in water has been studied by

Worakitkanchanakul et al where MEL-Awatern-decane and MEL-Bwatern-

decane systems were analysed When using n-decane as oil phase diacetylated

MEL-A formed single phase system namely microemulsion (WO) And MEL-A

formed L3 V2 and Lα phase While monoacetylated MEL-B only formed one phase

and bicontinuous microemulsion (Worakitkanchanakul et al 2009) Noticeably

Lα+oil region of OW emulsion in the system of MEL-Bwatern-decane was easily

to be formed which helped stable emulsion for over a month (Saika et al 2018c

Saika et al 2018b) As the amphiphilic molecules of MELs are different from

traditional ones the study of liquid phase may help reveal the relationship between

MELs structure and its function (Madihalli and Doble 2019 Ohadi et al 2020

Beck et al 2019)

23 Emulsion

Cosmetic creams and emulsions can be used as the skin protector which prevents

skin from the environmental damage such as windy dusty chilly dryness and

humidity and moisturizes the outermost layer of the skin namely stratum corneum

providing oily components to the skin Apart from that emulsions are also good

carriers of active ingredients and drug making them easy to be absorbed by skin

thereby nourishing and regulating the skin (Aswal et al 2013 Banerjee et al

2019)

66

231 Overview of Emulsion

An emulsion is a multiphase colloid system consisting of one or more liquid

dispersing as small droplets in another immiscible liquid Generally emulsions can

be classified as simple emulsions and multiple emulsions where simple emulsion

refers to the system of one liquid dispersing (dispersed phase) as droplets in

another immiscible liquid phase (continuous phase) (Zhu et al 2018) Oil-in-water

emulsions (oil droplets dispersed in continuous water phase) OW and water-in-

oil emulsions (water droplets dispersed in oil phase) WO are two common types

of simple emulsion In comparison the system of multiple emulsions is more

complex where one or more droplets exist in multiple emulsion globule forming

oil-in-water-in-oil (OWO) multiple emulsions or water-in-oil-in-water emulsions

(WOW) (David et al 2019 Bonnin 2019) Microemulsions are isotropic and

thermodynamically stable system with dispersed droplets sizing from 1 to 100 nm

While for macroemulsions with droplet size of larger than 200 nm and

nanoemulsions with that less than 200 nm are thermodynamic instable systems

as the generated two-phase boundary (interface) is large and the energy of the

system is relatively high On account of this emulsifiers are usually added in the

formulation to stable the emulsion system (Patel and Joshi 2012)

232 Emulsion Formation

Emulsions are generally formed through either low- or high- energy technologies

Low-energy method refers to spontaneous emulsification where no external

energy is required and the emulsion system that internally changed in a specific

way under the environment or composition alteration provides stored chemical

energy for itself Researchers proposed transitional inversion where hydrophile-

lipophile balance (HLB) was affected by changing factors such as temperature or

electrolyte concentration and catastrophic inversion methods where volume

fraction of the disperse phase is increased for emulsion preparation (Solans et al

2016 Perazzo et al 2015) However most of accessible surfactants or emulsifiers

are not capable of involving in this type of methods especially those natural

surfactants thus at present high energy emulsification (dispersion) is commonly

applied for commercial use where four main elements are generally required in

the preparation of emulsions water phase oil phase surfactants and energy

(external force) (Cantero del Castillo 2019 Caritaacute et al 2020)

67

2321 Mechanism of high energy emulsification

The change in free energy of emulsification can be expressed according to the

Equation 21 (Leal-Calderon et al 2007)

∆G = ∆Aγ minus T∆S 21

Where T is the temperature ΔS is the change of entropy of dispersion γ is the

interfacial tension between oil and water ΔA is the increase of interfacial area of

oil and water after the formation of emulsion

Generally during the process of emulsification ΔAγ is no smaller than TΔS

namely free energy is always positive If the component in the system is unable to

acquire energy from their own the emulsification process is non-spontaneous

where the energy input is needed Typically mechanical applications such as

homogenizers and mixers are applied for providing energy in order to fragment

dispersed phase into small droplets and intermingle two immiscible phases

Noticeably large energy is needed to generate disruptive forces for overcoming

the Laplace pressure (ΔPL) of the droplets thereby realising fine droplets disruption

(Wang et al 2018b)

∆119875119871 =4120574

11988922

Where ΔPL is the Laplace pressure γ is the interfacial tension between oil and

water d is the droplet diameter

From Laplace equation (Equation 22) when destructive force is higher than

Laplace pressure smaller droplets are obtained In another aspect lowering down

the interfacial tension and maintaining energy input at a certain level can also

produce smaller droplets Thus from this aspect surfactants or emulsifiers involved

in the formulation for emulsification could help facilitate the fragmentation of

dispersed phase into fine droplets through adsorbing onto the droplet surfaces

and reducing the interfacial tension (Lian et al 2019) But this is only worked when

the surfactant adsorbing rate to interface is faster than the droplet disruption rate

for ensuring that the droplets are fully covered by surfactant molecules before they

break down (Agrawal et al 2017) Different types of surfactants or emulsifiers

showing various surface activities help generate droplets in different sizes It has

68

been indicated that biopolymers do not effectively active water and oil interface

(surface tensionasymp15~25 mJ m-2) when compared to small molecular surfactants

(surface tension lt5 mJ m-2) so that they help form larger droplets during mixing

(Zembyla et al 2020 Xie et al 2017 Hantal et al 2019) Another role of

surfactants or emulsifiers play in emulsification is their ability of inhibition of droplet

coalescence for stabilizing the system (Dao et al 2018)

2322 Surfactants in Formulation

Actually instead of using single surface active agent blending of different types of

surfactants in the formulation is more advantageous (Hantal et al 2019 Patil et

al 2015) Mixed emulsifier system containing two or more types of surfactants or

emulsifiers could exhibit better emulsification effect (Vilasau et al 2011b) On the

contrary the interfacial film that formed by highly pure surfactant may not be

closely packed thus the mechanical strength is low It has been found that liquid

paraffin with cholesterol dispersed into sodium hexadecyl sulphate solution will

produce stable oil in water emulsion while only use cholesterol or sodium

hexadecyl sulphase will form an instable one (Ahmadi et al 2020)

Generally mixtures of ionic surfactants and non-ionic surfactants in the formulation

combining both of steric and electrostatic forces could significantly inhibit instability

of the product and present the favourable synergistic effects (Vilasau et al 2011a)

Take Sorbitan esters (Spans) and Polyoxyethylene sorbitol fatty acid esters

(Tweens) mixed surfactant system as an example because the derivative of

polyoxyethylated sorbitol has strong interaction with water phase its hydrophobic

group stretches more into water phase than non-ethoxylated sorbitol thus the

hydrophobic groups of them got closer to each other at the interface Based on this

the interaction between the molecules of two types of surfactants was stronger

than using alone thereby forming an interfacial film with higher strength (Koneva

et al 2017 Posocco et al 2016 Yoo et al 2020) Also the mixed emulsifier

system containing sodium dodecyl sulphate (sodium lauryl sulphateSLS) and

lauryl alcohol can effectively help stable the emulsion (Ade-Browne et al 2020

Morris et al 2019a Penkina et al 2020) In the study of Mandal et al in

comparison with single surfactant-water-oil system the synergistic effect of

combined anionic surfactant (sodium dodecylbenzenesulfonateSDBS) and non-

ionic surfactant (Tween 80) system on the modification of wettability of a reservoir

rock was studied with a ration of SDBSTween 80 at 11 wt And optimal results

69

were obtained from mixed surfactant system showing that the contact angle of

quartz substrate was dramatically decreased with time for realising the complete

alteration of quartz from oil wet to water wet under ambient conditions (Mandal et

al 2016) In the study of surface adsorbed film of surfactant solution polar organic

compounds such as fatty alcohol in the film will greatly increase the surface activity

and the film strength Because fatty alcohols have relatively small hydrophilic head

group (-OH) it can effectively adsorb at the interface and insert into the adsorption

layer of adjacent surfactant molecules thereby causing large surface excess and

low interfacial tension (Falbe 2012) Ibrahim et al studied the formulation of palm

methyl ester-in-water system with different mixed non-ionic surfactants indicating

that the hydrophilic moiety of the non-ionic surfactants affected the stability of

emulsions And an optimal combination of fatty alcohol POE (25 EO) with DLS1

(HLB 11plusmn1) was obtained with highest stability where the stable zeta potential was

ranged from -3791 mV to -408 mV and low surface tension value was

31186~32865 mN m-1 (Ibrahim et al 2015)

Moreover the concentration of surfactants is important for emulsion formation

When adding surfactants or emulsifiers in the system surfactant molecules adsorb

at the interface forming interfacial film which has certain strength This film protects

dispersed droplets to prevent coalescence when crashing into each other

(Marquez et al 2018) Sufficient surfactants in the system namely higher

concentration of surfactants are likely to form interfacial film of strong strength

consisting of tightly arranged surfactant molecules resulting in stronger resistance

to the coalescence of droplets and the emulsion will be formed easily and remain

stable (Kanouni et al 2002) In a study where an emulsion system containing non-

ionic surfactant with oil in water increasing the concentration of surfactant from 2

to 6 led to formation of an emulsion with narrower droplet size distribution

microstructure with enhanced stability (Feng et al 2018) This is also proved by

the theory of composite membrane indicating that only when the molecules of

emulsifier closely aligned to form condensed film can the emulsion be stable

(Poerwadi et al 2020) However the addition of co-emulsifiers may also cause

too high viscosity or even phase separation which directly results in a way too rigid

cream and crystallisation precipitation during the storage (Ballmann and Muumleller

2008) Thus appropriate concentration of surfactants in the formulation is required

Hydrophile-lipophile balance (HLB) is a key factor that affects the choice of

surfactants and the performance of emulsion system especially for its stability

70

Generally more hydrophobic surfactants with HLB value ranging from 3 to 6 are

suitable for emulsifying WO emulsion and OW emulsion is generally prepared

using the HLB value ranged from 8 to 18 (Tadros 2009) Feng et al studied the

effect of different HLB values of surfactants on the polyoxyethylene castor oil ether

(non-ionic surfactant)oil+lambda-cyhalothrinwater (at ratio of 65+584)

emulsion preparation for pesticide appliations It showed that increasing HLB value

of surfactants from 105 to 155 resulted in larger droplets in the system (sized from

044μm to 427μm) and wider droplet distribution thereby resulting in the instability

of the system (Feng et al 2018) However the value of HLB for selected

surfactants andor emulsifiers should be similar to the value that required by the

emulsion system (Hong et al 2018) In another study from Hong et al the effect

of HLB value of a mixed non-ionic surfactant system on the formation and stability

of the OW emulsion was investigated Two mixed surfactant systems MS-01 and

MS-02 respectively containing different concentrations of Span 60ampTween 60 and

Span 80ampTween 80 were studied in the formulation of the emulsion with required

HLB value of 1085 The minimum droplets and highest zeta-potential value

standing for a more stable emulsion system for MS-01 involved emulsion were

observed at HLB=108 and that for MS-02 incorporated emulsion were at

HLB=107 both of the HLB values were close to the required HLB of the system

Also the cream index further provided similar results indicating more stable system

obtained with a HLB value of surfactants similar to the required value of emulsion

system (Hong et al 2018)

2323 Process of Formulation

The preparation of emulsion refers to dispersing one liquid in forms of droplets into

another immiscible liquid Theoretically an emulsion can be formed by simply

mixing two immiscible liquids together and then giving it thoroughly shaking but

the resulted emulsion will be super unstable Thus a more rational method is

suggested as firstly dissolving emulsifiers into the phase in which it is most soluble

following by the adding of another phase Then a high speed mixing or vigorous

agitation is used to shear the mixture (Tadros 2013) Apart from that the addition

sequence of organicaqueous phases and initial location of emulsifiers may also

affect the performance of emulsions Feng et al studied the effect of changing

addition sequence of beta-cypermethrinaqueous phase and different types of

emulsifiers on the nanoemulsions using low-energy emulsifying process finding

that the emulsion prepared by adding aqueous phase into organic phase with

71

emulsifiers exhibited the highest stability compared to other sequences (Feng et

al 2016)

Mixing provides external shear force for the fraction of dispersed phase into small

droplets facilitating formation of emulsions Liquid-liquid mixing is often under

turbulent condition where the interaction between two phases exists (Naeeni and

Pakzad 2019) The turbulent fluctuation in continuous phase facilitates the

breakage of dispersed droplets resulting in the formation of smaller droplets and

big contacting area (Boxall et al 2012) On the contrary dispersed phase has a

damping effect on the turbulence of continuous phase which may reduce its

strength Thus breaking mechanism of dispersed droplets is significant for liquid-

liquid heterogeneous intensive mixing (Theron et al 2010) Research showed that

there were two main factors of droplet breaking in hydraulics 1) viscous shear

stress caused by velocity gradient 2) instant shear stress and local pressure

fluctuation (Reynolds shear stress) caused by turbulence (Liu et al 2010)

Podgorska et al studied the breaking mechanism of silicon oil droplet in a stirred

tank equipped with Rushton agitator and four baffles indicating that droplets

breaking happened mainly around stirring blade due to high system average

energy dissipation rate in this region Besides high viscosity of dispersed phase

helped stabilize droplets in pressure pulse thus having adverse influence on the

deformation and breaking of droplets (Podgoacuterska 2006)

In the system of liquid-liquid dispersion droplets collide followed by coalescence

or separation is based on velocity pulse The collision course can be seen as the

process of film drainage of continuous phase between two droplets and

coalescence time and contact time of droplets determine whether collided droplets

merge immediately or separate apart Namely two droplets will coalesce when the

contact time is longer than coalescence time In the study of modelling droplets

coalescence in liquid-liquid dispersions in flow through fibrous media where a

model formulation named coalescence efficiency was used in order to estimate the

tangible effect of coalescence a simplified model of Coulaloglou was applied

(Krasinski 2013)

120578119888119900119886119897 = exp (minus119905119889

119905119888) 23

Where td is the drainage time (referred to coalescence time) tc is the contact time

The coalescence time is required for thinning the film between two droplets to a

72

certain value (critical thickness) Ban et al studied the coalescence behaviour of

the system with methylbenzene droplets in water suggesting that concentration of

acetone in methylbenzene direction of mass transfer contact time of droplets and

flow velocity of continuous phase have influence on the coalescence of

methylbenzene droplets Among them the concentration of acetone and direction

of mass transfer determined the duration of coalescence time When acetone

transferred from dispersed phase to continuous phase average coalescence time

decreased with the concentration of acetone increases in the opposite direction

the coalescence of droplet was easily be blocked (Ban et al 2000)

During the mixing process droplet coalescence and breakage is in a dynamic

equilibrium The minimum stable droplet size dmin is a judgement for whether

droplets coalesce or not When droplet size is smaller than dmin droplets are

instability and easily coalesce According to the analysis of isotropic turbulent

dispersed system Liu proposed a model for calculating dmin (Liu and Li 1999)

119889119898119894119899311 =

120574138119861046

00272120583119888120588119888084휀089

24

Where dmin is the minimum stable droplet size γ is the interfacial tension B is the

van der Waals constant μc is the viscosity of continuous phase ρc is the density

of continuous phase ε is the energy dissipation The equation directly reflects the

relationship between minimum droplet diameter and physical properties of system

In order to achieve homogeneously mixed products the mixing equipment should

allow the fluid system either flow entirely to avoid any stagnation area or under

high shear or high flow mixing to break the inhomogeneity (Gao et al 2016)

Mechanical devices that wildly used for mixing are mixing stirrers colloid mills

homogenizers and ultrasound generators Mixing stirrers are generally divided into

high speed stirrers and low speed ones which refers to agitating liquid under a

turbulent flow and viscous flow respectively (Vikhansky 2020) The former ones

(such as blade propeller and turbine type) are applicable for mixing low viscous

liquid and the latter ones (such as anchor) are normally used for high viscous and

non-Newtonian fluid (Uhl 2012) Homogenizers consist of a rotor-stator system

creating shearing behaviour between the gap of rotor and stator which is usually

applied for liquid emulsification and solid-liquid material crush dispersing and

mixing (Castellano et al 2019 Farzad et al 2018)

73

Some parameters should also be taken into account for cream preparation such

as emulsification temperature time and the agitation speed Generally the

temperature of oil and liquid phase should be controlled between 75˚C and 85˚C

for semi-solids production During the cooling stage although higher cooling rates

will generate smaller droplets too high cooling rate may also lead to materials with

high melting point or low solubility crystalize thereby bringing poor emulsification

effect (Moens et al 2019) For the same system and dispersion method the

droplets size will decrease as increasing the emulsification time But it will reach

an equilibrium that is to say when the droplets become small enough further

emulsification will not change its size Thus the emulsification time should be

controlled to a rational value in case of meaningless economic loss (Pivsa-Art et

al 2019) The agitating speed also has significant effects on the emulsification

Too fast speed will entrap air into the system which tends to make the emulsion

unstable Thus as a general rule higher speed agitating is helpful at the beginning

of emulsification when the process enters cooling stage medium or lower speed

of mixing is preferred for the purpose of minimize the trapping of air (Colafemmina

et al 2020a Chizawa et al 2019 Santos et al 2016)

233 Mechanisms of Emulsion Instability

As mentioned above the emulsification process is generally non-spontaneous In

the opposite when the droplets coalesce interfacial area of system will decrease

namely the free energy of system (G) decreases This is a spontaneous process

Therefore emulsion system is thermodynamic instable where the

physicochemical properties will change with time Four phenomena of emulsion

instability have been reported coalescence flocculation creaming and breaking

which are illustrated in figure 27 (Khan et al 2011)

Flocculation is a process where two or more small emulsion droplets associate

together to form large aggregates which is reversible because each droplet still

remains its individual integrity Some researchers made a statement that the

reason for this process is due to the depletion effect when excess surfactant exists

in the continuous phase of an emulsion system (Huck-Iriart et al 2016) In detail

excess surfactant will form micelles flowing around in the bulk liquid If two droplets

are very close to each other (droplets distance smaller than the diameter of the

micelles) there may be low concentration of micelles in the inter space between

two droplets (Koroleva et al 2015) As a result the osmotic pressure difference

74

drives micelles flow out of the gap between the droplets and induces the

aggregation of them (Dickinson 2019)

Creaming phenomenon is happened when the dispersed phase separates and

then forms a layer upon the continuous phase Christopher and Dawn pointed out

that the increase of the viscosity of continuous phase will help inhibit this

phenomenon which is also proved by Stokersquos law (Langley and Belcher 2012)

V =1198632(120588119878 minus 120588119874)119892

1812057825

Where V is the creaming rate D is the diameter of dispersed droplets ρs is the

density of dispersed phase ρ o is the density of continuous phase η is the

continuous phase viscosity and g is gravitational acceleration (Shinoda and

Uchimura 2018) Over time when the droplets merged together to form a large

droplet a new process occurred which is known as coalescence followed by the

breaking of emulsions (Trujillo-Cayado et al 2016) Factors that influence the

stability of emulsions normally can be divided into two aspects internal factors and

external factors The internal factors include the interfacial tension the intensive of

interfacial film effect of interfacial charge droplet size distribution and phase

volume ratio and so on (Marquez et al 2018 Neumann et al 2018 Sun et al

2017) As for external factors mixing temperature mixing speed and time will affect

the stability of emulsion (Wang et al 2018a)

Good emulsion

Coalescence Flocculation

Creaming Breaking

Figure 27 Instability phenomena of emulsions

75

24 Rheology

Flow properties of cosmetic materials directly associate with the quality of final

products and peoplersquos preference which could be characterised with the help of

rheology (Colo et al 2004) Cream products applied by consumers for end-use

undergo sampling rubbing to after-feeling Sampling refers to the process when

consumer taking the cream out from the container with the fingertip where

appropriate thickness and consistency of the cream is expected The physical and

chemical parameters related to this stage are hardness cohesiveness springiness

and adhesiveness During rubbing the cream is expected to exhibit good

spreadability and absorbency After spreading the cream on the skin the

consistency of cream without any granular sensation is expected after which

appropriate amount of greasy leftovers on the skin are also key factors determining

customersrsquo satisfaction (Moravkova and Stern 2011)

241 Rheology of Emulsions

Some cosmetic products such as toothpastes lipsticks foundations anhydrous

cream parts of emulsions are plastic fluids When the system is at rest particles

form three-dimensional space structure (Brummer 2013) The existence of yield

value is due to the strong three-dimensional space force which makes the system

possess the property of the solid-like and have relatively high viscosity during low

shear range Once the extra shear stress surpasses this critical value the structure

will be collapsed and then fluid begins to flow When this external stress is

removed the structure of the system will gradually recover to some extent (Akbari

and Nour 2018) In real practice semi-solid creams show both viscosity and

elasticity responses to external force thus these substances are known as

viscoelastic materials (Tschoegl 2012) In this type of fluid system after the

external force is removed part of deformation energy is used to return to its original

state and part of that is converted to heat and lost thereby performing like both

viscous liquid and elastic solid

Most cosmetic emulsions and creams possess sophisticated shear related and

time related flow characteristics Thus from the blending process to filling process

then until any time during consumers use the viscosity of the cosmetic changes

with applied shear rate or stress Table 25 presents typical shear rate ranges of

emulsions and creams occurring in different industrial applications (Mezger 2020)

76

Table 25 Typical shear rate ranges of emulsions and creams during different industrial applications adapted from Mezger 2020

However Sherman suggested that when consumers dispensed and rubbed

creams on hand or face the shear rate is in a certain range (Sherman 1968) The

choice of the measurement range of rheological behaviour aims to provide the

information of properties that related to the product at rest or during the usage of

consumers (Salehiyan et al 2018) Applying the Equation 26 which defines the

shear rate ṙ along with some assumptions specific shear rate values for different

processes are calculated by Langenbucher et al (Langenbucher and Lange 1970)

ṙ =V

h26

Where V refers to the speed of rubbing by hand h refers to the thickness of cream

layer on skin surface Table 26 shows calculation values of shear rate occurring

in different applications of creams under certain assumptions (Langenbucher and

Lange 1970)

Table 26 Theoretical values of shear rate related to different processes of cream application adapted from Langenbucher and Lange 1970

Process Assumptions in

calculation

Calculation

values of shear

rate

ṙ (s-1)

Taking cream from the jar Layer thickness 2cm

Velocity 2cms

1

Rubbing on

the skin

Layer thickness 02cm

Velocity of dispensing and

extending 24 cms

120

primary stage Layer thickness 01cm


extending 10 cms

100

intermediate stage Layer thickness 001cm


extending 10 cms

103

ending stage Layer thickness 0001cm


extending 10 cms

104

Process Shear rate range ṙ (s-1)

Sedimentation of particles 10-6 to 10-3

Mixing or stirring 10 to 104

Rubbing the cream on the skin 103 to 105

77

242 Rheometry and Rheometers

Rheometry is the technology which is used to measure rheological behaviour of

the flow and determine the corresponding rheological data with the help of a

rheometer where the flow phenomena are studied allowing the materials subject

to various external forces (Coussot 2005 Salehiyan et al 2018) Typically two

main measurements are normally carried out to investigate flow properties steady

state test and dynamic oscillatory test The steady state tests are non-linear which

is used to characterize the viscous behaviour Within a range of shear stresses

and shear rates the viscosity is measured as a function of the imposed parameters

(Malkin 2013) There are two modes in rotational tests tests with controlled shear

rate (CSR) that usually applied for the investigation of liquid presenting self-

levelling behaviour and tests with controlled shear stress (CSS) where the shear

stress or torque is pre-set and controlled by the rheometer (Zhao et al 2013 Li et

al 2012) CSS method is generally used to determine yield points of dispersions

or gels and more viable for determining rheological behaviours of non-Newtonian

flows especially with semi-solid properties compared to CSR (Coussot 2005

Kukla et al 2016 Ahmed 2019)

Dynamic oscillatory test refers to adding oscillatory stress or stain to the

viscoelastic materials to measure the generated shear strain that related to time

Generally a function of frequency or time will be measured including measuring

parameters such as storage and loss moduli (Grsquo and Grsquorsquo) phase lag complex

modulus (G) and viscosity (η) These properties are normally confined to a

specific range of strains or stresses where no visually movement of the material is

observed This range is known as linear viscoelastic range where the storage and

loss moduli are independent with oscillatory strain or stress (Pan et al 2018

Kaspchak et al 2017 Sanz et al 2017 Zhang et al 2019a)

Rheological studies were carried out in order to understand flow properties and

viscosity profiles of emulsions and surfactant solutions that applied in emulsion

formulation The rheological behaviour of systems where cetyltrimethylammonium

chloride (CTAC) behenyltrimethylammonium chloride (BTAC)

CTAChydroxyethyl cellulose (HEC) respectively mixed with fatty alcohols (FAs)

were studied showing that higher concentration of FA increased the storage

moduli the yield stresses and the zero-shear-rate viscosity in CTACFA and

BTACFA emulsions (Nakarapanich et al 2001) This behaviour was also

investigated by Ade-Browne et al where the increase the amount of lauryl alcohol

78

in sodium lauryl sulfate with different degrees of ethoxylation enhanced the system

viscosity and the formation of a gel (Ade-Browne et al 2020) Similar higher

concentration of an individual alcohol cetyl alcohol in the system of sodium

dodecyl sulfate (SDS) facilitated the formation of stronger gel with higher storage

modulus (Grewe et al 2015) The mechanisms of solubility limits of fatty alcohols

(FAs) in sodium laureth sulfate (SLES)cocoamidopropyl betaine (CAPB) mixed

micellar solutions were studied indicating that the solubility limits were positively

associated with the surfactant concentration and negatively related to the alcohol

chain length (Tzocheva et al 2015) Mitrinova et al studied rheological impacts of

co-surfactants of various structures on mixed surfactant solutions containing

sodium laureth sulfate (SLES) and zwitterionic cocoamidopropyl betaine (CAPB)

They revealed that viscoelasticity of SLESCAPB system was affected by the

chain-length and head-group size of cosurfactants In addition to that the head-

group charge gave priority to govern this behaviour (Mitrinova et al 2018)

Rheological behaviour of mixed surfactant solutions of sulfonated methyl esters

(SME) and cocamidopropyl betaine (CAPB) were also investigated which

exhibited a higher viscosity compared to the system containing sodium dodecyl

sulfate (SDS) and CAPB It also showed that further addition of the fatty alcohol

1-Dodecanol exceeding their concentration limit led to the decrease in viscosity

and precipitation was witnessed due to giant micelles transforming into drops or

crystallites However the addition of the non-ionic surfactant cocamide

monoethanolamine (CMEA) as thickener only promoted the growth of micelle and

increase of system without causing precipitation (Yavrukova et al 2020) CMEA-

SLES binary mixtures were investigated by Pandya et al revealing that CMEA

solubilized in SLES solution facilitated the micellar transition from sphere-like to

rod-like and the increase in viscosity (Pandya et al 2020) Some studies also

investigated systems that stabilised by biosurfactants A concentrated emulsion

containing 50 wt oil that emulsified by rhamnolipids were formulated in the study

of Li et al and shear-thinning behaviour and low consistency coefficient of the

emulsion were determined (Li et al 2018) In addition to that ternary system of

sodium laureth sulfate (SLES) zwitterionic cocamidopropyl etaine

(CAPB)rhamnolipids (monodirhamnolipids mixture) was characterised with the

help of rheology It was found that the addition of rhamnolipids biosurfactant on

SLESCAPB system led to a decrease in viscosity providing rheological

understanding of surfactantsbiosurfactants ternary system for bio-based product

formulation (Xu and Amin 2019)

79

In order to obtain relatively accurate rheological result different measuring

systems are used based on the natures of materials The most common measuring

systems are concentric cylinder measuring system cone and plate system and

parallel plate system (Song et al 2017) In the rheological measurements for a

cream system containing water oil and sorbitan monoester as surfactant a

rheometer equipped with a concentric cylinder system (diameter of 15 mm) was

applied The LVR was obtained using the oscillatory stress sweep at the constant

frequency of 1Hz where the oscillatory stress increased from 006 to 100 Pa The

end point of LVR was determined in terms of oscillatory stress when the storage

modulus value was decreased by 10 from the linear plateau After that a value

within LVR was selected using in a creep recovery test where the sample was

imposed the stress for 120 s and then the recovery was set to 360 s As a result

the creep compliance J changed depending on time was obtained This can also

be used to indicate the elastic and viscous structure of the cream (Korhonen et al

2002)

When using cone and plate geometry much less sample is required than using

concentric cylinder Normally the angle between the surface of the cone and the

plate is of the order of 1deg and the cone is rotated and the force on the cone is

measured (Maazouz 2020) This type of measuring system is more suitable to

measure samples with medium and high viscosity (Kulik and Boiko 2018) In order

to study the influence of different polymers in an OW emulsion Gilbert et al

applied rheological measurements in the study where the flow properties of natural

natural modified and chemically synthetic polymers of 1 wt that respectively

formulated in an emulsion were tested Continuous flow test was conducted using

a rheometer equipped with cone-plate geometry (an angle of almost 1deg diameter

of 40 mm) The gap between cone and plate was set to be 27 μm The viscosity

was recorded under the imposed shear rate ranging from 001 to 1000 S-1 for 150

s From the result it was obtained that all the emulsions showed shear thinning

behaviour Also three emulsions exhibited a yield stress (Gilbert et al 2013)

During the viscoelastic properties study oscillatory measurements were carried

out using a cone and plate with an angle of 4deg (diameter of 40mm) and the gap

was changed to 130 μm An oscillatory strain sweep was conducted from the strain

ranging from 001 to 100 at the frequency of 1 rad s-1 to obtain the linear

viscoelastic region (LVR) Besides a time sweep and a creep-recovery test were

also carried out to characterize the viscoelastic properties of each emulsion with

different polymers (Gilbert et al 2013) Another study was conducted rheological

80

measurement on cosmetic emulsions using rheometer equipped with a cone and

plate sensor system (2deg for measuring body lotions and facial creams 1deg for sun

lotions and eye creams) Through carrying out a steady state shear with shear rate

increasing from 0 to 600 S-1 the fluid type of each cosmetic emulsion was obtained

Also the yield stress was obtained for some types of emulsions By comparing the

rheological analysis and sensory assessment the former was proved to be more

applicable in the evaluation of stability of cosmetic emulsions (Moravkova and

Stern 2011)

However the cone and plate measuring system is not applicable to measure

dispersion system with large particles as the particles in the cone angle area are

needed to be forced out to contact with cone plate The normal forced is required

to measure the radicle flow of sample in the gap If the sample has very high yield

stress the radicle squeezing flow will be hindered Sometimes radicle secondary

flow will happen which has the opposite effect on the annular main flow This can

influence the laminar condition of main flow (Moravkova and Stern 2011) Thus

parallel plate measuring system seems to be a good substitute for cone and plate

one which uses an upper plate to replace the cone plate This design avoids the

problem of radicle secondary flow thus it is suitable to measure materials with

large particles (Mezger 2006) However if the viscosity of measured material

greatly depend on shear rate the constant shear rate cannot be obtained under

the given spinner speed Thus the results from parallel-plates measurement are

required to be corrected using Weissenberg-Rabinowitsch corrections (Stan et al

2017 Morillas and de Vicente 2019) Another study of the application condition of

cream and lotion was conducted using a rheometer equipped with parallel plate

system (diameter of 25 mm gap of 2 mm) The steady state shear test was carried

out at the temperature of 35 ˚C with the shear rate ranging from 001 to 625 S-1

As a result yield stress was witnessed and the value of cream was 10 times

greater than that of lotion In addition both of cream and lotion showed shear

thinning behaviour In the oscillatory tests oscillatory frequency sweep tests within

angular frequencies range from 0025 to 100 rad s-1 was performed on the cream

and lotion under a constant strain of 1 and 02 respectively The result also

showed that both for both of cream and lotion the storage modulus was over loss

modulus through the whole measuring range indicating elastic behaviour was

predominant within small amplitude (Kwak et al 2015)

81

Chapter 3 Materials and Methodology

This chapter summarised experimental work involved in this project where

theories and experimental procedures will be introduced It is classified into three

sections bio-surfactant production cream formulation and characterisation

methods

31 Sophorolipids (SLs) Production

The production of SLs in this work is referenced from the study of Ben et al

(Dolman et al 2017) in our group including selection of producing microorganisms

media preparation and strain cultivation strategy

311 Producing Microorganisms

The yeast Candida Bombicola ATCC-22214 was selected as the producer strain

for SLs production in this project and the working stock was stored in cell vials at

-80 degC

312 Chemicals

Chemicals and organic solvents that used for the media broth preparation and

product purification including yeast extract peptone and monohydrate glucose

were obtained from Sigma Aldrich (UK) and Crisp ~N Dry oil providing rapeseed

oil that was obtained from Tesco For purification of bio-surfactant product ethyl

acetate and n-Hexane (Sigma Aldrich UK) were applied

313 Production Strategies

3131 Fermentation Technology

In order to obtain single colony of cell Candida bombicola from working stock was

firstly inoculated to the agar plate from cell vial followed by cultivation for 48 h at

25 degC Shake flask fermentation was used for SLs production In order to produce

a high cell concentration and keep cell viability and peak cells at the same growth

stage a pre-cultivation was carried out before the shake flask fermentation 10

(vv) inoculum from pre-culture was added into fermentation media (Dolman et al

2019)

The composition of pre-culture media is the same as that of fermentation culture

which contained yeast extract of 6 g L-1 peptone of 5 g L-1 glucose of 100 g L-1

and Crisp ~N Dry oil of 100 g L-1 250 mL Erlenmeyer shake flask containing 25

82

mL media and 500 mL Erlenmeyer shake flask containing 50 mL media were

respectively prepared for pre-cultivation and shake flaks fermentation (Dolman et

al 2019)

Except oil and glucose the other ingredients were firstly added into the shake flask

and prepared according to the composition as mentioned above Then they were

sterilized via autoclave along with oil separately and other auxiliary glassware

The glucose was filtered with 02 nm membrane to get sterilization

After 48 hours of cultivation in agar plate single colonies were inoculated to the

pre-culture shake flask followed by incubation for 30 h at 25 degC with a rotating

speed of 200 rpm Then the optical density (OD) of cells was measured using

spectrophotometer with the wavelength of 600 nm The value of that could be taken

as a representative to immediately measure cell concentration thereby

determining the percentage of pre-culture that used for further inoculation As the

OD value of 20 was needed in this experiment the pre-culture media was mixed

with supplementary culture media containing only 6 g L-1 peptone and 5 g L-1 yeast

extract Subsequently 10 (vv) of the mixture with OD value of 20 was inoculated

into fermentation culture in 500 mL Erlenmeyer shake flask stored in the incubator

for 8 days at 25 degC with the same shaking speed as pre-culture incubation All

inoculation procedures were carried out under aseptic condition (Dolman et al

2019)

3132 Isolation and Purification

31321 Chemicals and Solvents

Solvent extraction was carried out for SLs isolation and purification where ethyl

acetate (VWR UK) and n-hexane (Fisher Scientific UK) were used

31322 Experimental Procedure

Equal volume of n-hexane to culture media was firstly added into broth in order to

remove residual oil thus the oil was extracted with the solvent in the supernatant

After washing the broth with n-hexane twice and pipetting out the supernatant SLs

was isolated by adding equal volume of ethyl acetate to the rest media broth

(Dolman et al 2017) The solvent phase consisting of ethyl acetate and SLs was

separated from the broth by gravimetric method with the help of separating funnel

In order to get rid of ethyl acetate and achieve purified SLs product this solvent

phase was evaporated using rotary evaporator Extracted SLs was stored in a

bottle and kept in the fridge at around 4 degC for further analysis

83

3133 SLs Concentration Determination

31331 Gravimetric Method

Ethyl acetate (VWR UK) and n-hexane (Fisher Scientific UK) were applied in the

concentration determination on SLs using gravimetric method

Gravimetric method for SLs concentration determination was carried out right after

the fermentation 3 mL media broth was pipetted into centrifuge tubes Equal

volume of n-Hexane (3mL) was twice added into the broth to extract the residual

oil presenting in the upper layer After removing this supernatant media broth that

left in the tube was mixed with equal volume of ethyl acetate With the help of

vortex to achieve a well mixing and complete extraction glycolipids were fully

dissolved in ethyl acetate in the supernatant Then this supernatant was poured

into pre-weighed drying dishes denoted as W10 After being left in the fume

cupboard for 24 h the solvent was fully evaporated and the dish was weighed and

denoted as W1 Thus the concentration of glycolipids can be estimated using

Equation 31

1198821 minus 11988210

119881times 100 31

Where W1 is the dish and dried SLs W10 is pre-weighed dish V is the media broth

31332 Exploratory Measurement with high performance

liquid chromatography (HPLC)

Acetonitrile in HPLC grade for gradient analysis (Fisher Scientific UK) and water

in HPLC grade (Fisher Scientific UK) were used in the measurement

High performance liquid chromatography (HPLC) for SLs concentration analysis

was preliminary carried out with the help of UltiMate 3000 instrument equipped

with a UV detector C18 column was selected as the analytical column

Sample for the measurement was prepared by scooping a quarter spoon amount

of extracted SLs (nearly 50 mg) using a Nickel Dual SpoonSpatula utensil (Fisher

Scientific UK) and fully dissolving in 20 (vv) acetonitrile solvent The mixture

was then filtered through a 022 microm membrane and stored in HPLC sample vials

(Dolman et al 2017) Five bottles were prepared of the measurement

The parameters for the measurement were pre-set and displayed in Table 31

(Dolman et al 2017) 20 microl sample solution was injected into HPLC and then

being measured according to the settings

84


(Dolman et al 2017)

32 Mannosylerythritol Lipids (MELs) Production


Pseudozyma aphidis DSM 70725 was selected as the producing strain for MELs

production As train was freshly purchased working stock was prepared prior to

the experiment The purchased strain was streaked onto an agar plate containing

30 g L-1 glucose 1 g L-1 NH4NO3 03 g L-1 KH2PO4 and 1 g L-1 yeast extract then

grown for 2 days at 30 degC (Dolman et al 2019) Single colonies were inoculated

from agar plate to 50 mL cultivation media followed by incubation for 30 h at 30 degC

with the rotating speed of 200 rpm The media broth was centrifuged after which

sterile media was added to replace the supernatant After few times of this

refreshment 15 mL of 30 glycerol 3 mL of 30 g L-1 glucose and media was mixed

together and added up to 50 mL 1 mL of the mixture was aseptically transferred

into each cryovial using sterile pipette tips and stored at -80 degC as working stock

for further use

322 Chemicals

Chemicals that used for MELs production included monohydrate glucose

Ammonium Nitrate (NH4NO3) Monopotassium Phosphate (KH2PO4) yeast extract

Sodium Nitrate (NaNO3) Magnesium Sulfate Heptahydrate (MgSO4middot7H2O) and

Crisp ~N Dry oil Except Crisp ~N Dry oil as the rapeseed oil source which was

purchased form supermarket other chemicals were obtained from Sigma Aldrich

The purification of MELs was also performed using solvent ethyl acetate and n-

Hexane

Parameters Input

Elution Method Gradient

Mobile Phase Acetonitrile-Water

Elution Procedure Concentration of acetonitrile was increased from

20 to 70

Elution Duration (min) 75

Flow Rate (mL min-1) 1

Wavelength of UV

Detector

207

85



Shake flask fermentation was initially carried out for the production of MELs which

was partially adapted from the strategy applied for SLs production (Dolman et al

2019) The strain was inoculated from stock culture to agar plate for cultivation of

2 days at 30 degC Single colonies were transferred and incubated in 250 mL

containing 25 mL pre-culture media (seed culture) [30 g L-1 glucose 1 g L-1 NH4NO3

03 g L-1 KH2PO4 1 g L-1 yeast extract] at 30 degC under rotating of 200 rpm After 2

days of incubation in pre-culture the optical density of cells was measured to get

a preliminary understanding of the growth condition After diluting the cell

concentration to OD value of 20 10 (vv) of seed culture was sterilely added into

500 mL Erlenmeyer flask containing 50mL culture media [30 g L-1 glucose 72 g L-

1 rapeseed oil 2 g L-1 NaNO3 02 g L-1 KH2PO4 02 g L-1 MgSO4middot7 H2O 1 g L-1

yeast extract] followed by the cultivation of 10 days at 30 degC in the incubator with

a shaker rotating at 200 rpm

Fed-batch fermentation was performed afterwards aiming to achieve higher

production of MELs In Fed-batch culture concentrated media containing 500 g L-

1 glucose 28 g L-1 NaNO3 24 g L-1 yeast extract was added into each experimental

Erlenmeyer flask as well as the Crisp ~N Dry oil offered rapeseed oil According

to the analysis of pre-culture maximum consumption rate of glucose NaNO3 and

yeast extract by Rau L et al (Rau et al 2005b) the feeding rate of concentrated

medium was set as 01 mL h-1 and that of oil was set as 002 mL h-1 They were

added into the culture media after 4 days of cultivation



Ethyl acetate (VWR UK) n-hexane (Fisher Scientific UK) and methanol in

analytical grade (Fisher Scientific UK) were used during this procedure


Solvent extraction was also applied for MELs purification After 10 days of batch

cultivation and 20 days of fed-batch cultivation the culture broth was mixed with

an equal volume of ethyl acetate to extract MELs where the upper organic phase

was separated Vacuum rotary evaporator was then applied to get rid of solvent

and then the sticky crude MELs product was obtained Three-time wash of the

86

crude MELs was carried out using the solvent of Hexane-methanol-water (163)

mixture where two separated phases were obtained one is the upper organic

phase containing oil and fatty acid the other is the aqueous phase containing

MELs After that the aqueous layer was washed with hexane twice and the solvent

was then evaporated followed by a freeze drying to get rid of water

33 Preliminary Trials on Cream Formulation

At very first beginning creams were formulated to investigate a feasible recipe and

proper mixing apparatus thus this chapter conclude the exploratory experiments

for cream formulation The recipe was preliminary created based on E45 cream

where only active ingredients and some specified surfactants were applied And

the weight concentration for each component was determined based on a nigh

cream formula from a formulation book (Flick 2001)

331 First Trial for Formulation of Cream without Sodium

Lauryl Ether Sulfate (SLES) Using a Homogenizer

3311 Chemicals

A trial cream was preliminary prepared where light liquid paraffin (Scientific

Laboratory Supplies) white soft paraffin (Fisher Scientific) 1-Hexadecanol (Cetyl

AlcoholCA) (95 Sigma-Aldrich) and deionized water were applied in the

formulation

3312 Recipes

400 g of mimic cream was formulated where only cetyl alcohol was applied as the

emulsifying agent in the formulation Details of the composition is introduced in

Table 32

Table 32 Formulation of first trial cream with cetyl alcohol as sole emulsifying agent

Ingredients Weight Concentration

(wt)

Mass

(g)

Oil Phase (A)

White soft paraffin

Light liquid paraffin

Cetyl alcohol

145

126

12

58

504

48

Aqueous Phase (B)

Deionized water

609

2346

Fragrance and preservatives NA

87

3313 Apparatus and Configurations

A homogenizer (IKA T25 Ultra Turrax Homogenizer IKA England LTD) was

applied for preparing cream at the first trial equipped with a PYREX beaker of 500

mL as the mixing vessel A stir and heater was used as the heating source for the

mixing

3314 Formulation procedure

Cream was prepared following the procedure introduced below

1 White soft paraffin liquid paraffin and CA were weighed separately using

an electronic scale followed by mixing together in a laboratory beaker and

heating up to 70 degC with the help of a stir and heater Then the beaker

containing oil phase mixture was kept in a water bath for keeping

temperature constant

2 Specific amount of deionized water was measured using a cylinder and

then added into the mixing beaker While being heated to reach 70 degC by

the heater water was also being stirred using homogenizer at lower speed

3 Oil phase was slowly poured into aqueous phase while mixing at 8000 rpm

using the homogenizer and temperature was controlled at 70 degC

4 Leave the mixture of oil phase and aqueous phase to be mixed for 10

minutes Regularly check the temperature to maintain it at 70 degC

5 After 10 min of mixing the heater and stirrer was powered off The cream

was cooled down for 10 min and reached room temperature (25plusmn2 degC) by

immersing the mixing beaker in another plastic container filled with tap

water

332 Second Trial for Formulation of Cream with Sodium

Lauryl Ether Sulfate (SLES) Using an overhead stirrer

For the second trial sodium lauryl ether sulfate (SLES) was added into the formula

and an overhead stirrer was applied instead of the homogenizer for mixing

3321 Chemicals

Light liquid paraffin (Scientific Laboratory Supplies) white soft paraffin (Fisher

Scientific) 1-Hexadecanol (Cetyl AlcoholCA) (95 Sigma-Aldrich) Sodium

Laureth Sulfate (SLES) (Scientific Laboratory Supplies) and deionized water were

applied in the formulation

88

3322 Recipes

400g of mimic cream was formulated where CA and SLES were applied as mixed

emulsifying agents in the formulation Details of the composition is introduced in

Table 33

Table 33 Formulation of second trial cream with cetyl alcohol and SLES as mixed emulsifying system


A modification in the configuration of formulation was made in the second trial of

cream preparation An overhead stirrer (IKA Overhead Stirrer RW 20 digital IKA

England LTD) equipped with a pitched 6-blade impeller which was an agitator

providing axial flow was introduced to replace the homogenizer

As sketched in Figure 31 along with the photo of overhead stirrer this simplified

configuration consisted of a 500 mL beaker (PYREX USA) that used as the mixing

vessel an overhead stirrer and a heater (IKA Magnetic Stirrer C-MAG HS 7 IKA

England LTD)


(wt)

Mass

(g)

Oil Phase (A)

White soft paraffin


Cetyl alcohol

145

126

6

58

504

24

Aqueous Phase (B)

Deionized water

SLES

609

2346

6 24

Fragrance and preservatives

NA

89



1 Oil phase components including white soft paraffin liquid paraffin and CA

were weighed separately using an electronic scale followed by mixing

together in a laboratory beaker and heating up to 70 degC with the help of a

stir and heater Then the beaker containing oil phase mixture was kept in a

water bath for keeping temperature constant

2 Aqueous phase consisted of SLES and water SLES was weighed using

electronic scale Specific amount of deionized water was then measured

using a cylinder and added into the mixing beaker The mixture was heated

up to 70 degC while mixing using the agitator at lower mixing speed (200 rpm)

3 Oil phase was slowly poured into aqueous phase followed by being mixed

at 500 rpm for 10 min and temperature was controlled at 70 degC Regularly

check the temperature to maintain it at 70plusmn2 degC




water

Oil

phase

Aqueous

phase


90

34 Modified and Standard Experimental Procedure for

Cream Formulation

Based on the previous trials for cream formulation the standard formulation

system was established where the selection of emulsifying system the

composition and preparation process were determined This chapter will introduce

the modified cream formulation process where creams were formulated in lab

scale with different emulsifying systems consisting of various concentration of

surfactant components In this thesis those formulated using chemically

synthesized surfactants are named mimic creams and those involved bio-

surfactant are bio-creams

341 Chemicals

Ingredients applied in the formulation included light liquid paraffin (Scientific

Laboratory Supplies) white soft paraffin (Fisher Scientific) Groovy Food Organic

Extra Virgin Coconut Oil Stork Original Baking Block (containing 75 vegetable

oils) 1-Hexadecanol (Cetyl AlcoholCA) (95 Sigma-Aldrich) Glycerol

Monostearate (GM) (purified Alfa Aesar) Sodium Laureth Sulfate (SLES)

(Scientific Laboratory Supplies) biosurfactants (SLs and MELs that produced in

lab) deionized water As summarised in Table 34 these ingredients are classified

into different groups according to roles that they played in the formulation

Table 34 Classification of ingredients in the cream formulation

Phases Components

Oils Mixed paraffin oils Light liquid paraffin mixed with white soft paraffin

Bio-oils Groovy Food Organic Extra Virgin Coconut Oil Stork Original Baking

Block

Emulsifying system

Chemical surfactants

Sodium laureth sulfate 1-Hexadecanol (cetyl alcohol) glycerol

monostearate

Biosurfactants Sophorolipids mannosylerythritol lipids

Water Deionized water

342 Recipes

3421 Formulation_Ⅰ

The selection of oil and surfactants and the determination of oil concentration was

referenced from the recipe of E45 cream In order to formulate a mimic cream

91

exhibiting similar performance to the E45 recipes were created with different

surfactant compositions in the emulsifying system This began with the formulation

of a night cream in Flickrsquos book (Flick 2001) after which a few groups of

emulsifying systems were applied in the formulation These mimic creams were

prepared in Formulation_Ⅰ details of which is presented in Table 35

Based on different compositions of fatty alcohols (cetyl alcohol and glycerol

monostearate) 16 creams 50 g of each were prepared and classified into four

groups denoted as F1 F2 F3 and F4 where different concentrations of sodium

laureth sulfate (SLES) were involved An assumption was made that 5 wt of

residuals were not applied in the Formulation_Ⅰ such as fragrances and

preservatives


surfactant system

3421 Formulation_Ⅱ

In order to further investigate the effect varied concentrations of fatty alcohols on

the performance of creams Formulation_Ⅱ was prepared where two groups of

creams were formulated with different concentrations of CA in two emulsifying

systems containing different concentration of SLES denoted as F5 and F6

Mimic Creams

Ingredients F1 F2 F3 F4

Component (wt)

White soft paraffin

145 145 145 145


126 126 126 126

SLES 0 2 4 6 0 2 4 6 0 2 4 6 0 2 4 6

Cetyl Alcohol (CA)

6 6 2 2

Glycerol Monostearate

(GM) 6 2 6 2

Deionized water added up to 95

Residuals 5

92

separately The composition of Formulation_Ⅱ was introduced in Table 36 50 g

of each cream was prepared

Table 36 Formulation_Ⅱ of mimic creams prepared with varied concentrations of

fatty alcohols

3422 Formulation_Ⅲ

After preliminary analysis of mimic creams formulated with different concentrations

of chemically synthesized surfactants in Formulation_Ⅰ and Formulation_Ⅱ the

recipe was optimized and determined for bio-creams preparation In order to

compare the different performance between mimic creams and bio-creams those

mimic creams containing specific concentration of surfactants were freshly

prepared in Formulation_Ⅲ Details of the formulation were displayed in Table 37

other components such as preservatives fragrances and viscosity enhancers were

also not considered in this formulation with an assumption of 5 wt as residuals

In addition in replacement of paraffin mixed oils consisting of white soft paraffin

and light liquid paraffin plant oils including coconut oil and vegetable shortening

were introduced as bio-oils in the Formulation_Ⅲ for the preparation of eco-friendly

products Vegetable shortening is a fat made from vegetable oil which is in solid

state at room temperature

As a summarise in Formulation_Ⅲ nine big groups of creams were formulated

namely group P1 P2 and P3 referring to creams that formulated using paraffin

mix oils (white soft paraffin and light liquid paraffin) with SLES SLs and MELs as

surfactants respectively group C1 C2 and C3 referring to creams that formulated

using coconut oil instead group V1 V2 and V3 referring to creams that formulated

Mimic Creams

Ingredients F5 F6

Component (wt)

White soft paraffin 145 145

Light liquid paraffin 126 126

SLES 2 4

CA 5 6 7 5 6 7

GM 2 2


residuals 5

93

using vegetable shortening with SLES SLs and MELs as surfactants respectively

Prepared creams were stored in wide-opened plastic bottles for further analysis

94

Table 37 Formulation_Ⅲ of mimic creams and bio creams with optimized surfactant system

Mimic creams (P1) Bio-SLs-creams (P2) Bio-MELs-creams (P3)

Ingredients Component (wt)



Paraffin mix 271 Paraffin mix 271 Paraffin mix 271

SLES 2 4 6 Sophrolipids 2 4 6 MELs 2 4 6

CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2

Deionized water Up to 95 Deionized water Up to 95 Deionized water Up to 95

Mimic creams (C1) Bio-SLs-creams (C2) Bio-MELs-creams (C3)




Coconut oil 271 Coconut oil 271 Coconut oil 271


CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2


Mimic creams (V1) Bio-SLs-creams (V2) Bio-MELs-creams (V3)




Vegetable shortening 271 Vegetable shortening 271 Vegetable shortening 271


CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2


95


3431 Simplified Configuration

The simplified configuration applied for Formulation_Ⅰand Formulation_Ⅱ of

cream formulation was similar to the one introduced in chapter 3323 (see Figure

31) including a 300 mL Tall-form beaker (PYREX USA) an overhead stirrer (IKA

Overhead Stirrer RW 20 digital IKA England LTD) with a pitched blade impeller

and a heater (IKA Magnetic Stirrer C-MAG HS 7 IKA England LTD) The cooling

procedure was independent from this which is realised by removing the beaker

from the configuration followed by immersing in a big plastic container filled with

cold tap water

3432 Continuous Configuration

By upgrading the simplified apparatus a lab-scaled stainless jacket container

used as the mixing vessel was designed to replace the previous Tall-form beaker

which realized the continuous heating and cooling procedure This continuous

apparatus and its corresponding parameters are presented in Figure 32

For assembling this refined configuration a ThermosHAAKE DC1-L Heating

Circulator Bath (Thermo Scientific HAAKE Germany) was used for maintaining the

temperature while mixing connecting to the mixing vessel using heat resistant

silicon rubber tubes Rubber tube (a) was connected water bath out let with vessel

inlet and tube (b) was between vessel outlet and water bath inlet

For cooling rubber tube (c) controlled the transportation of cold water from the

water tap and circulated cooling was realized by simultaneously piping out water

to the storage sink with tube (d) opened Each rubber tube was equipped with a

stainless-steel clamp for flow control as required

96

344 Preparation Procedure for Standard Formulation

3441 Formulation_Ⅰand Formulation Ⅱ

The preparation procedure could be referred to that described in chapter 3324

Tiny change was made according to the composition of oil phase and aqueous

phase which is specified in Table 38

Table 38 Ingredients for cream preparation in Formulation_Ⅰand Formulation_Ⅱ


Creams (50g of each) in Formulation_Ⅲ were prepared using continuous

configuration The procedure for the cream preparation was introduced as below

Ingredients

Oil phase Aqueous Phase

White Soft Paraffin

Light Liquid Paraffin

Cetyl Alcohol (CA)

Glycerol Monostearate (GM)

Deionized Water

Sodium lauryl ether sulfate

(SLES)

Water Tap

Water

Bath

D

H

T

Parameters Values

D (mm)

H (mm)

T (mm)

60

137

70

Clam

p

Clamp

Clam

p

Clamp

(b)

(a) (c)

(d)

Storage

Sink


parameters that applied in Formulation_Ⅲ

97

1 Oil phase consisting of different oils CA and GM was prepared where

those components were weighed separately and mixed together in a

beaker followed by melting at 70 degC using a stir and heater

2 Liquid phase was then prepared while oil phase was kept homothermal by

the heater Surfactant in aqueous phase including SLES SLs and MELs

was weighed in the jacket container (mixing vessel) as required based on

the recipe Then specific amount of deionized water measured using

cylinder was added

3 The configuration was set up where rubber tubes were applied to connect

water bath jacked vessel and water tap As specified before tubes were

numbered (a) water bath outlet and vessel inlet (b) water bath inlet and

vessel outlet (c) vessel inlet and water tap and (d) vessel outlet and sink

4 Lower down the stainless-steel impeller in order to make sure that the

pitched blade was fully submerged in the water phase mixture Throttle the

connection between mixing vessel and water tap (c and d) and turn on the

water bath to fill the jacked of container Adjust the temperature of water

bath and set to 72plusmn2 degC Meanwhile power on the stirrer in order to mix

aqueous phase at 200 rpm

5 Monitoring the temperature in mixing vessel using a thermometer When it

reached to 70plusmn2 degC oil phase was added into the aqueous phase and the

mixing speed was increased to 500 rpm

6 After 10 minutes mixing water bath was turned off immediately and the

speed of agitator was turned down to 200 rpm Then the clamp on tube (c)

and (d) was removed while flow between water bath and mixing vessel

was chocked by clamping tube (a) and (b) Turn on the water tap in order

to cool the cream down for another 10 minutes to reach the room

temperature

7 When the preparation finished tubes were unplugged from the nozzles of

water bath and the tap and the rest circulated water in the jacket of the

container was poured out into storage sink for the reuse in the water bath

Creams were transferred into 100 mL wide-open plastic pots

35 Modification of Preparation Process

Effects of different mixing time mixing speed and different cooling procedure on

cream formulation was studied separately where a model cream was prepared

using different procedures and cream performances were analysed with the help

of droplet size distribution analysis and rheological measurements

98

351 Formulation of Model Creams

50 g of each model cream was prepared according to the recipe presented in Table

39

Table 39 Formulation of model creams used for studying the effect of different manufacturing strategies on cream performance

352 Preparation Procedure with Different Mixing Time During

Heating Procedure

Effect of different mixing time on the cream performance was studied with the help

of droplet size distribution measurement Model cream was prepared following

recipe mentioned above in the simplified configuration (see Figure 31) The

measurement was carried out following the procedure

1 Oil phase consisting of white soft paraffin liquid paraffin CA and GM was

prepared where those components were weighed separately and mixed

together in a beaker followed by melting at 70 degC using a stir and heater

Then the beaker containing oil phase mixture was kept in a water bath for

keeping temperature constant

2 Liquid phase was then prepared while oil phase was kept homothermal in

the water bath SLES was weighed in another beaker using as the mixing

vessel then specific amount of water was added Then the configuration

was set up where the heater and overhead stirrer was assembled properly

3 Put the mixing beaker containing liquid phase mixture on the heater then

lower the stainless steel impeller in order to make sure the pitched blade

fully submerged in the mixture Turn the heater on The temperature was

set at 90 degC at the beginning and controlled by a thermometer at around

Component

Weight concentration

(wt)


(wt)


(wt)

White soft paraffin 145 145 145


126 126 126

SLES 2 4 6

CA 6 6 6

GM 2 2 2

Residules

(not in the

formulation)

5 5 5

Deionized water added up to 100 added up to 100 added up to 100

99

70degC while mixing Meanwhile stirrer was powered on and mixing speed

was set at 200 rpm

4 When the temperature of liquid phase reached and maintained at 70 degC oil

phased was poured into aqueous phase and the mixing speed was

increased to 500 rpm

5 3 mL sample was then sequentially pipetted out from the mixing vessel at

different mixing times of 3 min 5 min 10 min 15 min and 20 min marking

as cream sample A B C D and E which is summarised in Table 310


different mixing procedure on product performance

6 Each cream sample was directed to Mastersizer 3000 for droplet size

distribution analysis

353 Preparation Procedure with Different Mixing Speed

During Heating Procedure

Effect of different mixing speed during heating procedure on the performance of

cream was studied and droplet size distribution measurement was carried out for

the analysis Model cream was prepared using the recipe specified in Table 39

using simplified configuration The measurement was carried out following the

procedure

1 Preparation of oil phase and liquid phase also the setting up of

configuration could be refer to the procedure introduced in chapter 352

2 Creams A B and C were then separately prepared at three different mixing

speed of 500 rpm 700 rpm and 900 rpm (Boxall et al 2010) For each

cream mixing time of 10 min was pre-set Then each of 1 mL hot cream

was pipetted out from the mixing vessel and transferred into different 20 mL

glass vials These 1 mL sample was prepared for the following droplet size

distribution analysis Mixing parameters are summarised in Table 311

Cream Sample

Mixing Procedure

Mixing Speed

(rpm)

Mixing Duration

(min)

A

500

3

B 5

C 10

D 15

E 20

100

Table 311 Specification of different mixing speeds during heating procedure applied for study the effect of different mixing procedure on product performance modified from Boxall et al 2010

354 Preparation Procedure with Different Cooling Procedure

Effect of different cooling procedure on the performance of cream production was

studied creams named A B C D and E were respectively prepared with different

cooling procedure (Roslashnholt et al 2014) and then the cream products were

analysed by rheological measurement The mixing procedure was kept constant

for each cream and the continuous configuration was applied Parameters for

different cooling procedures were introduced in Table 312

Table 312 Specification of different cooling procedures applied for study the effect of different cooling procedures on product performance adapted from Roslashnholt et al 2014

The procedure for the cream preparation could be referenced from that of

Formulation_Ⅲ in chapter 3442 After resting for 20 min prepared creams were

analysed with the help of rheometer

36 Characterisation Methods

Creams were characterised using rheological measurements for analysing their

flow properties and differential scanning calorimetry for analysing their

thermodynamic properties Microscopy and droplet size distribution were also

Cream Sample

Mixing Procedure

Mixing Speed

(rpm)

Mixing Duration

(min)

A 500

10 B 700

C 900

Cream

Mixing Procedure Cooling Procedure

Mixing Speed

(rpm)

Mixing Duration

(min)

Stirring speed

(rpm)

Cooling Duration

(min)

A

500

10

200 10

B 0 10

C 300 10

D 200 5

E 200 20

101

conducted on some desired creams for providing information for microstructure

analysis

361 Rheology

Rheological test is a useful method for rapidly predicting the performance of a

material such as spreadability rigidity and thixthotropy where non-linear steady

state rotational test and linear oscillatory test are two main rheological

characterisation methods Basic principles and background knowledge of rheology

applied in this study will be preliminary introduced mainly including viscosity with

corresponding flow models and viscoelasticity with corresponding models

3611 Theory of Flow Behaviour

The two-plate model generally used to express the rotational tests and define

rheological parameters where flow goes through two parallel plates (Barnes et al

1989) An external force is applied constantly to the upper plate along positive

direction of axis resulting a velocity while the lower plate is stationary With the

assumption that no wall-slip effects and laminar flow is involved the adherence of

flow to surfaces of both plates and the flow is imagined in the form of numerous

layers that clinging to each other The flow rate of one flow layer is different from

another leading to relative movement and velocity gradient between flow layers

and the velocity Therefore a shear force F which is parallel to the flow layer arises

between two layers If the shear area is A the shear stress τ can be expressed in

Equation 32

120591 =119865

11986032

Where τis shear stress F is shear force A is shear area

Shear strain 120516 is defined as the displacement (deformation) of the plate (Δx)

divided by the distance between two plates (Δy) shown in Equation 33

120574 =∆119909

∆11991033

Where γis shear strain Δx is displacement of the plate Δy is distance between

two plates

Shear rate is defined as the time rate of shear strain which is notated using

with a unit of s-1 shown in Equation 34 This value is applied to indicate the flow

velocity u

102

=119889120574

119889119905=

119889

119889119905(

119889119909

119889119910) =

119889

119889119910(

119889119909

119889119905) =

119889119906

11988911991034

Where is shear rate u is flow velocity

For Newtonian fluids shear stress is proportional to the velocity gradient and the

coefficient is known as viscosity μ with a unit of Pa∙s which is shown in Equation

35 and 36

120591 = minus120583 (119889119906

119889119910) 35

120583 =120591

36

Where μis the viscosity for Newtonian fluids

Viscosity μ is constant for Newtonian fluids indicating an independent of internal

flow resistance is independent of external forces Whereas for non-Newtonian

fluids known as structured or complex fluids the viscosity η is inconstant that

alters with the external stress (see Equation 37) The classification of non-

Newtonian fluids is shown in Table 313 and their flow behaviours are plotted in

Figure 33 displaying shear stress (τ) and viscosity (η) dependent on shear rate

() (Mezger 2020)

120591 = minus120578 (119889119906

119889119910) 37

Where η is the viscosity for non-Newtonian fluids

103

Table 313 Classification of Non-newtonian fluids according to Mezger 2020

3612 Theory of Rheological Measurements

Various rheological measurements were carried out experimentally to study the

flow properties of materials such as steady state shear test dynamic oscillatory

sweep test creep-recovery test and stress relaxation test Generally these

experiments are carried out by exerting an external force (shear or sweep) on the

product sample simulating conditions that encountered during product life and the

obtained rheological profiles will be introduced in this part

Categories Classification

Pure viscous

fluid

Time independent

Newtonian fluid

Pseudoplastic fluid Dilatant fluid

Non-Newtonian fluid

Binghamrsquos fluid Plastic fluid

Yield- Pseudoplastic fluid Yield- dilatant fluid

Time dependent

Thixotropic fluid

Rheopectic fluid

Viscoelastic fluid More types of fluid

Figure 33 Flow behaviour of fluids plotted in shear stress-shear rate (left) and viscosity-shear rate (right) diagram according to Mezger 2020

104

36121 Steady state rotational shear test (non-linear)

Steady state rotational test involves forcing sample being sheared under increased

stress or rate within pre-set range Through simulating processes that the sample

will experience in real practice such as spreading the rheological properties

including shear thinning or thickening behaviour and apparent viscosity could be

predicted (Mezger 2020) Figure 34 schematically illustrates the sample laded

between bob (cone in the fig) and plate geometry provided with the generate shear

profile The profile could be interpreted with two-parallel plate model where flows

are depicted as layers sliding over each other

Rheological profile of time-independent shear thinning fluids

Rotationally shearing sample within a wide range of shear stress from low to high

the change of apparent viscosity of a sample with increased shear stress is

obtained and the rheological profile is usually logarithmic presented Take shear

thinning fluid as an example a typical S-shape flow curve is generally achieved

and plotted in a log (viscosity)-log (shear rate or shear stress 120591) graph shown in

Figure 35 (Tatar et al 2017) During 1st Newtonian plateau zero shear viscosity

(η0 ) indicates the strength of system microstructure to resistant external forces

after exceeding the yield stress it starts to flow and another plateau will be

achieved when molecules already realigned in a same direction and no further

decrease in viscosity witnessed showing infinite shear viscosity (ηinfin ) In addition

the orange curved line in the figure between 1st Newtonian Plateau and shear

Figure 34 Schematic diagram of steady state shear and generated shear profile according to Mezger 2020

105

thinning is defined as the transition region where the microstructure of system

starts to alter

Various mathematical models were developed and applied to interpret time-

independent non-Newtonian flow behaviours The constitutive equations of non-

Newtonian models are summarised in Table 314 (Mezger 2020) where τ is the

shear stress is the shear rate and the apparent viscosity (effective viscosity) is

notated as 120578119890119891119891 The application of models fitting in the S-shape curve is presented

in Figure 35

Table 314 Non-Newtonian models with constitutive equations according to Mezger 2020

Models Constitutive equations

Bingham Model

Describe Bingham plastic

fluids which exhibit a

Newtonian behaviour (linear

relationship between shear

stress and shear rate) when

above yield point

120636119942119943119943 = 120636119942119943119943infin +120649119962

Where

120591119910 is the yield shear stress

120578119890119891119891infin is the limiting viscosity of

plastic fluids above the yield stress

Ostwald-de Waele (power law)

Model

120636119942119943119943 = 119948(119931) ∙ 119951minus120783

Where

119897119900119892 or 119897119900119892120591

119897119900119892

120578

1st Newtonian

Plateau

2nd Newtonian Plateau Shear Thinning

1205780

120578infin

Cross Bird-Carreau-Yasuda model

Ellis model

Sisko model

Figure 35 Qualitative S-shape rheological curve for typical shear thinning fluids and corresponding model fitting range according to Tatar et al 2017

106

Represent shear thinning

region in 119949119952119944120636 minus 119949119952119944 or

119949119952119944120636 minus 119949119952119944120649 curve

Cannot fit in 1st Newtonian

plateau

k is the flow consistency index (dependent on temperature)

n is the flow behaviour index

Herschel-Bulkley Model

Combination of Bingham and

power law model

Describe the fluids which

exhibit shear thinning

behaviour (non-linear



above yield point

120649 = 120649119962 + 119948(119931) ∙ 119951

Where



Bird-Carreau-Yasuda Model

Interpret 1st Newtonian

plateau and shear thinning

region in 119949119952119944120636 minus 119949119952119944 curve

Describe pseudoplastic flow or

thermoplastic materials for

which there is a typical

curvature of the viscosity in

the transient area

Involving two fitting

parameters 119847 and 120524

120578119890119891119891() minus 120578infin

1205780 minus 120578infin= (1 + |120582 ∙ |119886)

119899minus1119886

120578119890119891119891() = 120578infin + (1205780 minus 120578infin)

∙ (1 + |120582 ∙ |119886)119899minus1

119886

Where

120582 is the relaxation time constant 1

120582frasl is the critical shear rate at

which viscosity begins to decrease

119899 is the power law index giving the degree of shear thinning

119886 describe the width of the transition region between low shear rate and when the power law region starts equals 2 in original model

When the viscosity (120578infin) at infinite shear rate is negligible the model is simplified

as follow

120636119942119943119943() =120636120782

(120783 + |120640 ∙ |119938)119951minus120783

119938

Cross Model

Similar to the Bird-Carreau-

Yasuda model describing

both Newtonian and shear

120578119890119891119891() minus 120578infin

1205780 minus 120578infin=

1

1 + (119870 ∙ )1minus119899

Where

119870 is the cross constant indicating the onset of shear thinning

107

thinning behaviour in 119949119952119944120636 minus

119949119952119944 curve



When 120578infin is negligible the model is simplified

120636119942119943119943() =120636120782

120783 + (120636120782 ∙

120649lowast )120783minus119951

Where 120591lowast =1205780

119870frasl

Ellis Model

Describe time-independent

shear-thinning non-Newtonian

fluids in 119949119952119944120636 minus 119949119952119944120649 curve

focusing on the 1st Newtonian


region

120636119942119943119943() =120636120782

120783 + (120649

120649120783120784frasl

)

120630minus120783

Where

12059112frasl represents the shear stress

when the apparent viscosity

120578119890119891119891 decreased to 120578119890119891119891

2frasl


Sisko Model




focusing on the shear thinning

and 2nd Newtonian plateau

region

120636119942119943119943() = 119922 ∙ 119951minus120783 + 120636infin

Where

K is the cross constant indicating the onset of shear thinning

n is the power law index

Rheological profile of time-dependent fluids

The flow properties of time-dependent non-Newtonian fluid such as thixotropic and

rheopectic fluids depend on both of the amount and the duration of external forces

The hysteresis loop analysis is an applicable method for their study As shown in

Figure 36 where shear stress against shear rate thixotropic fluids presents a

clockwise loop while rheopectic fluids shows an anticlockwise one The larger the

loop area greater extend is the dependent on time (Maazouz 2020) Conversely

if the loop area is zero flow behaviour of the material is time independent Also the

area between curves represents energy loss of the system and maximum viscosity

is identified from the apex

108

36122 Creep and recovery test

Creep test is applied for the analysis of viscoelasticity of complex fluids where the

sample is under a constant shear stress in linear viscoelastic region over a period

of time and the resultant shear strain is measured In the following recovery step

the stress is removed and the shear strain in the system is measured for a period

of time Hookrsquos Law representing by spring as elastic response (Equation 38) and

Newtonrsquos Law representing by dashpot as viscous element (Equation 39) are

basic theories for viscoelasticity interpretation which is schematically presented in

Figure 37 (Mezger 2020)

Shea

r st

ress

120591

Shear rate

Thixotropic fluid

Rheopectic fluid

Fτ

Fτ

Δx

Δx

Figure 36 Typical hysteresis loop of shear stress-shear rate behaviour for thixotropic and rheopectic material according to Maazouz 2020

Figure 37 Schematic diagram of spring represents elastic behaviour (left) and dashpot represent for viscous behaviour (right)

109

120590119866 = E ∙ ε119866 38

Where σG is tensile stress E is the Youngrsquos modulus εG is the spring strain

120591120578 = 120578 ∙119889120574120578

119889119905= 120578 ∙ 120578 39

Where τy is the shear stress 120578 is the shear rate η is the viscosity

The responses of linearly elastic material (spring element model) and viscous liquid

(dashpot element model) subjecting to creep and recovery test is presented in

Figure 38 When given an external force at constant shear stress of 1205910 from

time 1199050 = 0 to 1199051 the linearly elastic material responses an instant strain 휀0 =1205910

119864frasl

at 1199050 = 0 lasting until t1 when the load is removed (Figure 38 (b)) However as

Figure 38 (c) presented the strain of dashpot increased gradually when the

external force applied building up the strain to 1205740

=1205910

120578(1199051 minus 1199050) until t1 and the strain

that built up is permanent and irreversible after the force removed

The Maxwell fluid model

Maxwell model consists of a spring representing for the instantaneous response of

the elastic solid in tandem with a dash pot presenting the react of the viscous fluid

showed in Figure 39 In theory when the force added to the Maxwell model the

system is preliminary dominated by elastic E during very short time followed by

the viscous behaviour emerging and η is gradually predominant The equation for

Maxwell model can be deduced to Equation 310

dγ119905119900119905119886119897

dt=

1

119864∙

dτ119905119900119905119886119897

dt+

120591119905119900119905119886119897

120578310

Where E is the Youngrsquos modulus τtotal is the total shear stress γtotal is the total

shear strain η is the viscosity

τ

t t0=0 t1

τ

0

a ε

t t0=0 t1

1205980 1205980 =

1205910119864frasl

b γ

t t0=0 t1

γ

0

1205740 =1205910

120578(1199051 minus 1199050)

c

Figure 38 Creep and recovery test (a) and expected response of different materials response of linearly elastic material (b) response of viscous liquid (c)

110

Maxwell model could be used to predict Newtonian behaviour especially for

viscoelastic liquid Figure 310 shows the stress applied to Maxwell model system

(a) and the strain response of creep and recovery test (b) The model gives an

instant elastic response ( 120634120782 =120649120782

119916frasl ) at t0 then the behaviour during most of creep

loading duration presents strain linearly increasing with time and the model

showing viscous dominant governing by the dashpot When the external force is

removed the elastic strain which is valued 120649120782

119916frasl is recovered right away a

permanent strain (1206341) caused by the dashpot remains (Mezger 2020)

The Kelvin-Voigt solid Model

Kelvin-Voigt is made up of a spring and a dashpot connected in parallel shown in

Figure 311 The spring and the dashpot will undergo the same strain when

external force applied and the total stress is the sum of individually experienced

stress of spring and dashpot Equation 311 expressed the responded strain and

time in Kelvin-Voigt model

ε

t t0=0 t1

휀0

b

휀0

τ

t t0=0 t1

τ0

a

휀1

휀1

η η

F F

η

E

∆119909120578

∆119909119864 F

t=T t=T t=T+ΔT

E E 120591119866 = E ∙ ε119866

120591120578 = 120578 ∙119889120574120578

119889119905

Figure 310 Schematic diagram of Maxwell model

Figure 39 Creep and recovery test (a) and expected response of Maxwell model (d)

111

119889γ119905119900119905119886119897

119889119905=

120591119905119900119905119886119897

120578minus

E

120578∙ γ119905119900119905119886119897 311



From there strain is exponentially decays with time Thus Voigt model could be

used for predicting creep response for viscoelastic materials Figure 312 presents

response of Kelvin-Voigt Model to a constantly external stress 120649120782 lasting from 1199050 =

0 to 1199051 the dashpot hinders the stretching of spring and takes stress 120649120782 and

response with an increasing of strain with a slope of 120649120782

120636frasl As strain increased part

of the stress will transferred to the spring from the dashpot and the slope of the

increased strain changes to 120649120636

120636frasl (where 120649120636 is the residual stress in dashpot)

When all the stress is taken by the spring the maximum strain is reached which

is 120649120782

119916frasl At t1 when the stress is removed the strain decreased gradually No

permanent strain remains eventually and the system will achieve full recovery

because the spring will eventually contract to its original position and the parallel

arrangement allows same strain for spring and dashpot (Mezger 2020)

120574120578

120591120578 = 120578 ∙119889120574120578

119889119905

γ119866

120591119866 = G ∙ γ119866

F 120591119905119900119905119886119897

Figure 311 Schematic diagram of Kelvin-Voigt model

112

Burgers Model

Compared with creep-recovery response between Maxwell and Kelvin-Voigt

models the ever-decreasing strain rate type creep and anelastic recovery could

be predicted with Kelvin-Voigt model but not with Maxwell one but the

instantaneous elastic response and permanent strain could be only witnessed with

Maxwell model In real practice some advanced models involved three or more

elements are proposed for the interpretation of more complex materials such as

the Standard Linear Model and Burgers Model Burgers model is applicable in the

rheological analysis for viscoelastic models which is schematically as a Maxwell

model in series connection with a Kelvin-Voigt model (Figure 313)

As seen in Figure 313 (a) showing strain response of Burgers model to external

stress spring element Ⅰ stretches immediately resulting in an instantaneous strain

followed by a creep strain consisting of a delayed elastic response (E3 η2_C) and a

linear viscous response (η4) As soon as the force is removed an elastic response

caused by spring element Ⅰ (E1) is initially observed after which the recovery of

Kelvin-Voigt element (paralleled system involving viscous element Ⅱ (η2) and

120574

t t0 t1

b τ

t t0=0 t1

τ0

a

F τtotal

E3

Ⅲ

η2

Ⅱ E1

Ⅰ

η4

Ⅳ

120598

t

t0 t1

E1_R

E3 η2_C

η

4

E1_C

E3

η2_R

Creep

strain

Permanent

strain

b) a)

Figure 312 Creep and recovery test (a) and expected response of Voigt model (b)

Figure 313 Typical creep and recovery response (a) for Burgers model accompanied with its schematic diagram (b)

113

spring element Ⅲ (E3)) shows anelasticity Permanent strain exists due to the

viscous deformation by viscous element Ⅳ (η4)

Instead of the strain compliance J(t) is normally applied for the presentation of

creep and recovery response curve which is expressed as the measured strain

divided by the applied stress shown in Equation 312

119869(119905) =120574(119905)

120591312

Where J is the compliance τis the applied stress γ is the measured strain

Figure 314 simply illustrates response of pure viscous and elastic materials

subjecting to creep test in terms of interpretation of creep compliance against time

log t t0

log c

reep

com

pli

ance

J

Elastic material

Viscous material

Figure 314 Response of viscous material and elastic material to creep test expressed with creep compliance with time in log-log plot

114

36123 Dynamic oscillatory sweep test (linear)

Dynamic oscillatory sweep test is often carried out to obtain the similar information

as creep and recovery test for the viscoelasticity characterisation where a shear

strain with a sinusoidal waveform is usually induced to the system expressing with

two-plate model shown in Figure 315

In oscillatory shear test one type is applying stress (torque) to the bob and

measuring the resultant strain γ (angular displacement) the other is controlling

the strain and then measuring the stress When the frequency of sinusoidal wave

is 119891 the complex shear strain that applied to a material is expressed in Equation

313 (Mezger 2006)

120574 = 120574119898119886119909 sin 120596119905 = 120574119898119886119909119890119894120596119905 313

Where 120596 is angular frequency (120596 = 2120587119891 ) with a unit of radmiddots-1 120574119898119886119909 is the

complex shear strain amplitude t is time with unit of second 119894 = radicminus1

Generally the corresponding linear response of material in terms of complex shear

stress is expressed in Equation 314

120591 = 120591119898119886119909 sin(120596119905 + 120575) = 120591119898119886119909119890119894(120596119905+120575) 314

Where 120575 is defined as phase angle with a unit of degree (deg) 120591119898119886119909 is complex stress

amplitude

When 120575 = 0deg the stress in material is proportional to the strain which is known to

be in phase and the material is purely elastic If the phase angle 120575 equals to 90deg

0

deg

90

deg

180

deg

270

deg

360

deg

0deg360

deg

90

deg

180deg

27

0deg

90

deg 27

0deg

Figure 315 Two-plate model for oscillatory shear test and the applied oscillatory shear profile

115

the stress is proportional to the rate of strain where the stress and strain is said to

be out of phase the material is purely viscous For a material showing both of

elastic and viscous properties the response of which contains both in phase and

out of phase contributions so phase angle will lie between of two extremes (0deg lt

120575 lt 90deg) (Lade et al 2019)

Complex shear modulus (119866lowast ) is introduced for quantifying the resistance of a

material to deformation which is the combination of viscous component and elastic

component It could be expressed as the ratio of applied stress (strain) to the

response in terms of strain (stress) see Equation 315

119866lowast =119888119900119898119901119897119890119909 119904119905119903119890119904119904 119886119898119901119897119894119905119906119889119890

119888119900119898119901119897119890119909 119904119905119903119886119894119899 119886119898119901119897119894119905119906119889119890=

120591119898119886119909120574119898119886119909

frasl 315

Where G is complex shear modulus τmax is complex stress amplitude γmax is

the shear strain

The viscous component contributing to complex modulus is defined as loss

modulus (119866primeprime) representing for energy loss the elastic component contributing to

complex modulus is defined as storage modulus (119866prime) representing for energy

storage Equation 316~319 mathematically expressed of relationships between

these terms

119866prime = 119866lowast cos 120575 =120591119898119886119909

120574119898119886119909cos 120575 316

119866primeprime = 119866lowast sin 120575 =120591119898119886119909

120574119898119886119909sin 120575 317

119866lowast = radic119866prime2 + 119866primeprime2 = 119866prime + 119894119866primeprime 318

tan 120575 =119866primeprime

119866prime319

Where Grsquo is storage modulus Grsquorsquo is loss modulus G is complex shear modulus

τmax is complex stress amplitude γmax is the shear strain δis phase angle

Complex viscosity is determined during oscillatory shear test which is the

frequency dependent viscosity indicating the total resistance of material to flow or

deformation defined with Equation 320

120578lowast =119888119900119898119901119897119890119909 119904119905119903119890119904119904 119886119898119901119897119894119905119906119889119890

119888119900119898119901119897119890119909 119904119905119903119886119894119899 119903119886119905119890 119886119898119901119897119894119905119906119889119890=

120591119898119886119909

120574119898119886119909=

120591119898119886119909

120574119898119886119909119894120596=

119866lowast

119894120596320

116

Similar to the definition of 119866lowast 120578lowast could be regarded as the combination of real part

and imaginary part as well see Equation 321 and 322 (Mezger 2020)

120578lowast = 120578prime + 119894120578primeprime 321

120578prime =119866primeprime

120596 120578primeprime =

119866prime

120596322

Where 120578prime represents viscosity for real portion 120578primeprime represents viscosity for the

imaginary portion

Oscillatory amplitude sweep

Oscillatory amplitude sweep refers to the test where a material is being oscillated

sheared by varying the amplitude of the deformation or shear stress (generally

with strain) while keeping the frequency (generally with angular frequency) as

constant The typical response of a complex fluids to an oscillatory amplitude

sweep is shown as the storage modulus 119866prime and loss modulus 119866primeprime changing with the

increased strain or stress (Mezger 2020) Linear viscoelastic region (LVER) is a

key achievement by carrying out oscillatory amplitude tests where moduli are

independent with applied strain or stress and remaining constant at a plateau value

The value of storage modulus 119866prime in LVER gives the information of rigidity of

material at rest while that of loss modulus 119866primeprime reveals the information of viscosity

of undisturbed material Another point of oscillatory amplitude is the determination

of crossover point of curves of 119866prime and 119866primeprime which is known as the flow point after

which the dominate contribution to the material system will change

Oscillatory Frequency sweep

Oscillatory frequency sweep refers to the test where a material is being oscillatory

sheared varying the frequency at a constant strain or stress amplitude The storage

modulus 119866prime and loss modulus 119866primeprime is quantified against angular frequency which

is measured in rad s-1 Lower frequencies indicating longer time scale and high

ones for short time scale Due to time-dependent property of viscoelastic materials

moduli are expected to change with varied frequency Small amplitude oscillatory

frequency sweep that applied in this study refers to the test carried out during LVER

whereas large amplitude oscillatory frequency sweep refers to nonlinear response

of materials due to large deformations or structural disruptions and material

functions are not only dependent on frequency which will not be discussed in

details here

117

Small Amplitude Oscillatory Shear (SAOS)

As previous introduction at low amplitudes of strain range (LVER) material is

expected to give linear response in terms of shear stress when subjecting to

applied strain Introducing relaxation time 120582 (120582 =120578

119866) response of Maxwell model in

terms of 119866prime and 119866primeprime is expressed with Equation 323 is obtained (Mezger 2020)

119866prime =12058212057812059621205740

1 + 12058221205962 119866primeprime =

1205781205961205740

1 + 12058221205962323

It can be conclude from equations above at low frequencies 119866prime ⋉ 1205962 and 119866primeprime ⋉ 120596

indicating that 119866primeprime is larger than 119866prime so the response of Maxwell model-material is

viscous dominant while at very high frequencies the situation is reversed (Figure

316 (a)) As for Voigt model which describes viscoelastic solids storage

modulus 119866prime is a constant value and independent with time and loss modulus 119866primeprime is

linearly increase with frequency At very low frequencies solid behaviour

dominates With the increase of frequency storage modulus remains constant and

loss modulus increases linearly therefore 119866primeprime will be larger than 119866prime at high

frequencies and material behaves more liquid-like (Figure 311 (b)) (Mezger 2020)

Log

mo

dul

us

Log angular frequency

119866primeprime

119866prime

(a)

Maxwell model (For viscoelastic liquid)

Log

mo

dul

us


119866prime

119866primeprime

(b)

Voigt model (For viscoelastic solid)

Figure 316 Typical frequency response of Maxwell model for a viscoelastic liquid (a) and Voigt model for a viscoelastic solid (b)

118

3613 Experimental Section

36131 Measuring System and Geometries

In this project the flow properties of manufactured creams were examined after 20

minutes from preparation using a controlled stress AR 2000 rheometer (TA

instrument) equipped with a cone and plate geometry (cone angle of 1deg59 and

radius of 40 mm) Samples were loaded on the plate and the cone was lowered

to reach a gap of 57 mm with the plate The physical model of rheometer system

is presented in Figure 317 As the flow resistance exist in the flow behaviour and

the internal friction process occurring between particles will result in viscous

heating of the sample the water bath is used for controlling the temperature at a

required value for the experiment

In the schematic diagram Figure 318 Ω represents for angular velocity of the cone

(Ω = 212058711989960frasl where n is the rotor speed with the unit of 119903 ∙ 119898119894119899minus1) T represents for

the resulting torque (with the unit of 119873 ∙ 119898) which is needed to rotate the cone Ω

T and the total force F normal to the fixed plate are quantities that were measured

in the experiment Rc is the radius with a unit of m and α is the gap angle with a

unit of rad

According to the research of Khan and Mahmood in the measuring system with

cone and plate geometry the shear rate 119888 could be expressed with the Equation

324 (Hellstroumlm et al 2014)

Water bath Computer Rheomete

r

Figure 317 Physical model of rheological measuring system

119

119888 =1

119905119886119899120572∙ Ω = 119872 ∙ Ω 324

Where M represents for shear rate factor with the unit of rad-1 This value is

constant for a specific cone and plate measuring system 119888 represents for shear

rate with the unit of s-1

The shear stress can be related to the measured torque see Equation 325

assuming that the torque working on the cone equals to that working on the plate

(Mezger 2020)

120591119888 = (3

2120587 ∙ 1198771198623) ∙ 119879 325

Where 120591119888 represents for shear stress on cone and plate with the unit of Pa

Then Equation 326 for viscosity function is obtained

120578(119888) =120591119888

119888= (

3 ∙ 119879

2120587 ∙ 1198771198623) ∙

120572

Ω326

Where 119888 is the shear rate η is the viscosity τc is the shear strain T is the torque

αis the gap angle Ω is the angular velocity Rc is the radius

36132 Measuring Procedure

After 20 min of preparation rheological tests were at least duplicated carried out

for every sample where samples were freshly loaded following consistent routine

in order to achieve the reproducible results The procedure of characterisation is

summarised as below where parameters that selected are according to the results

of characterisation of E45 cream (see Chapter 4)

α

Rc

Cone

Plate

Tested sample

Ω

Transducer for torque measurement Torque T

Figure 318 Schematic diagram of cone and plate geometry

120

1 Steady state shear test (SSS) was firstly performed on creams The

Sample was rotational sheared under varied shear stress thus viscosity

change with shear stress was obtained Details of test including conditions

and setting parameters are displayed in Table 315

Table 315 Parameters for steady state shear test (SSS)

Conditioning Step for SSS

Geometry gap 57 mm Temperature 25 ordmC

Equilibrium time 10 minutes Pre-shear procedure

No pre-shear

Steady State Flow Step

Variables Shear stress ranging from 1 Pa to 300 Pa

Number of points 10 points per decade in log mode

2 Oscillatory sweep test was then performed Oscillatory amplitude (strain)

sweep (OSS) was performed in order to determine linear viscoelastic region

(LVER) Then an oscillatory frequency test (OFS) was carried out at a

constant strain selected within LVER Details of tests are displayed in

Table 316 and 317

Table 316 Parameters for oscillatory strain sweep test (OSS)

Conditioning Step for OSS


Equilibrium time 10 minutes

Pre-shear procedure No pre-shear

Oscillatory Strain Sweep Step

Variables strain ranging from 0001 to 1000

Controlled variable Frequency controls at 1 Hz


Table 317 Parameters for oscillatory frequency sweep test (OFS)

Conditions for OFS


121

Equilibrium time 10 minutes Pre-shear procedure No pre-shear

Oscillatory Frequency Sweep Step

Variables Frequency ranging from 001Hz to 100 Hz

Controlled variable strain within LEV range selected from oscillatory amplitude test (01 for mimic creams at 001 for bio creams)


3 Creep and Recovery test for creams was carried out for further

analysis of their viscoelastic properties Constant stress was applied on

the sample for a period of time followed by a strain relaxation process

where external stress was removed Details of the test are introduced in

Table 318

Table 318 Parameters for creep and recovery test

Conditions for creep and recovery test

Geometry gap

57 mm Temperature 25 ordmC

Equilibrium time

10 minutes Pre-shear procedure No pre-shear

Creep Step

Controlled variable

Shear stress of 10 Pa for mimic creams shear stress of 1 Pa for bio creams

Duration 30 minutes

Recovery Step

Controlled variable

Shear stress of 0 Pa Duration 30 minutes

Number of points

10 points per decade in log mode

362 Differential Scanning Calorimetry (DSC)

3621 Theory

Thermal analysis refers to the measurement that monitors the properties of a

material changing as a function of temperature or time The sample is prone to be

heated melted oxidized and decomposed while increasing temperature as a

122

result melting point crystallization behaviour glass transition temperature and

stability are acknowledged Differential scanning calorimetry (DSC) is a type of

thermos analysis method where the difference in the heat to or from the sample

and the reference (air) was measured against temperature while the sample is

heated or cooled In practice two types of DSC measurement theory are widely

applied which are known as heat-flux DSC and power compensation DSC (Houmlhne

et al 2013)

36211 Power compensation DSC

For power compensation DSC the input energy that applied to the sample and

reference (air) for maintaining their temperature difference close to zero is

measured while the sample is scanned This resulting energy difference is

proportional to heat flow and recorded as a function of sample temperature The

schematic configuration of power compensation DSC is depicted in Figure 319

(Danley 2002)

The sample and reference are enclosed in two separate aluminium or platinum

pans (with lids) placing in two platforms where they are heated up by two individual

heating sources The temperature of sample (TS) and reference (TR) are controlled

to be equal (∆T= TS-TR=0) through supplying differential power input ∆P when the

sample undergoing endothermal or exothermal process which is monitored by

separate two sensors (platinum resistance thermocouples or thermometers) The

power signal ∆P is proportional to the endothermic and exothermic heat

Temperature

programmer

(∆T=0)

Reference Sample

Individual heaters

pans (with lids)

Platinum

resistance

thermomete

rs (TR)

Insulating heat sink

Platinum

resistance

thermomete

rs (TS)

Controller ∆

P


123

36212 Heat flux DSC

For heat flux DSC the sample and reference (air) are heated by a single heating

source resulting in same heat flowing into them and the temperature difference

between them due to variation of thermal properties (enthalpy or hear capacity) of

the sample while scanning is measured (Drzeżdżon et al 2019)

In terms of the configuration of heat flux DSC seen from Figure 320 sample and

reference (usually air) encapsulated in pans are placed together in an insulating

heat sink A heat flux plate (usually a constantan disc) is connected to the heater

(not shown in figure) and provide heat flow to the sample and reference platforms

through heat resistor (not shown in figure) Thermocouples junctions that

produces voltage due to temperature difference are used as sensors in the

configuration A Chromel wafer (grey block underneath the pan) is equipped at the

bottom of pans with which chromel-constantan thermocouples are formed for

detecting the differential temperature ∆T between sample and reference This is

measured as the voltage difference ∆U Alumel wires are connected to the chromel

wafer resulting chromel-alumel thermocouple junctions by which the

temperatures of sample (TS) and reference (TR) are measured individually

Temperature programmer helps control temperature to satisfy the experimental

demand with the help of another thermocouple set in the heater As the

temperature difference between sample and reference is directly related to the

Reference Sample

Temperature programmer

T

S

T

R

Heat flux

plate

Pans (with lids)

Insulating

heat sink

Thermocouples

Material 1

(Alumel wire) Material 2

(Chromel wire)

∆

T

Figure 320 Schematic diagram of heat flux DSC

124

differential heat flow for an accurate detection of the differences of temperature a

vacuum working environment with purge gas flow through the sink is practically

applied

In heat flux DSC the response of sample could be expressed with Equation 327

(Houmlhne et al 2013)

119902 =119889119867

119889119905= 119862119901

119889119879

119889119905+ 119891(119879 119905) 327

Where 119902 represents for heat flow with a unit of J min-1 which is the DSC heat flow

signal 119862119901 is the specific heat with a unit of J g-1 ordmC-1 119889119879

119889119905 is the heating rate with a

unit of ordmC min-1 119891(119879 119905) is the kinetic response of sample in terms of heat flow as a

function of time at an absolute temperature


36221 Measuring System

TzeroTM DSC 2500 system (TA Instrument) was applied for measuring

thermodynamic properties of creams in this project equipped with TRIOS software

As the sample and reference calorimeters are rarely designed to be symmetrical

in real practice the conventional calculation of heat flow based on those

assumptions involves unavoidable error Tzero DSC 2500 system equips with

another Tzero thermocouple as a control sensor in the middle position of sample

and reference platforms which allows measuring the asymmetry in terms of

imbalanced heat flow at sample and reference calorimeters The schematic of

Tzero heat flow model is shown in Figure 321

Sample Reference T0

RS Rr

TS TR

qS qR

CS CR

Tzero

thermocouple

Figure 321 Schematic diagram of Tzero measurement model for DSC

125

Thus the heat balance equation for sample and reference are written as Equation

328 and 329 (Arias et al 2018)

119902119878 =1198790 minus 119879119878

119877119878minus 119862119878

119889119879119878

119889119905328

119902119877 =1198790 minus 119879119877

119877119877minus 119862119877

119889119879119877

119889119905329

Where 1198790 represents the temperature for control 119862119878 and 119862119877 represent for heat

capacity of sample sensor and reference sensor separately Then the resultant

Tzero heat flow equations are obtained (see Equation 330~332)

119902 = 119902119878 minus 119902119877 = minus∆119879

119877+ ∆1198790 (

1

119877119878minus

1

119877119877) + (119862119877 minus 119862119878)

119889119879119878

119889119905minus 119862119877

119889∆119879

119889119905330

∆119879 = 119879119878 minus 119879119877 331

∆1198790 = 1198790 minus 119879119878 332

Where ∆119879 is the measured temperature difference between sample and reference

and ∆1198790 is the measured base temperature difference between sensor sample


a) Sample cells preparation

Proper sample preparation was carried out for the following measurement 5~10

mg of samples including creams and raw materials (mixed paraffin oils Sodium

Laureth Sulphate Cetyl Alcohol Glycerol Monostearate SLs and

Mannosylerythritol lipids) were weighed into the alumina pan respectively

followed by being hermetically sealed using Tzero sample encapsulation press kit

Another empty reference pan was also enclosed with the same procedure

b) Method setting for DSC measurement

Test was edited using TRIOS software Details of sample information was entered

including sample and reference names with assigned pan location number

measured weight of samples and pans (including lid) Autosampler was applied for

precisely picking up sample and reference pans from their location and releasing

them at their position in the cell thereby realising consistent cell closure and

improving the reproducibility of the test

126

A method for analysing mimic cream in terms of thermodynamic properties was

created in the software for the analysis according to cream system The sample

was heated from 25 ordmC to 90 ordmC at a constant rate of 3 ordmC min-1 An equilibration

step was taken at 90 ordmC for three minutes followed by a backward cooling process

to -20 ordmC at the same scan speed of 3 ordmC min-1 After being maintained equilibrium

at -20 ordmC for three minutes the sample was undergoing a heating process to 25

ordmC As a result thermal properties of samples during heating and cooling cycles

were measured presenting as a thermo-diagram

363 Droplet Size Distribution Analysis

3631 Theory

Droplet size distribution (DSD) of the cream was characterised using the technique

of laser diffraction When light from laser beam passing through different sizes of

particles or droplets different angle of light diffraction will be generated As

schematic diagram illustrates (Figure 322) large droplets scatter light at narrow

angles while small droplets scatter light at wide angles (Perlekar et al 2012)

A simplified schematic diagram of optical part of laser diffraction droplet size

analyser is shown in Figure 323 When a sample containing droplets subjects to

the laser beams a light intensity diffraction pattern is generated from the forward

scattered light and displayed on a detecting plane Light being diffracted from side

and backward will be detected by side scatter light sensor and backward scatter

light sensor separately

Incident Light

Small angle scattering Incident Light

Large angle scattering

Figure 322 Schematic diagram of Laser diffraction when encountering different size of particles

127

Simply consider a sample containing spherical particles or droplets of same sizes

Airy Disk could be used as an example in order to interpret diffraction pattern As

can be seen in Figure 324 it consists of an innermost circle surrounding with a

series of concentric rings of decreasing intensity Also the profile of irradiance is

displayed with red wave patterns (Pan et al 2016)

The angular radius of the Airy disk pattern where from the peak of irradiance to the

first minimum is expressed with Equation 333 in the situation when using small

angle (sin 120579 cong 120579) (Pan et al 2016)

∆θ =122120582

119889333

Where ∆θ is the angular resolution 120582 is the wavelength 119889 is the diameter of

particles or droplets

II

(θ) II

(θ)

Sin

θ

Sin

θ

a b

Laser Light source

Sample with droplets

Diffracted image

Incident Light

Side scatter light sensor

Figure 324 Diffraction patterns and the corresponding radial intensity for two spherical particles 1 (a) and 2 (b) in different sizes

Figure 323 Schematic diagram of laser diffraction particle size analyser

128

Thus it is clearly to find that the size of Airy disk is directly proportional to the

wavelength λ and inversely proportional to the size of particle d In addition to that

Δθa which equals to 122 λd1 is smaller than Δθb which equals to 122 λd2

therefore 1198891 is larger than 1198892 indicating that the diffraction pattern of larger

particles is denser than that of smaller ones

A real sample contains droplets or particles of different sizes and may also in

different shapes thus the resulted diffraction pattern is overlapped by each specific

diffraction pattern and the generated intensity profile will be the sum of intensity

plot of each particle The particle analyser records this intensity plot as raw intensity

data and the distinguish individual diffraction patterns from the summed intensity

profile where this profile will be divided into different individual intensity plots

representing for groups of particles in similar size These groups are known as size

classes Theoretically calculated intensity profiles of every size classes using Mie

theory are compared to the experimental ones measured by instrument From

there the percentage of particles in specific size class namely particle or droplet

size distribution is obtained (Wriedt 2012)

As can be seen from Figure 325 droplet size distribution is plotted as the amount

of each size by volume (volume fraction) as the function of diameters also the

illustration of size classes consisting of representative droplets is presented

3632 Interpretation of particle size distribution

The interpretation of the result of droplet size distribution depends on the type of

measurement applied and the corresponding basis of calculation There are three

common distribution-based systems number distribution surface distribution and

Droplet size

Vo

lum

e d

ensi

ty (

)

Figure 325 Droplet size distribution of a sample and the corresponding illustration of size classes

129

volume distribution where a few of statistical parameters are calculated in order to

interpret droplet size distribution data (McClements and Coupland 1996)

Central values including mean median and mode are calculated for interpreting

the commonest droplet size in a sample Noticeability if the droplets size

distribution is a symmetric plot those central values are equivalent namely

mean=median=mode ldquoMeanrdquo refers to a calculated value of the average of droplet

sizes Depending on different distribution based systems including number

distribution surface distribution and volume distribution different definition and

corresponding calculation for mean value is generated such as number means

(eg D [10]) and moment means including surface area moment mean (D [32])

and volume or mass moment mean (eg D [43])

Surface area moment mean is called Sauter Mean Diameter (SMD) termed D [32]

It is calculated by involving both volume and surface area The definition of SMD

refers to the diameter of a sphere that has the same volume-to-surface ratio as a

target droplet or particle in particulate material thus it is also known as surface-

volume mean Equation 334 is applied for SMD calculation when the size

distribution is applied to characterize the material (Canu et al 2018)

D[32] =sum 119899119894119889119894

3119899119894=1

sum 1198991198941198891198942119899

119894=1

334

Where 119899119894 is the number of droplets in a size fraction and 119889119894 is the diameter of

droplets in this size fraction

In terms of the physical meaning SMD for a given droplet is formulated according

to Equations 335~337

D[32] = 11988932 =119889119907

3

1198891199042 335

119889119907 = (6119881119901

120587)

13

336

119889119904 = radic119860119901

120587337

Where 119889119907 is the volume diameter of droplet 119889119904 is the surface diameter of

droplet 119881119901 and 119860119901 represents for volume and surface area of droplet respectively

130



A particle size analyser Mastersizer 3000 (Malvern Instruments Ltd UK) was

applied equipping with Hydro EV which is a dip-in and semi-automated wet sample

dispersion unit which is illustrated in Figure 326 In this study a 500 mL laboratory

beaker was applied Physical diagram of the instrument is shown in Figure below

With an accuracy of plusmn06 this instrument is capable of measuring particle size

ranging from 10 nm to 35 mm

The dispersion unit is applied to circulate the sample through the cell where the

sample flow passes through the instrumentrsquos laser path Then the sample is

measured by optical unit using red and blue light wavelengths The optical unit is

the key component of the system which directs light through the sample and then

collect the diffracted light by the droplets Cell window is a key art of wet cell which

is the direct path of sample passing through Thus it has to be kept clean for a

desired result

1 Optical unit

2 Wet dispersion

unit

3 Wet cell

4 Computer running the master sizer application

software

Figure 326 Illustration of instrument Mastersizer 3000 connecting to the wet dispersion unit

131


a) Preparation for the test

For the measurement of sample taken from the hot mixture during preparation 3

mL of sample was pipetted out and transferred to 8 mL snap-cap specimen vials

filled with 2 mL hot water at 50degC After being well mixed 3 mL of mixture was

pipetted into the dispersion unit containing 500 mL pure degassed water which is

used as dispersant Slightly change of the amount of added sample in order to

ensure that the obscuration bar indicated in the system was in the right range

around 5 to 15

For the measurement of sample taken originally from prepared solid-like cream in

order to allow cream sample being homogenized stirring in dispersant unit and also

avoid lump of cream sample blocking wet cell and the flowing path treatment was

carried out before adding it into the dispersant beaker Half teaspoon amount of

cream which is nearly 2 g was added into a beaker Then some hot water heated

at around 50 degC was poured inside The mixture was homogenized using a stir and

heater where the temperature was set as 70 degC After the mixture was visually

observed to be homogenized 3 mL diluted sample was pipetted into the dispersion

unit containing 500 mL pure degassed water which is used as dispersant

Obscuration bar was monitored within 5 to 15 by changing the amount of

injected sample

Refractive index of the dispersant was quickly measured where a refractometer

was applied The refractive indexes of water and paraffin oils were determined

respectively The particle density of mixed paraffin oils was approximately

measured by weighing a specific volume v of mixed paraffin oils If the weight is

denoted as m the average particle density was estimated see Equation 338

(Singh 2002)

Particle density =119898119886119904119904 119900119891 119904119886119898119901119897119890

119907119900119897119906119898119890 119900119891 119904119886119898119901119897119890=

119898

119907338

Where v is the volume m is the mass

b) Experimental set-up

Before carrying out the measurement a standard operating procedure (SOP) was

preliminarily set up using software of the instrument and details of parameters are

listed in Table 319 The measurement was carried out following the induction from

the instrument

132

Table 319 Details for SOP applied in droplet size analysis for mimic cream

364 Microscopy

Sample of cream was examined under a polarized light microscope one day after

preparation under a magnification of x64 where The Axioplan 2 imaging

microscope was applied (Zeiss Germany) Samples were prepared by smearing

tiny amount of creams on to microscope slides with glass cover slips on top

365 Surface and Interfacial Tension Measurement

Surface activity was preliminary carried out on SLs using Du Nouumly ring method

where surface tension between SLs solution and air was analysed

3651 Theory

Liquid surface tension γ (N m-1) refers to a phenomenon caused by the unbalance

cohesive forces of molecules on the surface (between liquid and gas) or interface

(between two immiscible liquids) which is reflected in the tendency of fluid surface

to contract to the minimum Physically surface tension is defined as a tensile force

F per unit length L As illustrated in Figure 327 the dark blue bar has a tendency

Accessory (Hydro EV) Material (Mixed Paraffin Oils)

Dispersant (Water)

Stirrer Speed (rpm)

1500 Refractive Index 1466 Refractive index 133

Ultrasound Mode

None Particle Density 089

Analysis

Model General purpose Sensitivity Normal Scattering model Mie

Measurement Sequence

Number of measurement

5 Background measurement duration (redblue) (seconds)

10

Obscuration limits ()

01-20 Sample measurement duration (redblue) (seconds)

10

133

to be pulled towards left due to the surface tension and the force F is required to

balance it and increase the surface area (Hartland 2004)

The measurements of surface and interfacial tension for liquid are generally

classified into equilibrium methods such as du Nouy ring method Wilhelmy plate

method and pendent drop method and dynamic methods such as bubble

pressure (Hartland 2004) Besides due to the different measuring principle Nouy

ring and Wilhelmy plate methods are also known as force tensiometry where

pulling force is measured and related to the tension while pendent drop belongs

to optical tensiometry where the shape of drop is optically determined and related

to the tension In this project force tensiometry was applied

F

dx

L

Surface

Figure 327 Schematic diagram of force that applied to increase the surface area and the surface tension is proportional to this measured force

134



The Kruumlss K11 tensiometer (Kruumlss GmbH Germany) instrument was applied for

surface and interfacial tension measurement of SLs Figure 328 displayed photo

of physical model of the tensiometer

Du Nouumly ring method was applied The ring is made of platinum-iridium which has

high solid surface free energy and a contact angle of 0ordm is generally obtained

thereby realising superb wettability when contacting with liquid Based on Du Nouumly

theory the ring method measures the maximum pulling force Fmax on a ring by the

surface or interface Referring to Figure 329 when exerting a force on the fully

submersed ring to pull it out of liquid bulk through the phase boundary a lamellar

meniscus of liquid will be produced and lifted up to the maximum height then

eventually teared reflecting on the force firstly increasing to a top value followed

by a decrease after the lamella tears from the ring The measured maximum force

is related to the surface tension With the wetted length of ring of L = 2πR the

relationship between force 119865 and measured surface tension γ is expressed as

below see Equation 339 and 340 (Lee et al 2012)

119865 = 2γL cos 120579 = γ ∙ 4πR ∙ cos 120579 339

γ =119865

119871 cos 120579340

Figure 328 Physical model of tensiometer

135

Where L is the wetted length of ring F is the force γ is the surface tension θ is

the contact angle R is the inner radius of the ring

36522 Measuring Procedure for surface tension


08 mg 1 mg 184 mg 2 mg 28 mg 384 mg 54 mg 9 mg and 12 mg of SLs

were respectively weighed and certain amount of distilled water was used for

dissolution and added up to 40 ml for each of them Then prepared SLs solutions

with concentrations of 20 mg L-1 25 mg L-1 46 mg L-1 50 mg L-1 70 mg L-1 96 mg

L-1 135 mg L-1 225 mg L-1 and 300 mg L-1 (theoretical concentration) were stored

in 50 mL centrifuged tubes separately and ready for the measurement

The platinum-iridium ring has to be nearly perfect as small blemish or scratch can

greatly affect the accuracy of the results Thus the pre-treatment of ring was done

right before every single test When no solvent attached to the ring distilled water

was used for the cleaning where the ring was fully sprayed using the wash bottle

filled with distilled water If oily media was attached to the ring after the experiment

methanol was applied instead Then the wetted ring was dried with the help of

Bunsen burner Proper and moderate operation is required because no

overheated is allowed for maintaining the perfection of the ring

b) Experimental procedure setting

The experiment was done following the procedure as inducted Template of Du

Nouumly Ring (SFT) was selected as the measuring method for the surface tension

measurement where standard parameters are included and they are suitable for

most of common cases Among those parameters correction method was selected

Liquid

rin

g θ

L

F

Liquid

F

Lamella

ring

Figure 329 Schematic illustration of Du Nouumly ring method (left) and its cross-section view (right)

136

as Harkins amp Jordan and immersion depth was set as 3 mm The measurement

was started by selecting ldquoRun the measurementrdquo A measuring sequence guide

from the system was followed for the measurement

c) Experimental accessories cleaning

After every test glass sample vessels were filled with Decon 90 and rest for 2 h

after which they were fully cleaned with distilled water Only well cleaned vessels

could be used for the new sample The ring was cleaned after testing one type of

material which is submersed in a beaker filled with Decon90 and rest for 2 h Then

the ring was washed with distilled water and dried with Bunsen burner flame

366 Mass Spectrometry (MS) and Tandem Mass

Spectrometry (MS-MS)

Structural analysis was carried out for both of sophorolipids (SLs) and

Mannosylerythritol lipids (MELs) with the help of Mass Spectrometry technology

And further confirmation was made by applying tandem mass spectrometry and

liquid chromatography-mass spectrometry

3661 Theory

36611 Mass spectrometry (MS)

Mass spectrometry (MS) is a universally applied analytical technique for identifying

unknown compounds in a sample through converting neutral molecules in the

sample to rapidly moving ionized fragments using different ionisation method and

then charged particles are separated in to different populations based on their

masses Generally mass spectrometry process consists of four main stages which

are ionisation acceleration deflection and detection (Ruhaak et al 2018)

As Figure 330 illustrated where high vacuum system of spectrometer consisting

of ion source mass analyser and detector was displayed neutral molecules in the

vaporised sample will be initially ionised with the present of an ionization source

thereby converting to charged particles either positive or negative through

removing or absorbing of electrons After being accelerated when passing through

a set of charged parallel plates at different volts ions enter into the magnetic field

where ions are subjected to a sideway force and deflected based on their masses

and the charge on it Therefore mass-to-charge ratio denoted as mz is

introduced for combination of those two factors Referring to the diagram green

stream consisting of ions with greatest mz value deflected least while red stream

deflected the most which contains ions with the smallest mz Only those ions in

purple stream could eventually reach the detector and are quantified by ion counter

137

Others will be neutralised and pumped out of the spectrometer (McLafferty 2012)

After that those detected ions will be converted to the form of current and analysed

by the recorder presenting as a mass spectrum which is intensity or abundance

as a function of their mz

36612 Tandem mass spectrometry (MS-MS)

Based on the principle of mass spectrometry where sample molecules are ionized

to separate into charged fragments according to their mass-to-ratio value tandem

mass spectrometry refers to that the a second or more mass spectrometers are

coupled to the previous one thereby further breaking down selected ions into

smaller fragments The work system of MS-MS could be interpreted schematically

in Figure 331 where sample molecules are firstly ionised followed by mz

separation using mass spectrometer MS1 The red ion selected from MS1

represents for precursor ions which possess particular mz value which are

fragmented into smaller product ions These particles are transferred to the second

mass spectrometer MS2 for mz separation followed by detection and analysis

with the help of detector (Hiraoka 2013) As an outcome a mass spectrum is

obtained presenting as intensities of molecules upon corresponding mz values

Ion

source

Mass analyser Detecto

r

record

er

Ionisati

on

Accelerati

on

Deflectio

n

Detectio

n

electromagnet

vacuum

Vaporised sample

Figure 330 Schematic diagram of the theory of a mass spectrometry

138



The mass spectrometer (Waters UK) with electrospray ionisation (ESI) method

was used for MS and MS-MS measurements on SLs Negative ionisation mode is

selected and deprotonated molecules were expected to be observed in the mass

spectra Time of flight (TOF) detection was equipped Same mass spectrometer

was used for MS measurements on MELs where ESI was applied as ionisation

technique and TOF analyser was applied for the determination of mass-to-ratio

values of ions While positive ionisation mode was selected for MS analysis on

MELs thereby obtaining protonated or alkali adduct sample molecules Acetonitrile

was the solvent in mobile phase for the measurements


Samples of SLs and MELs were prepared for MS and MS-MS respectively A small

amount of extracted product which is nearly 50 mg was transferred from sample

bottle to a drying dish using a laboratory micro spatula Proper amount of ethyl

acetate was added into the drying dish for fully dissolve the product Then this

mixture was diluted 30 times with ethyl acetate followed by a filtration using 022

μm membrane The 1 μL filtered sample solution was stored in 2 mL glass sample

chromatography vials Five samples were prepared for each product

ioniser

sample

+

-

-

+ -

MS

1

- fragment

-

- - MS

2

detector

Ionisation mz separation

fragmentation

mz separation

detection

Figure 331 Schematic diagram of the theory of mass spectrometry

139

Chapter 4 Preliminary Characterisation of E45

Cream

Performance of E45 cream in terms of rheological properties droplet size

distribution and thermodynamic properties was preliminary studied The

conclusion could be used as a standard for the following mimic and bio cream

preparation

41 Rheological Characterisation of E45 cream

Dermatological E45 cream 350 g was purchased from The Boots Company PLC

(UK) which is packed in a jar on shelf Different rheological characterisations were

carried out for studying the flow property of E45 cream including steady state

shear and oscillatory sweep A controlled stress AR 2000 rheometer (TA

instrument) was applied equipped with cone and a 40 mm plate geometry with a

cone angle of 2deg All measurements were repeated at least twice at same

temperature condition This enabled a coefficient of variation of 5 in all cases for

making sure that highly reproducible date was obtained Before the measurement

the instrument was checked for proper function by measuring the viscosity of

silicon oil (Newtonian flow)

411 Preliminary Testing Conditioning Step Determination

In order to obtain a relatively accurate rheological behaviour and reproducible

results samples should get rid of history structures


The test introduced in this chapter was applied for seeking a proper stress for pre-

shear and a minimum equilibrium time before staring the experiment

41111 Pre-shear Stress Determination

The measurement was carried out following the procedure for pre-shear stress

determination

1 Check whether the air supply is sufficient for the rheological measurement

where the pressure should be no less than 30 psi

2 Turn on the water supply which is a water bath

3 Power on the Rheometer and access the rheology software on the

computer

140

4 Inertia calibration and bearing friction correction Instrument inertia was

firstly calibrated following the induction in the software which is expected

in the range of 14-16 microNms2 Then the cone-plate geometry was attach to

the rheometer followed by a geometry calibration After that go to the

InstrumentgtMiscellaneous page and carry out bearing friction calibration

where a value between 05 and 11 microNm (rad s-1)-1 is accepted

5 Perform rotational mapping

6 Set the zero gap following the software induction which is set to be 57mm

in the test After that raise the head up and load the sample with correct

filling

7 Lower down the head to reach zero gap Then select Peltier Plate system

for temperature control

8 Create a new procedure as the test program where steady state flow was

selected for the test Input parameters in the procedure which is specified

in Table 41 Then start the test


9 After the measurement finish raise the head up and remove the measuring

geometry Clean the plate and cone

10 Exit the software and export date Then power off the rheometer and the

water bath

41112 Equilibrium Time Determination

Oscillatory time sweep (OTS) test was carried out to determine minimum time for

the structure of E45 cream to reach steady state after loading where E45 cream

was swept under constant oscillatory stress and frequency during certain time slot

Before this oscillatory stress sweep (OSS) test was carried out in order to obtain

a proper controlled variable (oscillatory stress) that could be used in OTS test to

Conditioning Step

Temperature (degC) 25

Equilibrium time (min) 0

Pre-Shear No

Steady State Shear Step

Variables Shear stress (Pa) 10-500

Number of Points 10 points per decade in log mode

141

make sure the test was carried out within linear viscoelastic region (LVER) The

procedure was introduced as follow

1 Follow step 1 to 4 described in chapter 41111 for pre-shear stress

determination test

2 Perform oscillatory mapping

3 Set the zero gap following of 57mm in the test After that raise the head up

and load the sample with correct filling



5 Create an oscillatory stress sweep procedure as the test program Input

parameters in the procedure which is specified in Table 42 Then start the

test

Table 42 Parameters for preliminary linear viscoelastic range (LVER) determination for E45 cream characterisation

Conditioning Step



Pre-Shear No

Oscillatory Stress Sweep Step

Variables Oscillatory stress (Pa) 001-1000

Controlled variable 1 Hz


From the result of OSS test an oscillatory stress of 4 Pa was selected for the

following OTS test (Result will be introduced in chapter 4112) Then the OTS test

program was create for E45 cream following procedure steps described below In

addition pre-shear was performed in conditioning step where stress was

determined as 50 Pa (Result will be introduced in 4112)

1 Follow step 1 to 4 described in chapter 41111 for LVER determination

test

2 Create an oscillatory time sweep procedure Input parameters in the

procedure which is specified in Table 43 Then start the test



142


water bath


Conditioning Step

Temperature (degC ) 25


Pre-Shear Yes Shear stress (Pa)

60 Duration (min)

5

Oscillatory Time Sweep Step

Controlled variable

Oscillatory stress (Pa) 4

Frequency (Hz) 1

Time Duration (min) 30 70 100 had been applied separately

Sampling Time (second) 5

4112 Results and Analysis

Pre-shear stress determination

A representative result of steady state shear that carried out on E45 cream without

any pre-shear and equilibration was presented in Figure 41 E45 cream presented

shear thinning behaviour where the apparent viscosity decrease with increasing

shear stress In addition 1st Newtonian plateau (purple dash line) shear thinning

(red dash line) and 2nd Newtonian plateau (orange dash line) presented in the flow

profile of E45 This preliminary shear test was carried out for determination of the

stress applied during pre-shear Selection of the value should lie beyond the 1st

Newtonian plateau but not way too large in order to ensure rebuilt structure

Therefore referring to the viscosity behaviour presented in rheogram shear stress

could be a value selected from 30 to 60 Pa which is determined to be 50 Pa

The 1st Newtonian plateau could refer to the resistance of microstructure to the

external shear force due to the presence of yield stress where the apparent

viscosity showed independent with shear stress and no obvious flow or

deformation was witnessed when the wall depletion effect is eliminated or

neglected However for highly concentrated dispersions with large droplets that

confined in a gap contacting with smooth surface wall slip usually occurred due to

the displacement of the disperse phase away from solid boundaries (Barnes 1995)

143

where the overall deformation of the material is localized in a thin layer of thickness

adjacent to the confining walls resulting in a large velocity gradient at the wall

Thus the actual deformation experienced by material is highly different from the

effective shear rate that applied resulting in an underestimation of the actual

viscosity (Mukherjee et al 2017) As indicated that wall depletion mostly affects

yield stress and sometimes apparent viscosity at 1st Newtonian plateau namely

resulting in lower yield stress which is approximately 65 lower compared to the

actual value for a hand lotion (Saarinen et al 2014) The reason for the

phenomena may be steric hydrodynamic viscoelastic and chemical forces and

constraints acting on the disperse phase immediately adjacent to the walls

(Hatzikiriakos 2012)

However in this study rheological characterisations of all creams were conducted

using the same smooth cone and plate geometry and confined within the gap of

57 mm plus their nature which are semisolid systems with large size droplets

dispersed and no measures have been taken to inhibit wall depletion phenomenon

thus without carrying out further investigations for detecting whether a wall

depletion existed or the effect degree of this phenomenon it has to point out that

wall slip phenomenon may occur as it is a common phenomenon for most complex

materials Even though as all rheological measurements are consistently carried

out in terms of geometry gap and other measuring parameters also reduplicative

results were obtained for every single cream thus the rheological data that

01

1

10

100

1000

10000

100000

1000000

10 100 1000

Vis

cosi

ty

Pa

S

Shear Stress Pa

Figure 41 Exploratory flow characterisation of E45 cream for pre shear stress determination where viscosity varied as a function of shear stress

144

measured could be utilized as qualitative indices for comparing the relative

differences between creams

Equilibrium time determination

Linear viscoelastic range (LVER) where storage modulus and loose modulus are

independent with applied stress was determined by carrying out oscillatory

amplitude sweep for the following dynamic measurements As a result change of

storage modulus Grsquo and loss modulus Grsquorsquo of E45 cream as a function of oscillatory

stress was obtained in rheogram presented in Figure 42 Grsquo and Grsquorsquo kept constant

until the applied stress increased to around 10 Pa and Grsquo was always over Grsquorsquo

during this range where is known as LVER Afterwards both of Grsquo and Grsquorsquo started

to decrease When applying oscillatory stress of over 50 Pa Grsquorsquo was predominant

in the system indicating a viscous behaviour dominated system An oscillatory

stress of 4 Pa was selected for the following oscillatory time sweep

Oscillatory time sweep of E45 cream was carried out after pre shearing cream

sample at 50 Pa for 5 minutes As an output of oscillatory time sweep E45 cream

was swept under constant amplitude and frequency for a period of time where

changes of storage modulus Grsquo and loss modulus Grsquo were recorded As seen in

Figure 43 Grsquo and Grsquorsquo began to level off roughly after 50 min of sweep and they

tend to reach plateau until 100 min

1

10

100

1000

10000

01 1 10 100

GG

P

a

Osc Stress Pa

G

G

Figure 42 Oscillatory amplitude sweep of E45 cream for determination of oscillatory stress within linear viscoelastic range

145

However equilibrating cream for completely rebuilding the structure also has

drawbacks Too long time equilibration may cause water evaporation of E45 cream

thereby bringing edge effect which happens on the boundary of sensory system

when the measurement is running The large effect may cause extra shear strain

to be recorded by the measuring system then inaccurate higher viscosity of cream

will be measured as a result In another aspect the edge cracking may lead to

discontinuity of shear rate happen in viscous emulsions and gel dispersions Under

this circumstance part of sample was edged out by the geometry (cone here)

Subsequently for the remaining cream sample portion of which rotates with the

movement of boundary portion of which may rotate at the same speed as the

boundary does And those in the centre of geometry do not behave with a

consistent velocity gradient Thus for a compromise 55 min was selected as the

applicable equilibrium time for E45 structure built up

4113 Conclusions of Preliminary Testing

As a result a pre shear step was set up where E45 would be sheared at 50 Pa for

5 min followed by an equilibration for 55 min Rheological measurements were

carried out in this chapter just for setting up conditioning step for the following

experiments so they may not truly interpret the rheological behaviour of E45 cream

100

1000

10000

100000

0 20 40 60 80 100 120 140

G

G

Pa

Time min

G

G


146

412 Rheological Characterisation on E45 Cream

In this chapter standard rheological tests which were carried out after previously

determined conditioning step were introduced


41211 Steady State Shear

Steady state shear (SSS) test was performed to investigate shear dependent non-

Newtonian flow behaviour of E45 cream By spinning the cone geometry to shear

the cream on a stationary lower plate with increased shear stress the apparent

viscosity was obtained as a function of applied shear stress The procedure of SSS

test for pre-shear stress determination described in chapter 41111 and the

parameter input in this SSS procedure was specified in Table 44 After the

measurement sample left on geometry and the Pelite plate was cleaned and water

bath was turned off The instrument was powered off after use

Table 44 Parameters for steady state shear test on E45 cream

41212 Continuous Shear Stress Ramp (up and down)

The continuous ramp test was applied in order to study the thixotropic property of

E45 cream where the shear stress increased from 10 Pa to 150 Pa during ramping

up and then reduced to its original value of 10 Pa during ramping down step The

procedure of calibration zero gap setting and mapping could be referred to chapter

41111 The created measurement program was specified in Table 45

Conditioning Step




50 Duration (min)

5




147

Table 45 Parameters for continuous shear stress ramp test on E45 cream

Conditioning Step




50 Duration (min)

5


Ramp up Variables Shear stress (Pa)

10-150

Ramp down Variables Shear stress (Pa)

150-10


41213 Dynamic Oscillatory Stress Sweep

The accuracy of previous obtained LVER of E45 cream was further confirmed by

conducting a new dynamic oscillatory stress sweep (OSS) after a pre-shear step

The procedure could refer to chapter 41111 and parameters are specified in

Table 46

Table 46 Parameters for new linear viscoelastic range (LVER) determination for E45 cream characterisation

Conditioning Step




50 Duration (min)

5





41214 Dynamic Oscillatory Frequency Sweep

The analysis of time-dependent non-Newtonian flow behaviour of E45 cream was

conducted using dynamic frequency sweep (OFS) measurement The procedure

of calibration zero gap setting and mapping in the measurement procedure were

148

introduced in chapter 41111 Then an oscillatory frequency sweep program was

created and parameter inputs are specified in Table 47 The amplitude which is

the oscillatory stress was controlled at 4 Pa (the result from new OSS

measurement)

Table 47 Parameters for oscillatory frequency sweep on E45 cream

Conditioning Step




50 Duration (min)

5


Variables Oscillatory frequency (Hz) 001-1000

Controlled variable Oscillatory stress (Pa) 4



Rheological behaviour of E45 cream under steady state shear

Viscosity profile of E45 cream was eventually achieved by carrying out rotational

shear test on E45 cream after pre-shear for removing history structure and

equilibrium for realizing zero shear condition Apparently from Figure 44 viscosity

of E45 cream presents an overall decrease trend with the increased shear stress

ranging from 10 Pa to 300 Pa which indicating a shear thinning behaviour of flow

When the shear stress was lower than 40 Pa viscosity of E45 cream kept constant

at approximately 3times105 Pamiddots After exceeding a yield stress it started to decrease

When applied shear stress was over 50 Pa a dramatically sharp drop of viscosity

within a small stress range (50-60 Pa) was witnessed indicating the shear thinning

behaviour The 2nd Newtonian plateau refers to a gradual decrease of viscosity with

the shear stress over 60 Pa

As stated previously in the preliminary test for E45 characterisation wall slip may

happen in this situation leading to an inaccurate interpretation of E45 rheological

behaviour Also researchers pointed out that wall slip usually manifests itself

giving lower viscosity and lower yield stress when changing to a smaller sized

geometry or sudden breaks witnessed in flow curves especially for those

149

dispersions consisting of large droplets coupled with smooth surface and low flow

dimensions (Saarinen et al 2014) Thus in this report the following analysis in

respect to rheological measurements are specified that a 40 mm cone and plate

geometry was consistently applied with a measuring gap of 57 mm for all creams

In addition to that maximum viscosity of E45 that characterised in this project was

approximately 105 Pamiddots which is similar to that obtained from a study where a

limiting viscosity for a cream was more than 104 and the values of yield stress were

reasonable which line in between 10 Pa and 100 Pa (Kwak et al 2015)

Viscosity profile which illustrates the flow and deformation of E45 cream when

subjecting to external shear macroscopically reveals microstructure change of the

system During lower shear stress range (below 40 Pa) the presence of 1st

Newtonian plateau reflects the stable three-dimensional gel structure or matrix of

E45 cream was formed by interacting forces between droplets which is strong

enough to support cream and resist the external force In addition carbomer a

high-molecular polymer is used as thickener in the formula of E45 The cross-

linking of polymer chains also contributes to the structural network (Siemes et al

2018) Continuously increasing the external stress microstructure of cream

gradually rearranged where the aggregated structures droplets and polymer

chains began to break down deform and disentangle thus presenting as a

decrease trend of viscosity (Garciacutea et al 2018) As the arrangement of droplets

001

010

100

1000

10000

100000

1000000

10000000

100000000

10 100 1000

Vis

cosi

ty P

a∙S

shear stress Pa

Figure 44 Steady state shear test on E45 cream where viscosity varied as a function of shear stress ranging from 10 Pa to 300 Pa

150

completely aligned with the flow shear thinning behaviour was witnessed which

enables the application of cream product to skin

Normally shear thinning behaviour will happen after the shear stress exceeds a

yield value which is known as yield stress τF With the definition of flow onset for

yield stress the value is determined from the maximum of viscosity profile ηmax

from some literatures (Choi et al 2015) While regarding to the flow curve of E45

cream it is easier to define τF as the end of 1st Newtonian plateau In the study of

primary skin feeling test some researchers correlated that with yield stress

indicating that a cream needed a higher shear stress to flow will be rated higher in

terms of spreadability This information for E45 cream was recorded for further

comparing with lab-made mimic creams

2nd Newtonian plateau started when the viscosity decreased to 10-1 Pas at shear

stress of 300 Pa which is usually correlated to the secondary skin feeling that is

the cream is expected to show a low viscosity during high shear stress or shear

rate range for achieving a better absorption capacity perceptible on the skin after

application and the end-of-use feeling (Kwak et al 2015) A suggested shear rate

γ for this assessment is 500 s-1 which corresponds to a shear stress of nearly 300

Pa for E45 cream Thus for E45 cream the viscosity of less than 01 Pas at high

shear rate γ = 500 sminus1 was displayed which is similar to the test creams with

decent secondary skin feeling (viscosity of 002~04 Pas at shear rate γ = 500 sminus1)

in the project of Bekker et al (Bekker et al 2013) The step decrease (break in

curve) is witnessed in 2nd Newtonian plateau for all viscosity curves of E45 The

microstructure variations may contribute to this phenomenon among which the re-

entanglement of polymer molecules of carbomer supplied the most

Thixotropic property of E45 cream

Thixotropic property refers to the time-dependent shear thinning behaviour where

a material exhibits decrease of viscosity or shear stress under constant shear rate

over time In addition thixotropic behaviour holds the responsibility for not

achieving microscopic reversibility of the stress-strain rate plot therefore resulting

a hysteresis loop (Petrovic et al 2010) Referring to the hysteresis loop test of E45

illustrated in Figure 45 ramp up step illustrated its shear tinning behaviour where

the decay of viscosity with increasing the shear rate while the backward trend of

ramp down descending process does not retrace the original path where the

structure gradually recovered and rebuilt Therefore a hysteresis loop is formed

as seen in the rheogram the area of which indicates the degree of thixotropy and

151

the energy required to break down this thixotropic structure Besides the yield

stress τF of 5412 Pa could be obviously acquired from the stress-rate curve

which is similar to that obtained in previous steady state shear measurement

Rheological behaviour of E45 cream under oscillatory sweep

A modified oscillatory amplitude sweep was carried out on E45 where the sample

was pre sheared and equilibrium for a certain time in order to obtain a reliable

LVER range The result did not present large different from the preliminary one

displaying a LVER range from 01 to 10 Pa during which storage modulus and

loose modulus were independent with oscillatory stress (result not shown in

diagram) Thus the oscillatory of 4 Pa could be applied as the critical strain for the

following oscillatory frequency sweep

Dynamic oscillatory test is a common way for investigating the viscoelastic

properties of materials As for E45 cream when subjecting to a constant oscillatory

stress the change of storage modulus Grsquo and loss modulus Grsquorsquo were recorded as

a function of angular frequency the result of which is presented in the log mode

rheogram (Figure 46) Grsquo and Grsquorsquo of E45 cream exhibited a qualitatively similar

behaviour over the measured frequency range nearly independent of frequency

which agrees with the results for cream-like products (Sanz et al 2017) Also

storage modulus Grsquo is always greater than loss modulus Grsquorsquo during this frequency

range indicating a structured solid domain system of E45 cream However during

(380E-04 5412)

0

40

80

120

160

0 100 200 300 400 500

Sh

ear S

tress

P

a

Shear Rate s⁻sup1

Ramp Up

Ramp Down

Figure 45 Shear ramp test on E45 cream for determination of hysteresis loop where shear stress ramped up and down as a function of shear rate

152

lower frequency range where longer period (duration of time) of one cycle applied

Grsquo and Grsquorsquo presented a tendency of meeting together In another words E45 cream

may present like a liquid viscoelastic material at low frequencies

Modulus as a function of frequency could be a sound explanation for interpreting

the microstructure of a viscoelastic material when the amplitude applied is

confined in LVER This is normally known as small amplitude oscillatory sweep

(SAOS) where the moduli are only dependent on frequency but not the strain or

stress (Luan et al 2017) As for E45 cream the SAOS result presented a well-

structured gelled system In additions to the strong gel phase formed by the

interaction between water and bilayers of fatty amphiphiles and anionic surfactants

the support from entangled long chain polymer (carbomer) also contribute to

maintain the structure against external force

42 Droplet Size Distribution (DSD) Analysis

Droplet size distribution of E45 cream was studied using Mastersizer 3000

(Malvern Instruemnts Ltd UK) combined with a wet sample dispersion unit Hydro

EV


Solid state E45 cream was treated before the experiment The preparation

procedure could refer to chapter 36332 introducing measuring procedure of

10

100

1000

10000

001 01 1 10 100 1000

G

G

P

a

angfrequency rad s⁻sup1

G

G

Figure 46 Oscillatory frequency sweep on E45 cream where Grsquo and Grsquorsquo varied as function of angular frequency from 001 rad s-1 to 1000 rad s-1 at controlled oscillatory

stress of 4 Pa

153

preparation for solid-like cream sample Specified for E45 cream the

measurement procedure was carried out as follow

1 Half teaspoon amount of E 45cream nearly 2 g was added into a beaker

followed by adding hot water at around 50degC The mixture was

homogenized using a stir and heater where the temperature was set as

70degC This is recorded as sample A Sample B was prepared by adding 2

of SLES in sample A followed by a well mixing They were characterised

in terms of droplet size distribution separately by the same measuring

procedure

2 Meanwhile power on Mastersizer 3000 and open the software Instrument

cell cleaning was carried out regularly so there is no need to do this step

every time before test unless as required

3 Set up a new SOP (standard operation procedure) for E45 cream

measurement Details of important parameter settings are displayed in

Table 48 Refractive index of material was measured as mixed paraffin oils

as they are specified in the recipe of E45

Table 48 Details of SOP applied in droplet size analysis for E45 Cream


Dispersant (Water)

Stirrer Speed (rpm)

1500 Refractive Index

1466 Refractive index

133

Ultrasound Mode None Particle Density

089

Analysis

Model General purpose

Sensitivity Normal Scattering model

Mie




10


01-20

Sample measurement duration (redblue) (seconds)

10

154

4 After the mixture was visually observed to be homogenized 3mL diluted

sample was pipetted into the dispersion unit containing 500 mL pure

degassed water which is used as dispersant

5 Then start the measurement follow the procedure induction of the software

While measuring obscuration bar was monitored within 5 to 15 by

changing the amount of injected sample

6 When finished a cleaning step as default in the software was carried out

by following the induction Power off the instrument after use

422 Results and Conclusions

The volume density of droplets was measured as a function of corresponding

droplet size as a result of droplet size distribution test Sample A that prepared by

homogenized dissolving E45 cream in hot water before the test the DSD of which

is presented in Figure 47 in red curve It can be concluded that droplets of E45

presents a bimodal distribution but based on the calculation of accumulative

volume density that nearly 8685 (vv) of droplets were sized between 112 to 272

microm and less than 13 (vv) small droplets with sizes below 10 microm Besides the

maximum of the curve corresponds to the largest population of droplets with

diameter of 518 microm and the narrow distribution of the larger modal indicated that

most droplets in E45 cream are in equal size

112 08

518 72

272 0

0

2

4

6

8

001 01 1 10 100 1000 10000

volu

me

den

sity

droplet size um

E45 without sles

E45 cream+2SLES

Figure 47 Comparison of the droplet size distribution curves between sample A of pre-treated E45 cream and sample B of pre-treated E45 cream with additional 2wt of

SLES

155

Sample B was made by adding 2 of SELS in sample A followed by a well mixing

which presents a completely different mode of distribution compared to that of

sample A This value can only be applied as a qualitative indicator for the following

research as E45 was purchased from the store instead of freshly made

flocculation or aggregation may occur in the system leading to an inaccurate

exhibition of the microstructure As can be seen from the blue curve of DSD for

sample B adding 2 of SLES caused a shift to smaller droplet diameters and

broaden the size distribution And a multimodal mode was detected As suggested

from other study that an increase in the large size droplets reveals that the

interactions between flocculated oil droplets are sufficiently strong andor

coalescence has occurred (Perlekar et al 2012) Thus in a reversed way 2 of

SLES in the sample may cause deflocculating of oil droplets in E45 cream

resulting in average smaller droplets but an unstable system with a broader droplet

distribution

43 Differential Scanning Calorimetry (DSC) Analysis

Thermodynamic property of E45 cream was analysed with the help of differential

scanning calorimetry (DSC) measurement where TzeroTM DSC 2500 system (TA

Instrument) was applied


Measuring procedure for E45 cream could refer to chapter 3622 introducing

preparation procedure of DSC measurement on mimic creams The specific

measurement step for E45 cream is present as below

1 Weigh 5-10 mg of E45 cream into the alumina pan (pre-weighed with

lid) and record data followed by hermetically sealed with lid using Tzero

sample encapsulation press kit This is used as sample cell

2 Seal another empty alumina pan with lid using the press kit This is used

as reference cell

3 Power on the instrument and check the availability of nitrogen supply

Then open the TRIOS software Input required parameters including

pan weight and sample weight Select Autosampler mode

4 A scanning method was preliminarily created for E45 cream

(1) Ramp up Heating up E45 sample from -30 degC to 100 degC at a

constant heating rate of 5 ordmC min-1

156

(2) Isothermal Take an equilibration step where the sample was

isothermal at 100degC for 3 minutes

(3) Ramp down Cool down the sample from 100degC to the start point

which is -30 degC with the cooling rate of 5 ordmC min-1

(4) Isothermal Equilibrate the sample at 20 degC for 3 minutes

(5) Mark the cycle


507 mg sample of E45 was prepared weighed for the DSC test the thermogram

is displayed as in Figure 48 As can be seen the ice-melting peak was found

around zero degree centigrade and another transition witnessed during

endothermal period was at temperature around 55 degC Also sample degradation

was found when heating over 90 degC this may also because the instrument

malpractice During cooling a crystallisation point was found nearly 20 degC

44 Summary of Chapter 4

Commercialized E45 cream was characterised in terms of flow property droplet

size distribution and thermal properties aiming to provide a guidance for the

following preparation of mimic creams When using 40 mm cone and plate

geometry E45 was confined to a gap of 57 mm for rheological measurements

presenting shear thinning behaviour subjecting to increased shear stress and

showing an apparent viscosity of 3times105 Pamiddots with a yield stress of approximate 50

Pa A solid domain viscoelastic behaviour was observed with the help of oscillatory

Figure 48 DSC thermogram of E45 cream (screen shot directly from the software)

157

frequency sweep No GrsquoGrsquorsquo crossover point is witnessed in SAOS reveals that no

frequency-invariant solid-to-liquid transition happened within the measuring range

and it probably happens when the cream subjecting to larger amplitude or longer

period of oscillating A bimodal mode of droplet size distribution was witnessed

with droplets ranging from 10 microm to 100 microm with a narrow mode presenting a

relatively stable system in spite of possibility of flocculation of droplets during its

shelf life As for DSC result no obvious transition was witnessed only a melting

point was witnessed at around 55 degC Mimic creams were then prepared using key

components in the formulation of E45 cream including white soft paraffin light

liquid paraffin cetyl alcohol (CA) and glycerol monostearate (GM) incorporating

with lab-available sodium lauryl ether sulfate (SLES)

158

Chapter 5 Variation of Mimic Creams Prepared

with Different Emulsifying System

Characterisations of E45 cream in terms of its flow and thermal properties were

carried out and introduced in previous chapter where a standard rheological

behaviour of cream-like products were achieved giving reference for the following

mimic cream preparation and analysis Formulating mimic creams with different

concentrations of surfactant systems incorporating mixed paraffin oils in water will

be introduced in this chapter then desired formulations were determined in terms

of their rheological behaviours and thermodynamic properties when comparing to

standard E45 cream

51 Explorer Formulation of Mimic Creams

511 First Trial of Cream Formulation without Sodium Lauryl

Ether Sulfate (SLES) Using a Homogenizer

In the first trial of cream preparation only cetyl alcohol (CA) was applied as

surfactant for emulsifying mixed paraffin oils in water However as visually

observed from the appearance of the product (Figure 51) a heterogeneous

mixture was displayed where two phase were separated

A homogenised product with smooth texture in appearance is the preliminary

requirement for the preparation of a desired cream Thus it could be deducted from

the failure of this trial that only applying one type of fatty alcohol cetyl alcohol

(C16) in this mixed paraffin oils with water system is unable to realize expected

emulsifying effect Ionic or anionic surfactants were considered to be applied as

collaboration with fatty alcohol for achieving better emulsification (Terescenco et

Figure 51 Appearance of mimic cream prepared in the first trial using CA as the sole surfactant and a homogenizer for mixing

159

al 2018b) Another potential problem that led the production to failure could be

the selection of mixing unit Although homogenizer provided strong turbulence and

high speed of shearing for preparing ultrafine emulsions the efficiency was greatly

reduced by the contrast large size of vessel and its limited bulk mixing function

Therefore the homogenizer that used was unable to fully break down the oil phase

and water phase into small droplets for the following emulsification and stabilisation

by surfactants and emulsifiers

512 Second Trial of Cream Formulation with Sodium Lauryl

Ether Sulfate (SLES) Using an Overhead Stirrer

Based on the first trial of preparation in addition to cetyl alcohol (CA) SLES was

applied in the emulsifying system which is added in the aqueous phase An

overhead stirrer was applied equipped with a pitched blade turbine with six blades

as the impeller resulting axial flow while the rotation

Visually observed from the appearance of prepared product shown in Figure 52

a smooth and rich texture cream with a certain degree of firmness was obtained

However compared to commercial E45 cream the prepared mimic cream was

witnessed to be thinner and easier to flow

A steady state shear was carried on the mimic cream in order to get a general idea

about its rheological property After pre-sheared under 70 Pa for 5 min followed by

an equilibrium of 55 minutes the mimic cream was sheared from 10 Pa to 300 Pa

resulting a viscosity profile as a function of shear stress The Ostwald curve was

obtained where three stages are displayed in the profile The viscosity showed

independence with low shear stress then behaved shear thinning property after

exceeding the yield stress followed by a gradually decrease in the 2nd Newtonian

Figure 52 Appearance of mimic cream prepared in the second trial using CA and SLES as surfactants and a stirrer with pitched blade turbine for mixing

160

plateau The comparison is schematically presented in Figure 53 with

representative rheological curve of E45 and mimic cream

Green line and purple line with dot represented for the 1st Newtonian Plateau for

mimic cream and E45 cram separately where the average viscosities of them were

in the same magnitude indicating similar rigidity of mimic cream and E45 when at

rest Both of mimic cream and E45 presented sharply drop of viscosity within short

shear stress range when exceeding a certain yield stress showing shear thinning

behaviour The comparable data between E45 and mimic cream was summarised

in Table 51

Shear stresses at the end of 1st Newtonian Plateau for mimic cream and E45 were

2506 Pa and 2738 Pa respectively which are similar however a transition region

between this point and the start of plunge for mimic cream was apparently longer

than that for E45 cream Thus compared to E45 cream more stress was required

for spreading out the mimic cream to the skin In addition to that mimic cream

failed to reach as low viscosity during higher shear stress range as the E45 cream

showing a poor end-of-use in terms of absorption capacity perceptible on skin

Comparison data was summarised in table

513 814E+04

2738 365E+05

7924 219E+04

2506 187E+05

01

1

10

100

1000

10000

100000

1000000

1 10 100 1000

Vis

cosi

ty

Pa

S

Shear Stress Pa

E45

1st Newtonian Plateau ofE45

mimic cream

1st Newtonian Plateau ofmimic cream

Figure 53 Comparison of representative flow behaviour between E45 cream and mimic cream that emulsified by SLES and cetyl alcohol where viscosity varied as a

function of shear stress ranging from 5 Pa to 300 Pa

161

Table 51 Results of steady state shear measurement for E45 and mimic cream containing SLES and CA

Product

Shear stress at end of 1st Newtonian Plateau (Pa)

Average viscosity at 1st Newtonian Plateau (Pamiddots)

Shear stress at onset of plunge (Pa)

Dynamic viscosity at shear stress of 300 Pa (Pamiddots)

E45 cream 2738 3288times105 5130 lt0211

Mimic cream containing SLES and CA

2506 1704times105 7924 0407

As a conclusion the preliminary prepared mimic cream presents decent property

in terms of rheological behaviour under steady state shear compared to E45

cream Also SLES as an ionic surfactant is vital in the emulsifying system for

complete the preparation of cream product without which agglomerates were

separated out (Kumari et al 2018)

52 Formulation_Ⅰ of Cream Formulation Using a

Simplified Configuration

521 Appearance of Mimic Creams in Formulation_Ⅰ

After the preparation creams were transferred into 50 ml wide-opened jars where

they were rested for 20 min before subjecting to rheological tests Appearances of

prepared creams were presented in Figure 54 where the corresponding weight

concentrations of surfactants were specified Three components that involved in

the emulsifying system sodium laureth sulfate (SLES) cetyl alcohol (CA) and

glycerol monostearate (GM) was classified as anionic surfactant (SLES) and fatty

alcohols (CA and GM) In order to be simplified a nomenclature was created to

correlate surfactant components with their weight concentrations that is cream

containing [SLES CA GM] with the weight concentration wt of [xxx] For

example cream [066] refers to the cream containing 0 wt of SLES 6 wt of

cetyl alcohol (CA) and 6 wt of glycerol monostearate (GM)

Visually observing the appearance of creams after preparation those containing

no SLES displaying separated phases were identified to be failed preparation

which is shown on orange background This further proved the result obtained in

the second trial of preparation It is noticeable however that higher concentration

162

of fatty alcohols (CA and GM) led to the conversion of small agglomerates to a

larger lump and less water separated out

The presence of appropriate consistency and texture is the fundamental of a semi-

solid cream Mimic creams showed on purple background were visually

determined to be desired cream products especially those formulated with CA-to-

GM ration of 31 where 6 wt CA and 2 wt GM applied are desired namely

cream [262] [462] and [662] exhibiting smooth texture and seemly reasonable

rigidity Increasing the concentration of fatty alcohols creams with 6 wt CA and

6 wt GM were obtained (red background) These over-stiff products contained

crystals that were separated out On the contrary reduce the fatty alcohols in the

system had a tendency to result in fluid products with undesired low consistency

Referring to creams formulated with 2 wt CA and 2 wt GM they were very thin

and also bubbles were involved Thus as preliminary deducted that gel structure

was not fully established during cooling due to the lack of fatty alcohols (Deyab

2019) Further rheological measurements will be applied to give the evidence and

explanation

SLES wt CA (wt)

GM (wt)

0 2 4 6

6 6

6 2

2 6

2 2

Figure 54 Appearances of mimic creams prepared in Formulation_Ⅰ

163

522 Rheological Characterisation of Mimic Creams in

Formulation_Ⅰ

Rheological measurements allow to translate the qualitative properties of skin feel

to quantitative evaluation of how the material responds to stress and strain (Bekker

et al 2013) Mimic creams were analysed with different types of measurements

including steady state shear for viscosity profile analysis and dynamic oscillatory

for viscoelastic property investigation Creep test was also conducted as the

additional information for viscoelasticity evaluation


After rest in the storing jar for 20 minutes mimic creams were analysed using

AR2000 rheometer for the study of their flow properties using 40 mm cone and

plate geometry Proper amount of cream sample was confined in the measuring

gap of 57 mm followed by another equilibrium for 20 min before carrying out steady

state shear measurement Also the equilibrium time was proved to be reasonable

for sample to relax as highly reproducible data was achieved Figure 55 illustrated

flow properties of 12 creams which were allocated into four groups where their

viscosities change dependent on shear stress from 5 Pa to 300 Pa at 25 degC was

obtained

It has been suggested in the literature that if yield stress exists the typical steady

state shear viscosity curve for an emulsion presented in logarithm scale is roughly

divided into three stages 1st Newtonian plateau where viscosity is constant at low

shear stress shear thinning as shear stress increase 2nd Newtonian plateau where

the sample undergo high shear stress This is known as Ostwald curve (Blanco-

Diacuteaz et al 2018 Graziano et al 1979) A three-dimensional gel structure or matrix

that established in the semisolid system was witnessed according to 1st Newtonian

plateau where the cream remain its body and behaves like solid under small shear

forces such as product on shelf or during transportation (Blanco-Diacuteaz et al 2018)

With the shear stress increasing by different processes such as mechanical mixing

pumping or rubbing until the critical stress level is exceeded the matrix structure

will be destroyed where the viscosity drops dramatically and the cream body

becomes thinner and easier to flow This critical stress is generally defined as yield

stress Continuously increasing the shear stress leads to the cream with lower

164

viscosity behaving like fluidic emulsion state which is presented as the gradually

decrease of viscosity in 2nd Newtonian plateau (Moresi et al 2001)

Parallel compared between four rheograms only when the combination of 6 wt

cetyl alcohol (CA) and 6 wt glycerol monostearate (GM) (cream [x 6 6]) or that

of 6 wt CA and 2 wt GM (cream [x 6 2]) formulated in the emulsifying system

viscosity profiles behaved following Ostwald curve When 6 wt CA and 6 wt

GM involved in the system change of SLES concentration from 2 wt to 6 wt

had little effect on flow properties of creams in terms of average viscosity of 1times106

Pamiddots at 1st Newtonian plateau yield stress of over 100 Pa and shear thinning

behaviour Many literatures explained the reason for the presence of yield stress

in emulsion products some of which ascribed it to the formation of three-

dimensional network structure by the involvement of some polymeric thickening

agent or stabilizers (Oppong et al 2006 Nelson and Ewoldt 2017) As for the

preparation of creams in semisolid-state gel phase will form when ionic surfactant

and fatty alcohols coexist in the system therefore achieving self-bodied emulsion

(Strathclyde 1990) Yield stress of product which determines consumersrsquo initial

feel when applying the cream on skin should be in an appropriate range Thus the

sufficient amount of yield stress presented to avoid flow against its own gravity


simplified configuration where viscosity varied as a function of shear stress from 5 Pa to 300 Pa

165

should not cause difficulties in the distribution of creams on skin These creams

presented almost twice yield stress as E45 indicating undesired rigidity behaved

The 2nd Newtonian plateau was not obviously obtained for [2 6 6] [4 6 6] and [6

6 6] While it is worth to mention that the dynamic viscosity at 300 Pa of these

creams were greater than that of E45 cream indicating high rigidity of cream

bodies at high shear As suggested in literatures that those excess fatty

amphiphiles applied in the system which did not participate in forming hydrophilic

gel phase along with ionic surfactants build up hydrophobic gel phase contributing

for the undesired increase of consistency and viscosity and the phase is

crystallized out upon cooling procedure (Koacutenya et al 2003) This also help explain

the crystals witnessed in cream [2 6 6] [4 6 6] and [6 6 6]

By decreasing the concentration of glycerol monostearate from 6wt to 2wt

cream [2 6 2] [4 6 2] and [6 6 2] were prepared In general their viscosities at

1st Newtonian plateau were one magnitude smaller than those containing 6wt

glycerol monostearate exhibiting less stiffness texture Also the viscosity profile

presented a more pronounced Ostwald curve for every cream although details of

each stage differed between creams It can be found that increasing the

concentration of SLES from 2 wt to 6 wt in the cream system [x 6 2] leads to

cream of lower 1st plateau viscosity and yield stress which is obviously presented

in Figure 56 The limited apparent viscosity at 1st Newtonian plateau was

calculated by averaging the dynamic viscosities during the low shear plateau range

displaying in the figure for each cream where the value of cream containing 2 wt

SLES was nearly double that of cream containing 4 wt SLES and four times

larger than that of cream with 6wt SLES And 4 wt SLES in the system led to

a cream with limited viscosity twice larger than 6 wt SLES did

In terms of yield stress different literatures presented with different definitions

such as the value of onset flow (end of 1st Newtonian plateau) where the maximum

of viscosity is achieved (Mangal and Sharma 2017) and the average value

between that and onset of plunged shear thinning (Zhu et al 2005) Here the yield

stress was analysed base on the onset of flow and the onset of plunge Table 52

summarises the key flow parameters related for each cream which provided data

for the flow curve interpretation

166

Table 52 Key parameters derived from viscosity profiles of creams containing 6 wt CA and 2 wt GM with varied concentrations of SLES

Product [SLES CA GM] (wt)

[2 6 2] [4 6 2] [6 6 2]


1583plusmn002 1259plusmn000 5plusmn001


264times105 139times105 600times104





264E+05

139E+05

600E+04

0

10

20

30

40

50

10E+01

50E+04

10E+05

15E+05

20E+05

25E+05

30E+05

262 462 662

yie

ld s

tress

Pa

Vis

co

sit

y P

as

Composition of emulsifying system weight concentration of [SLESCAGM]

limited apparent viscosity

yield stress

Figure 56 Respective comparison of average of limit viscosity and corresponding yield stress among mimic creams formulated with varied emulsifying system

167

The rheological properties of semisolid creams have a close relationship with their

microstructures thus the effect of change of SLES concentration on the rheological

behaviour for creams may due to the microstructure altered It has been studied

that ionic surfactant involved in the system greatly promote the formation of

interlamellarly fixed water at the expense of bulk water than non-ionic ones plus

that more water fixed as bulk water will lead to a product with higher yield stress

(Roslashnholt et al 2012) As the interlamellarly fixed water and bulk water are in

dynamic equilibrium state in the microstructure system more ionic surfactant in the

system product with lower yield stress will be formulated (Koacutenya et al 2003) In

addition from previous study where the 2 ww and 3 ww of Eucarol AGEEC

were formulated in creams separately the amount of interlamellarly fixed water

increased when 3 ww of this ionic surfactant formulated This also indicates that

cream formulated higher quantity of ionic surfactant tends to possess lower yield

stress Also in the study of Grewe et al it has been found that increasing anionic

surfactant sodium dodecyl sulfate (SDS) mass fraction in SDScetyl alcohol (CA)

mixture caused the decrease in viscosity (Grewe et al 2015) However in the

emulsifying system containing 6 wt CA and 6 wt GM the change of SLES

concentration from 2 wt to 6 wt has little effect on creams in terms of their flow

behaviour This may be attributed to that the change of SLES concentration was

not sufficient to alter the microstructure of creams containing higher amount of fatty

amphiphiles

Within measured stress range creams containing 2 wt cetyl alcohol in the system

showed no 1st Newtonian plateau and yield stress only displaying shear thinning

behaviour with considerably low viscosity range which implied that no or weaker

structural matrix formed in these creams This indicates that cetyl alcohol is an

essential excipient as fatty amphiphile in this system Besides compared to

creams with 2 wt cetyl alcohol and 2 wt glycerol monostearate 6 wt glycerol

monostearate involved in the formulation helped increase the limiting viscosity It

can be seen from cream [2 2 6] and [4 2 6] that the dynamic viscosity reached

the magnitude of ten to the fourth during low shear range

Shear thinning behaviour is an important attribute of creams which is normally

linked with the spreadability and distribution of products on skin (Kwak et al 2015)

Steady state shear test simulates the condition when the cream is being spread on

skin in rotational motion where all 12 creams showed shear thinning behaviour

regardless whether yield stress presented or not The rate of shear thinning is also

interpreted as the shear sensitivity of products which reveals how fast the cream

168

will be sheared to a thin layer (Calero et al 2013) Regarding to six creams

containing 6 wt cetyl alcohol that presented acceptable viscosity profiles similar

rate of shear thinning was witnessed during which the viscosity sharply dropped

Thus there is no big difference of shear sensitivity between these creams also

they all presented rapid shear thinning when the external shear exceeds the critical

value

5222 Oscillatory Sweep

Viscoelastic materials exhibit both viscous and elastic behaviour making time

dependent mechanical response thus the consistency properties of creams were

analysed using small strain rheological tests in which the structure of cream system

is guaranteed not to be destroyed Based on the results of preliminary steady state

shear test creams formulated with 6 wt CA and 2 wt GM that showed

appropriate and desired rheological attributes were further studied to figure out

their elasticity and viscosity using oscillatory sweep measurements where the

viscoelasticity of a material is modelled by the combination of in-phase storage

modulus Grsquo and loss modulus Grsquorsquo Because the valid characterisation has to be

carried out in the linear viscoelastic (LVE) region oscillatory strain sweep was

preliminary applied for its determination Then a value with in this range was

selected for the following oscillatory frequency sweep

In the oscillatory strain sweep certain amount of cream samples was confined

within a 40 mm cone-plate geometry at a measuring gap of 57 mm and sinusoidally

tested with strain cyclically varied from 001 to 1000 at a constant frequency of

1 Hz 20 minutes of equilibrium time was set for cream to fully relax before the

measurement Every cream was proper loaded and measured at least duplicate

with the identical operation at 25 Referring to the results of strain sweep for

cream [x 6 2] presented in Figure 57 moduli of creams showed similar

behaviours as a function of strain Linear viscoelastic behaviour was found

during small strain amplitudes where elastic modulus Grsquo and loss modulus Grsquorsquo

remained fairly constant as strain increased and elastic response was

predominantly displayed due to GrsquogtGrsquorsquo Continuously increasing the strain both of

Grsquo and Grsquorsquo exhibited a drop after yielding A crossover point of moduli was

witnessed in every rheogram indicating the point when Grsquo=Grsquorsquo after which Grsquorsquo was

over Grsquo revealing a viscous dominated system

169

5106

1273254

07371

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()

[SLESCAGM] of [262]

G

G

Critical strain

8992

591542

07301

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()

[SLESCAGM] of [462]G

G

8292

998696

09001

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()

[SLESCAGM] of [662]

G

G

Critical strain

LVER

LVER

LVER

τy=24125

Critical strain

τy=33926

Figure 57 Oscillatory strain sweep on mimic creams formulated with 6 wt CA and 2 wt GM with varied concentration of SLES where G and G varied as function

of strain ranging from 001 to 100

170

The limit of linear viscoelastic region is needed to be defined as below that value

the storage modulus Grsquo and loss modulus Grsquorsquo are independent of applied strain

amplitude at a fixed frequency and fully describe elastic response and viscous

response resulted stress as a fundamental sinusoidal wave When being

obviously witnessed to departure the plateau Grsquo and Grsquorsquo cannot represent entirely

elastic or viscous contributions because they start altering with the strain and the

resulting sinusoidal is in distorted form Thus the conventionally defined Grsquo and Grsquorsquo

as fundamental coefficients are not applicable in the nonlinear regime Compared

to the loss modulus Grsquo the storage modulus Grsquo is more often recorded for the

determination of LVE range (Calero et al 2013)

The limit yield point of Grsquo is correlated to the end of LVE region In some literatures

beyond that Grsquo significantly drops beyond the plateau This yield value is calculated

from the intersection of horizontal line of the behaviour of Grsquo during low strain range

with power law representing behaviour of Grsquo during large strain range (Dinkgreve

et al 2016) Some others define the point only based on the linear plateau of Grsquo

Here in this study the yield value is determined as a critical strain 120574119862 when

storage modulus dropped 10 from the plateau Then the corresponding yield

stress 120591119910 was calculated by 120591119910 = 119866prime120574119862 (Dimock et al 2000)

During oscillatory strain sweep (OSS) test as increasing the strain the structural

network decays When the experiment time of oscillation for recovery is not enough

compared to the relaxation time of the degradation the sample may not recover

This results in the nonlinear viscoelasticity of the sample (Nguyen et al 2015)

The initial linear plateau of LVE was determined as a regime from the lowest

applied strain to the point where the maximum Grsquo occurred then strain

corresponding to 90 of the plateau value was recorded as critical strain Linear

plateau for creams with 2 wt 4 wt and 6 wt SLES were at same range from

001 to 0252 at frequency of 1 Hz during which the intact structure was

presented for each of them and creams all behaved like solids As can be seen in

the figure the critical strain yield stress and defined LVE region were presented

Thus a value of 02 strain from the LVE range was selected as the amplitude

for the following oscillatory frequency test This value is small enough to ensure

that the behaviour of viscoelastic is within linear region and the measured stress

is proportional to the applied strain

171

The crossover points were also indicated in the rheograms indicating the condition

when Grsquo equalled to Grsquorsquo at a specific strain normally interpreted as flow point or

flow stress 120591119891 The strain of crossover point was calculated by solving

simultaneous equations of exponential trend lines for Grsquo and Grsquorsquo followed by

interpolation to calculated corresponding modulus Before the flow stress Grsquo was

over Grsquorsquo indicating a solid domain system whereas viscous predominated in the

system when strain increased beyond the point In the transition region between

yield point 120591119910 and flow point 120591119891 storage moduli were higher than loss moduli of

three creams suggesting that although the structure of each cream was destroyed

and started to break down they still displayed in solid state And it is worth of

noticing that as increasing the SLES concentration from 2 wt to 6 wt the

difference between Grsquo and Grsquorsquo during LVE and transition region gradually

decreased implying that cream [2 6 2] behaved more elastic predominant

Some literatures compared the elastic yield stress obtained in oscillatory strain

sweep to the dynamic yield stress obtained from steady state indicating that

dynamic yield stress is much larger than the elastic yield value (Mahaut et al

2008) Similar result was found in this study except that the departure of two yield

stresses between creams with varied concentrations of SLES were small Besides

it is still under debate among researchers that whether the yield stress obtained

from steady state shear test is suitable for predicting the stability of product as the

microstructure destroyed during test (Dinkgreve et al 2016)

Oscillatory frequency sweep test was carried out for each cream The results in

Figure 58 presented storage modulus (Grsquo) loss modulus (Grsquorsquo) and complex

viscosity (ƞ) of cream [2 6 2] [4 6 2] and [6 6 2] separately as a function of

frequency (Hz) at the constant amplitude of 02 strain It can be observed that

Grsquo Grsquorsquo and ǀƞǀ were presented qualitatively similar trend as frequency rising from

001 Hz to 100 Hz where Grsquo and Grsquorsquo slowly or greatly increased and complex

viscosity decreased In addition storage moduli (Grsquo) of three creams were always

greater than loss moduli (Grsquorsquo) over the whole range of measured frequency

suggesting that elasticity domain the linear viscoelastic behaviour of all creams

This indicates creams are prepared as viscoelastic solids

Comparing dynamic sweep rheograms for three creams in parallel the departure

of Grsquorsquo from Grsquo is witnessed to be smaller as increased amount of anionic surfactant

SLES involved in the system which gives an assumption that if being swept at

this constant strain for longer time namely further decrease the frequency cream

172

[6 6 2] has greater possibility or first priority to show viscous behaviour superior

than elasticity when Grsquorsquo over Grsquo This is in line with the previous steady state results

in which cream [6 6 2] shows lower consistency and smaller yield stress

compared to other two creams [2 6 2] and [4 6 2] Loss modulus Grsquorsquo represents

the viscous component of the mechanical response of a material When a load is

applied for a long period of time or periodically and the material must resist

structure failure the viscous energy dissipation will impart superior mechanical

performance (Pouget et al 2012) Besides it is interesting to notice that beyond

the frequency of 10 Hz loss modulus Grsquorsquo of cream [4 6 2] and [6 6 2] gradually

levelled off while that of [2 6 2] still showed increasing Also complex viscosity

ǀƞǀ exhibits a decrease trend as the frequency increase for three creams which is

also an indicator for shear thinning behaviour

173

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ| P

as

G

G

P

a

Frequency Hz

[SLESCAGM] of [262]

G

G

|ƞ|

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ

| P

as

G

G

P

a

Frequency Hz

[SLESCAGM] of [46 2]

G

G

|ƞ|

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ| P

as

G

G

P

a

Frequency Hz

[SLESCAGM] of [662]

G

G

|ƞ|

Figure 58 Oscillatory frequency sweep on mimic creams formulated with 6 wt CA and 2 wt GM with varied concentration of SLES where G G and |η| varied as a

function of frequency ranging from 001 Hz to 100 Hz

174

Cox-Merz rule describes the situation for some specific materials when their

behaviour of steady shear viscosity η() versus shear rate is consistent with that

of complex viscosity versus angular frequency |ηlowast|(120596) However as shown in

rheogram (Figure 59) where the comparison between representative dynamic

viscosity profile obtained from steady state shear and complex viscosity profile

obtained from oscillatory frequency sweep for cream containing 2 wt SLES 6 wt

CA and 2 wt GM is presented The Cox-Merz rule is not applicable for the cream

[2 6 2] due to the presence of large departure between two flow curves

where|ηlowast|(120596) was superior to|ηlowast|(120596) during the whole measured range Similar

trend was found for cream [4 6 2] and [6 6 2] as well (data not shown)

The reason for this non-match result may attribute to the magnitudes of stress

applied in steady state measurement which is so large that the well-established

intermolecular and intramolecular bonds of material were disrupted when the

critical stress is exceeded thus the dynamic viscosity was measured at different

equilibrium structure of material which is different from the original state (Dogan et

al 2013) While in dynamic sweep test no significantly structural change in the

system because the imposed strain is small enough Thus the viscosity in general

resistance against deformation measured in nonlinear steady state is at variance

01

1

10

100

1000

10000

100000

1000000

000001 0001 01 10 1000

Dyn

am

ic v

isco

sit

y co

mp

lex v

isco

sit

y P

as

Shear rate s⁻sup1 angfrequency rad s⁻sup1

steady shear viscosity η(γ )

complex viscosity|η |(ω)

Figure 59 Comparison between steady shear viscosity and complex viscosity respectively varied as a function of shear rate and angular frequency for cream

containing 2 wt SLES 6 wt CA and 2 wt GM

175

with that in linear dynamic state Therefore it is well explained the situation when

the curve of complex viscosity as a function of angular frequency is above that of

shear viscosity as a function of shear rate

It has been acknowledged from steady state shear tests that in the system where

6 wt cetyl alcohol and 2 wt glycerol monostearate was applied the change of

the concentration of anionic surfactant SLES has effect on the rheological

behaviours of creams This is further proved from dynamic oscillatory frequency

results Figure 510 clearly reveals the differences of storage modulus Grsquo and loss

modulus Grsquorsquo responding to the varied frequency between creams formulated with

different concentrations of SLES ranging from 2wt to 6wt Different from steady

state shear test where the difference of apparent viscosity among creams is

significant the storage modulus Grsquo representing the elastic contribution of creams

behaved similar within small variation

However it could be noticed that the rate at which storage modulus increase with

frequency varied between creams Compared to the trend of storage modulus Grsquo

(blue triangle) of cream [6 6 2] rising over the range of frequency that (blue

square) of cream [2 6 2] is slower namely the dependence of Grsquo on frequency

500

5000

50000

001 01 1 10 100

G

G

P

a

Frequency Hz

G-cream [2 6 2] G-cream [2 6 2]

G-cream [4 6 2] G-cream [4 6 2]

G-cream [6 6 2] G-cream [6 6 2]

Figure 510 Comparison of storage and loss moduli among creams containing 6 wt CA and 2 wt GM with varied concentration of SLES where storage and loss moduli

varied as a function of frequency ranging from 001 Hz to 1000 Hz

176

for cream [6 6 2] is greater than that for cream [2 6 2] As there is no

macromolecular polymer such as thickening agent in the formulation of creams in

the formulation the characterisation of viscoelastic properties ascribed to the

crystalline gel network formed by the ionic surfactant and fatty amphiphiles

(Salehiyan et al 2018) Small strains in the linear dynamic sweep has little chance

to cause this network fully destroyed thus a weaker microstructure originally

formed in the cream is more likely reflected as more rapid growth of Grsquo over

frequency (Roslashnholt et al 2014) Loss modulus Grsquorsquo varying with frequency also

provided the same evidence As Grsquorsquo measured the dissipated energy which is

transformed from the friction heat producing when a material flows Grsquorsquo behaviour

of cream formulated with 6 wt SLES was displayed higher than that of the other

two creams indicating larger energy dissipation happened in the system Because

almost equal energy was stored referring to little difference of Grsquo between creams

the microstructure of cream with 6 wt SLES collapsed the most thereby

exhibiting a less structured system

Loss tangent (tan δ) which is the tangent of phase angle also known as dissipation

factor is defined as the proportion of loss modulus Grsquorsquo to storage modulus Grsquo (tan

δ=GrsquorsquoGrsquo) Lower value of tan δ indicates an elastic dominant viscoelastic material

and higher tan δ represents a material of viscous domain (Ha et al 2015) The

comparison of loss tangents dependant on frequency for three creams containing

different SLES concentrations is portrayed in Figure 511 where all creams

presented a decrease trend of tan δ valued below 1 as frequency rising (shorter

time duration) thereby revealing predominantly elastic nature With the increase

of SLES concentration in the formulation tan δ dependence of frequency is

approaching value of 1 indicating a more viscous response This supplementary

demonstrates that larger amount of ionic surfactant SLES involved in cream

system containing 6wt cetyl aocohol and 2 wt glycerol monostearate leads to

a more viscous domain system

177

5223 Creep and Recovery

Creep-recovery test was carried out in order to further analyse the viscoelastic

behaviour of creams and support the results of oscillatory sweep measurement

Creams formulated with 2 wt 4 wt and 6 wt SLES together with 6 wt CA

and 2 wt GM was characterised using creep test respectively where each cream

sample was subject to constant stress of 10 Pa within linear viscoelastic region for

30 minutes followed by a recovery step for another 30 minutes when the applied

stress was removed The resulted compliance for every cream was plotted as a

function of time illustrated in Figure 512 It can be seen that creep compliance

and recovery raised when the concentration of SLES in the cream increasing from

2 wt to 6 wt However all creams exhibited similar response courses under the

stress within the time range where instantaneous deformation primary creep and

secondary creep were observed during the creep process followed by

instantaneous elastic and secondary elastic recovery indicating their viscoelastic

properties

The creep compliance ratio of resulted strain to the applied stress reveals the

softness of the material That is cream of stronger structure will behave higher

compliance during creep and a weaker structured cream is related to a lower J(t)

value (Sanz et al 2017) Referring to the creep-recovery rheogram of creams

02

04

06

08

001 01 1 10 100

Dis

sip

ati

on

facto

r (

tan

δ)

Frequency Hz

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]

Figure 511 Comparison of dissipation factor among creams containing 6 wt CA and 2 wt GM with varied concentration of SLES where dissipation factor varied as a


178

cream formulated with 2 wt SLES obviously showed the lowest J(t) compared to

cream containing 4 wt and 6 wt SLES suggesting a robust structural network

formation and reinforcement induced by less amount of ionic surfactant in the

system containing 6 wt CA and 2 wt GM

The typical creep-recovery curve of semisolid material is illustrated in Figure 513

which is identified as instantaneous elastic deformation (OA) primary creep (AB)

and secondary creep (BC) followed by a fully elastic recovery (CD) of AB partially

recovery (DE) from BC and irreversible residual And the creep-recovery curve is

usually interpreted with a mechanical model frequently as the generalized Kelvin-

Voigt model which is a Maxwell unit in series with several Voigt units which is

illustrated in Figure 514

Relating the resultant creep curve to the mechanical model the instantaneous

elastic deformation of OA is associated with the Maxwell spring which is uncoupled

in Voigt unit representing the elasticity and rigidity of the gel network In molecular

aspect this reveals the primary bonds such as ionic bonds which are stronger

and stretching elastically The AB curve bending downwards indicates the

0

1

2

3

4

5

6

7

8

0 500 1000 1500 2000 2500 3000 3500 4000

J 1

0⁻sup3

Pa⁻

sup1

Time s

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]

Stress Applied Stress Removed

Figure 512 Comparison of the compliance (J) response among creams containing 6 wt CA and 2 wt GM with varied concentration of SLES where compliance varied as a function of time Curve illustrated with mean values and standard deviations were

00002 1Pa for 2 wt SLES involved 00002 1Pa for 4 wt SLES involved 00003 1Pa for 6 wt SLES involved

179

viscoelasticity of the material and could be interpreted by the series of Voigt units

where the weaker secondary bonds in part of gel network are breaking and

rebuilding when subjecting to stress and then removed This delayed elastic

response arises due to the operation internal viscous forces represented by the

dashpots coupled in Voigt units The residual dashpot in series with Voigt units

gives rise to the Newtonian flow in BC region indicating the viscous deformation

of the dispersion in liquid medium (Dolz et al 2008) During recovery phase within

time interval 30minletle60 min when the stress is removed three regions are

observed including instantaneous recovery in CD segment which is

corresponding to the uncoupled spring followed by the retardant recovery in DE

segment which is the partially recovered from AB due to the Kelvin-Voigt units

The residual compliance is a permanent deformation which is unrecoverable due

to the uncoupled dashpot

Com

pli

ance

Time

O

A

B

C

D

Instantaneous deformation

Primary creep

Secondary creep

Residual compliance

Retardant recovery

Instantaneous recovery

E

G0 G1 Gi η0

τ0 η1

1

ηi

Figure 513 Typical plot of compliance varied as a function of time in a creep-recovery test for a viscoelastic material

Figure 514 Mechanical model for interpretation of creep-recovery result

180


Formulation_Ⅰ

Droplet size distribution (DSD) analysis was carried out on three creams

respectively with [SLES CA GM] of [2 6 2] [4 6 2] and [6 6 2] at various mixing

speed of 500 rpm 700 rpm and 900 rpm separately Also the DSD of creams are

studied at different mixing time (3 min 5 min 10 min 15 min and 20 min) All the

figures presented the distribution in log-normal mode which will give a better idea

of the distribution Figure 515 shows the droplet size distribution of three mimic

creams after being mixed 10min at 500rpm As can be seen one mode is detected

in each cream Besides when the concentration of SLES increased from 2 wt to

6 wt the population of large droplets decreased and the maximum point of their

size distribution curve was shifted to smaller values

Larger size droplets indicates stronger attractive interactions exists between

flocculated oil droplets (Udomrati et al 2013) This indicates that in the formulation

where less SLES involved the attractive interactions between oil droplets are

weaker In another words stronger repulsive forces were presented in the system

containing lower concentration of ionic surfactant For the microstructure of OW

semisolid cream oil droplets are stabilised by monomolecular film and multilayers

of lamellar liquid crystals instead one monomolecular of surfactant and this multi-

Figure 515 Comparison of droplet size distribution among creams containing 6 wt CA 2 wt GM with varied concentrations SLES where volume density varied as a

function of diameter Mean values are presented in curve for each cream

181

layered interfacial film which brings repulsive electrostatic forces steric forces and

hydrational forces contributes to the increase of consistency and stability of the

system (Eccleston 1997) Combined with rheological results obtained above

where cream formulated with 2 wt presented higher consistency and higher

yields stress compared to that with 6 wt giving the evidence that the interfacial

film between droplets are stronger enough to protect them from coalescence Also

according to micelle nucleation theory with the increase of SLES more micelles

are formed in the emulsion thus the droplet size will be smaller

Creams were also examined under a polarized light microscope one day after

preparation under a magnification of times64 where The Axioplan 2 imaging


tiny amount of creams on to microscope slides with glass cover slips on top Figure

516 presents the photomicrographs of cream system containing 2 4 6 wt SLES

combining with 6 wt CA and 2 wt GM respectively The emulsifying system with

6 wt SLES contained much smaller droplets than the other two systems And the

difference of droplet size between creams formulated with 4 wt and 6 wt SLES

is not significant This relatively agreed with the rheology result

(a) (b)

(c)

Figure 516 Microscopic observation of mimic creams containing 6 wt CA 2 wt GM with varied concentrations of SLES

182

524 Thermodynamic Properties of Mimic Creams in

Formulation_Ⅰ

The thermodynamic properties of creams were analysed using differential

scanning calorimetry (DSC) experiments with the help of a Q2000 DSC system

(TA Instrument) Samples of creams were weighed into the alumina pan Then the

pans were hermetically sealed as well as the reference (air) The measurement

was performed by heating the sample from 25 degC to 90 degC at a rate of 3 degC min-1

equilibrating at 90 degC f or 3 min followed by a backward cooling procedure to -

20 degC at the same scan speed After the equilibrium at -20 degC for another 3 min

the cream was heated up back to 25 degC Therefore thermos-diagrams of creams

were obtained Similar method was applied to study thermal properties of pure

ingredients such as mixed paraffin oils SLES CA and GM The information of

melting points and crystallisation points of them was expected to be acquired also

the differences between creams formulated with different emulsifying systems

Figure 517 displayed the differential scanning calorimetry thermograms of

ramping circle between room temperature and 80 degC for CA and GM and that for

paraffin oils and SLES are respectively displayed in Figure 518 and Figure 519

-4

-2

0

2

4

20 25 30 35 40 45 50 55 60 65 70 75 80

Hea

t Fl

ow

(N

orm

aliz

ed

) Q(W

g)

Temperature T (degC)

cetyl alcohol

glycerol monostearate

Figure 517 DSC thermogram of cetyl alcohol and glycerol monostearate

183

There is no ndotherm peak showed in this range for light liquid paraffin Cetyl

alcohol showed an endotherm peaking at 50 degC with a shoulder from 45 to 55 degC

representing for the melting of the crystals The melting of glycerol monostearate

crystals witnessed at higher temperature at around 65 degC The thermogram of

SLES indicated that water existed in the sample as ice-melting peak was

witnessed at around zero degree Also crystallisation was observed at 1degC

-03

-02

-01

0

01

02

03

20 25 30 35 40 45 50 55 60 65 70 75 80

Hea

t Fl

ow

(N

orm

aliz

ed) Q

(W

g)


white soft paraffin

liquid liqiud paraffin

Figure 518 DSC thermogram of light liquid paraffin and white soft paraffin

Figure 519 DSC thermogram of sodium lauryl ether sulfate (screen short directly from software)

184

DSC scan of creams formulated with different concentrations of SLES in system

are compared in Figure 520 In this emulsifying system where SLES as ionic

surfactant and cetyl alcohol combined with glycerol stearate being used as fatty

amphiphiles with the increase of SLES concentration from 2 to 6 wt the

temperature of endotherm peak decrease from around 58 to 52 degC It has been

studied that as the formation of liquid crystals above transition temperature and

gel phase below this temperature is rapid the gel structure will be formed soon

after preparation (Ribeiro et al 2004 Zhang et al 2017a) As only one endotherm

peak was presented in each cream thermogram it cannot be concluded that there

has a trend by which high-temperature gel endotherm diminishes and low-

temperature crystalline endotherm develops However combined with the results

of rheological test with high concentration of surfactant used in the system the

limiting value of viscosity and yield stress decreased this could be explained as

the conversion of gel networks to an isotropic phase and cream system becomes

more mobile

53 Complementary Rheology Study of Creams

Formulated in Formulation_Ⅱ

From the visually observation from the appearances of formulated mimic creams

formulated in Formulation_Ⅰ it has been found that cetyl alcohol as a fatty

amphiphile played an essential role in the formulation of well-structured cream

-025

-020

-015

30 40 50 60 70

Heat

Flo

w Q

(Wg

)


262

462

662

Figure 520 Comparison of thermal behaviour among creams containing 6 wt CA 2 wt GM with varied concentrations SLES where heat flow varied as a function of

temperature ranging from 25 degC to 90 degC

185

product Further analysis was made by characterising mimic creams formulated

with varied concentration of cetyl alcohols in Formulation_Ⅱ

The effect of changing concentration of fatty alcohols on the rheological behaviour

of cream system was studied using steady state rotational measurement Two

emulsifying systems were studied where 2wt SLES and 4wt SLES were

involved separately Concentration of cetyl alcohol was increased from 5wt to

7wt with the amount of glycerol monostearate at constant of 2wt Key data

was presented in Table 53

Table 53 Key parameters derived from viscosity profiles of cream containing 2 wt SLES and 2 wt GM with varied concentrations of CA


[2 5 2] [2 6 2] [2 7 2]









In the cream system containing 2 wt of SLES the average dynamic viscosities

at 1st Newtonian plateau of during low stress range were in the same magnitude

Shear thinning behaviour was witnessed in every cream but initiating at different

critical stress which could be refer to the shear stresses at the end of 1st Newtonian

plateau Thus although there is no big difference of initial consistency between

creams formulated with different concentrations of CA their resistances to

structural deformation was varied This is more obviously found according to the

shear stress at the onset of significant drop where the stress value of cream

containing 7 wt CA (1256plusmn009 Pa) was more than twice that of cream

containing 5 wt CA (50plusmn0015 Pa) Thus larger amount of cetyl alcohol involved

tends to form a stronger structural configuration which required larger external

force to destroy (Okamoto et al 2016)

186



[4 5 2] [4 6 2] [4 7 2]









As seen from Table 54 in the system where 4 wt of SLES was applied slightly

unexpected results were presented where no significant difference of steady state

rheological behaviour between cream systems containing 5 wt and 6 wt cetyl

alcohol However a notable enhancement of consistency and yield stress was

presented when its concentration increased to 7 wt The rheological result may

be attributed the microstructural nature of creams Part of fatty amphiphiles will

form hydrophilic gel phase cooperating with ionic surfactants while the excessive

amount of that establish hydrophobic phase which contributes most to the higher

consistency of cream product (Okamoto et al 2016) Thus in the system where

more SLES involved the available sites for combination of cetyl alcohol to form

hydrophilic gel phase were increased thus although the same increment of cetyl

alcohol from 2 wt to 6 wt was presented in two cream system containing 2 wt

and 4 wt SLES respectively the presence of SLES may affect the amount of

hydrophobic phase thereby contributing to different rheological behaviour in

different systems

187


Mimic creams were prepared with surfactant systems of varied compositions

followed by characterisation with the help of rheology droplet size distribution

analysis and DSC aiming to provide a guidance for the following study of bio-

creams containing biosurfactants instead As a result systems of 6 wt cetyl

alcohol and 2 wt of glycerol monostearate cooperating with various

concentrations of sodium lauryl ether sulfate (SLES) ranging from 2 wt to 6 wt

namely cream [2SLES 6CA 2GM] [4SLES 6CA 2GM] and [6SLES 6CA 2GM]

exhibited desired rheological behaviours in comparison with E45 cream especially

for cream [4SLES 6CA 2GM] where a smooth and rich texture was witnessed

from the appearance The exhibited average apparent viscosity at 1st Newtonian

plateau was 139times105 Pas with a yield stress of over 50 Pa which is in the same

magnitude as that of E45 when rheological measurements were conducted using

the same geometry (40 mm cone-plate with a measuring gap of 57 m) Elastic

domain viscoelastic was witnessed for all creams where Grsquo was higher than Grsquorsquo

over the whole frequency range from 001 Hz to100 Hz Apart from that it showed

that increasing concentration of SLES in this system led to a decrease in viscosity

and yield stress where apparent viscosity before yield stress was 264times105 Pas

for cream containing 2 wt of SLES while that was only 6times104 Pas for cream with

6 wt SLES The same trend was confirmed by the result of oscillatory and creep

test In addition endotherm peak of creams decreased with the increased

concentration of SLES indicating a more thermal stable system containing SLES

of 2 wt compared to 6 wt In terms of the droplet size distribution analysis

higher concentration of SLES involved resulted in a system with smaller sized

droplets Cream [4SLES 6CA 2GM] was selected as a standard for bio-cream

formulation After determination of the formulae effect of various manufacturing

procedures on creams were then studied

188

Chapter 6 Variation of Creams Prepared with

Different Processes

Different compositions of surfactant systems were applied in cosmetic cream

formulations and the optimal formulations were determined from previous chapter

In order to further analyse effects of changing production process including mixing

speed mixing time and cooling procedure on the property of formulated product

mimic creams containing 6 wt of cetyl alcohol (CA) and 2 wt of glycerol

monostearate (GM) respectively with 2 4 6 wt of sodium lauryl ether sulphate

(SLES) in mixed paraffin oilswater system were prepared under various

manufacturing processes

61 Effect of Mixing Time on Cream Formulation During

Heating Procedure

The effect of different heating procedure on the performance of mimic cream was

studied where the creams were heated and mixed for varied mixing duration

ranging from 3 min to 20 min at constant mixing speed followed by being

characterized to determine the corresponding droplet size distributions (DSD) with

the help of Mastersizer 3000 The droplet size distributions of mimic creams [2 6

2] [4 6 2] and [6 6 2] being mixed at 500 rpm for 3 min 5 min 10 min 15 min

and 20 min are shown in Figure 61 where the volume density () was plotted as

the function of droplet size (microm)

It can be seen that all creams being mixed at different speed for various time

presented unimodal distribution with a population of droplets with a mean diameter

approximately ranging from 1 microm to 10 microm For different systems where different

concentrations of surfactants were involved there is no significant effect of

homogenizing duration on the distribution of droplet size only despite that for

cream containing 2 wt of SLES where an obvious decrease of droplet size was

witnessed after 20 min of mixing During the mixing process at high temperature

no significant droplet size change was displayed indicating that the microstructure

was well formed within very short time The reason for this may because the

concentration of the mixed surfactant system (SLES CA and GM) exceeds the

CMC value and a stable and rigid crystalline phase was formed at the beginning

of emulsification (Kumari et al 2018)

189

D [32] values of droplets in cream systems being mixed at 500 rpm for different

mixing duration were summarised in Table 61 where mean values were

calculated based on five replicated measurements with standard deviations

attached It clearly proved the similarity of droplet sizes when creams being mixed

for different times during heating procedure which is roughly agreed with the

observation from distribution curves

Table 61 Sauter mean diameter D[3 2] in cream containing 6 wt CA and 2 wt GM with varied concentrations of SLES being mixed at 500 rpm at ifferent mixing time The value is presented as mean value plusmn standard deviation

Mixing Time at 500 rpm

(min)

D32 of cream [SLES wt CA wt GM wt] (μm)

[2 6 2] [4 6 2] [6 6 2]

3 893plusmn0088 348plusmn0039 393plusmn0152





0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm

Cream [2 6 2] 3min5min10min15min20min

0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


Figure 61 Effect of varied mixing time during heating procedure on droplet size distribution of creams containing 6 wt CA and 2 wt GM with varied concentrations

of SLES at controlled mixing speed of 500 rpm

190

As shown in Figure 62 similar conclusion could be obtained from the situation

when mixing speed at 700 rpm where no apparent change of droplet size

distribution with varied mixing time ranging from 3 minutes to 20 minutes For

cream containing 2 wt of SLES the unimodal distribution displayed a slightly

movement to smaller droplet size with increase of mixing time which is consistent

with previous result at mixing speed of 500 rpm

Table 62 compares Sauter mean diameter D32 of each cream homogenized at

700 rpm and 900 rpm for various time which quantitatively presented that the

average droplet size was not largely altered during mixing duration within 20

minutes As for the results at 700 rpm similar to that at 500 rpm except for cream

containing 2 wt and 4 wt SLES where nearly less than 1microm decrease of droplet

size was witnessed from 3 min to 20 min mixing droplets in cream [4 6 2] were

measured with an average diameter of 443plusmn009 microm during 20 minutes mixing

While increasing the mixing speed to 900 rpm droplet size showed more sensitive

to the mixing time where the decrement of average droplet size of nearly 2 microm

was witnessed within 20-minute duration for every cream

0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm




191

Table 62 Sauter mean diameter D [3 2] in cream containing 6 wt CA and 2 wt GM with varied concentrations of SLES respectively being mixed at 700rpm and 900rpm at different mixing time The value is presented as mean value plusmn standard deviation

More cream systems containing different concentrations of surfactants were

prepared for analysing the effect of mixing time on microstructural property of

cream in terms of droplet size distribution They further agreeded with the previous

obtained argument that a unimodal shape of droplet size distribution was formed

at very early stage (mixing for 3 minutes) and it was not significantly affected by

the mixing time during heating process indicating that within certain stirring speed

range the mixing time is not a key parameter for cream formulation during heating

Mixing Time at 700rpm (min)


[2 6 2] [4 6 2] [6 6 2]








[2 6 2] [4 6 2] [6 6 2]






192

62 Effect of Mixing Speed on Cream Formulation During

Heating Procedure

Model creams were stirred at different speed while heating followed by droplet

size analysis to study the effect of stirring speed on the microstructure of the

system Figure 63 illustrates the distribution of droplet size in a representative

cream containing 2 wt of SLES 6 wt of CA and 2 wt of GM being mixed at

500 rpm for 3 min The peak of unimodal distribution significantly moved towards

smaller diameter direction while increasing stirring speed from 500 rpm to 900 rpm

indicating a significant decrease of average droplet size During the coalescence

of emulsions mixing is applied for both of dispersion and massheat transfer

Higher mixing speed tends to minimize the droplet size due to the resultant

turbulent flow and the enhancement of mixing effect (Boxall et al 2012)

However comparing the effect of mixing speed on cream formulation in different

systems where varied concentrations of surfactants involved the degree of

influence varied As the mixing time has little effect on the droplet size distribution

mean value of D32 at each mixing time was calculated for different system

presenting in Figure 64 as a function of mixing speed In the system where 2 wt

SLES involved D32 values largely reduced with increasing mixing speed While

for systems containing higher concentration of SLES the average droplet size was

0

3

6

9

12

01 1 10 100 1000

Vo

lum

e D

en

sit

y

Diameter μm

Cream [2 6 2]500rpm

700rpm

900rpm

Figure 63 Comparison of droplet size distribution among creams containing 6 wt CA and 2 wt GM with 2 wt SLES respectively being mixed at 500 rpm 700 rpm and 900

rpm for 3 minutes Data presented as the mean value

193

not greatly affected by the mixing speed Also at higher mixing speed of 900 rpm

varied concentration of SLES showed small impact on D32 values of creams

63 Effect of Cooling Procedure on Cream Formulation

Cooling is a key process in the preparation of creams during which ingredients of

dispersed phase will create three-dimensional gel structure to support cream body

and against minor stress caused deformation

Based on cream [4 6 2] containing 4 wt of SLES 6 wt of cetyl alcohol and 2

wt of glycerol monostearate different cooling procedures were carried out

followed by mixing for 10 minutes at speed of 500 rpm Table 63 summarises

different cooling procedures in the formulation

1

2

3

4

5

6

7

8

9

10

500rpm 700rpm 900rpm

D[3

2] μ

m

Mixing speed

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]

Figure 64 Comparison of D [3 2] values among creams containing 6 wt CA and 2 wt GM with varied concentrations of SLES respectively being mixed at 500 rpm 700 rpm and 900 rpm for 3 minutes Data is presented with the standard deviation as error bar

194

Table 63 Parameters for cooling process where mixing speed and mixing time are specified

The rheological properties of creams numbered A to E were analysed 20 minutes

after preparation followed by steady state shear and oscillatory sweep

measurements The viscosity profile of each cream prepared with different cooling

procedure was presented and compared in rheogram below (Figure 65) where

viscosity was plotted as function of shear stress in logarithmic coordinates All

creams prepared with different cooling procedure showed 1st Newtonian plateau

during low stress range followed by shear thinning behaviour when beyond yield

stress From visually comparison there is no big magnitude variation between

creams prepared different cooling process in terms of limiting values of viscosities

(1st Newtonian plateau) However significant departure of yield stress was

discovered between different creams

And important parameters related to the viscosity profile were quantitatively

summarised in Table 64 where key information was presented including average

limiting viscosity (η0) shear stress at end of 1st Newtonian plateau (τ0) shear stress

at onset of shear thinning plunge (τ1) and viscosity at shear stress of 300 Pa (η300)

Yield stress (τy) was determined by averaging τ0 and τ1 Besides the slope of shear

thinning (k) was calculated by joining the onset point of shear thinning and that of

2nd Newtonian plateau where the viscosity approaching level off

No Mixing speed (rpm) Cooling duration (min)

A 200 20

B 200 5

C 300 10

D 200 10

E 0 10

195

Table 64 Key parameters derived from viscosity profile of cream containing 4 wt SLES with 6 wt CA and 2 wt GM formulated with different cooling procedure

Cooling Procedure

A B C D E

200rpm 20min

200rpm 5min

300rpm 10min

200rpm 10min

0rpm 10min

times105 η0

(Pas) 068plusmn019 176plusmn039 231plusmn053 140plusmn011 055plusmn010

τ0 (Pa) 398plusmn0001 10plusmn0001 1585plusmn0002 794plusmn0001 316plusmn0003


τy (Pa) 829plusmn0001 2491plusmn0001 3948plusmn0002 2388plusmn0001 951plusmn0002

η300 (Pas) 038plusmn016 202plusmn015 517plusmn018 134plusmn004 051plusmn005

k -19923 -19405 -52341 -17865 -42169

01

1

10

100

1000

10000

100000

1000000

1 10 100 1000

Vis

cosi

ty

Pa

s

Shear stress Pa

200rpm20min

200rpm5min

300rpm10min

200rpm10min

0rpm10min

Figure 65 Comparison of different cooling procedures on cream containing 6 wt CA and 2 wt GM with 4 wt SLES where viscosity varied as a function of shear stress

ranging from 1 Pa to 300 Pa

196

For 10 min of cooling both of the average of viscosity in 1st plateau and the yield

stress of creams increased with the increase of mixing speed from 0 to 300 rpm

Thus in the cream system containing 4 wt of SLES 6 wt of cetyl alcohol and

2 wt of glycerol monostearate within a certain time of cooling higher mixing

speed will produce a more rigid cream Also as the yield stress is related to the

strength of three-dimensional microstructure of the creams higher value of yield

stress indicates that the cream needs larger stress to initiate flow (Mahaut et al

2008) However in terms of applicability of cream to the skin the yield stress

should be controlled at a moderate value A stronger gel structure of cream

systems refers to more contact surfaces lower packing fraction and stronger

packing between particles (Roslashnholt et al 2014) which could be achieved by

modify mixing speed during cooling procedure

Referring to oscillatory sweep test creams that formulated with different stirring

speed during 10-minute-cooling were oscillated sheared at a constant strain from

01 Hz to 100 Hz and the storage modulus was presented as a function of

frequency Within the linear viscoelastic region amplitude was small enough that

the structure of system kept intact during measurement As can be seen from

Figure 66 higher mixing speed contributed to the formulation of more rigid

structure which responded with higher storage modulus indicating a distinctly

elastic predominant system (Colafemmina et al 2020b)

When controlling the mixing speed at 200 rpm longer mixing time led to production

of relatively less viscous cream product Meanwhile compared to being cooled for

10 minutes while mixing the yield stress of cream sharply dropped by 23 from

2388 to 829 Pa if extending cooling time to 20 min This implies that a weaker

matrix structure formed and the cream is easier to flow at a small stress In the

rheogram of oscillatory measurement shown in Figure 67 a relatively more elastic

domain system was obtained attributed to shorter time of stirring while cooling at

a certain mixing speed of 200 rpm

Cooling procedure is significant for cream preparation as gel formation by

surfactant molecules is generally controlled by thermodynamics It has been

studied that cooling rate also largely affected the microstructure of gel formation

where fast cooling procedure (quenched) resulted in higher elastic and viscous

moduli for system containing cetyltrimethylammonium chloride (CTAC) and

cetearyl alcohol in water and the values were 4 times higher than the slow-cooling

procedure applied (Colafemmina et al 2020b)

197

100

1000

10000

100000

01 1 10 100

G

Pa

Frequency Hz

300rpm10min

200rpm10min

0rpm10min

100

1000

10000

100000

01 1 10 100

G

Pa

Frequency Hz

200rpm5min

200rpm10min

200rpm20min

Figure 66 Comparison of varied stirring speed during cooling procedure for 10 min on cream containing 6 wt CA and 2 wt GM with 4 wt SLES where storage modulus


Figure 67 Comparison of varied stirring duration during cooling procedure at controlled stirring speed of 200 rpm on cream containing 6 wt CA and 2 wt GM with 4 wt SLES where storage modulus varied as a function of frequency ranging

from 01 Hz to 100 Hz

198


In this chapter the effect of heating and cooling procedure on the performance of

creams are studied As a result during heating procedure varied mixing duration

from 3 min to 20 min almost had no influence on the droplet size distribution of

cream [2SLES 6CA 2GM] [4SLES 6CA 2GM] and [6SLES 6CA 2GM] at varied

mixing speed of 500 rpm 700 rpm and 900 rpm However higher mixing speed

led to average smaller droplets for all creams Effect of cooling procedure were

analysed with the help of rheometer coupled with 40 mm cone-plate geometry

For the system of [4SLES 6CA 2GM] in the process where cooling duration set

for 10 min higher mixing speed from 0 rpm to 300 rpm resulted in a more viscous

and rigid cream while when comparing the mixing time during cooling of 5 min 10

min and 20 min at a constant mixing speed of 200 rpm long-term stirring during

cooling procedure contributed to a less viscous cream with relatively lower yield

stress For the following preparation of bio-creams mixing at 500 rpm for 10

minutes was set for heating process and then creams were stirred at 200 rpm

during cooling for another 10 minutes

199

Chapter 7 Production of Bio-surfactants

Along with the mimic cream formulation biosurfactants were produced through

microorganism cultivation followed by structural analysis for their species

determination This chapter will display the results related to biosurfactants

production including sophorolipids (SLs) and mannosylerythritol Lipids (MELs)


Media broth in every shake flask was transferred into one experimental glass

reagent bottle for the further extraction and purification After standing for a few

hours broth separated into different layers (Figure 71 a) including oil phase

major SLs media solution and the sedimentation Due to the density difference in

SLs some of them precipitated with cell pellet in the bottom (Figure 71 b)

Oil

Media

SLs

Broth

SLs Cell pellet

Sedimentation

(a) (b)

Figure 71 Phase separation of media broth of sophorolipids production

200

Following the procedure of isolation and purification in section 3132 where n-

Hexane was applied three times for residual oil removal followed by product

extraction with equal volume of ethyl acetate biosurfactants were then dried out to

get rid of solvents through rotatory evaporation (Dolman et al 2017) The

appearance of fresh product right after rotary evaporator was shown in Figure 72

(a) which was similar to dark orange viscous syrup Products from every batch of

rotary evaporation were transferred into 50mL plastic bottles and left in fume

cupboard for 24 hours for drying as seen figure 72 (b) where the bio-surfactant

became solid-like and unable to flow This was applied for further analysis and

application in bio-cream formulation

50 mg L-1 SLs was produced from the fermentation determined with the help of

gravimetric method (Dolman et al 2017) HPLC was also carried out for measuring

the concentration of SLs The sample preparation and characterisation method of

that was introduced in in section 3133

The result of HPLC was not very clear but in general it can be seen that a nearly

flat baseline was obtained (Figure 73) Also too many sharp peaks are witnessed

indicating highly impurity of the product Even though the peaks are sharp enough

to be witnessed which means HPLC can be used for detecting sophorolipid there

is not a standard to be compared with so it is difficult to identify the fractions that

each peak stands for

(a) (b)

Figure 72 Appearance of extracted sophorolipids (a) right after rotary evaporation and (b) after 24h dried in fume cupboard

201

711 Structural Analysis of Sophorolipids (SLs)

Mass spectroscopy was preliminary applied to study the structure of produced

biosurfactants where samples were prepared following the method introduced in

section 3662 A representative mass spectrum of SLs was shown in Figure 74

where detected ions with specific mass-to-charge ratios (mz) were exhibited by

bars with their lengths indicating the relative abundance of ions

The main peaks were at the mz value of 70532 and 73332 As negative ion

electrospray was applied in the measurement the real molecular mass for these

two peaks should be 70632 and 73432 respectively It has been reported that

diacylated lactonic sophorolipid of C181 has the molecular mass of 687

(Khanvilkar et al 2013) In addition the molecular mass of acidic form is 18 more

than lactonic form (Dolman et al 2019) Therefore the structure with molecular

mass of 70532 tends to be diacylated acidic sophorolipid of C181

Regarding to the peak valued 73332 which is almost 28 more than that of

diacylated acidic sophorolipid of C181 possible structure suggested for this

molecular mass is diacylated acidic sophorolipid of C201

Figure 73 Result of HPLC measurement of sophorolipids

202

Besides another two peaks were also detected corresponding to the real

molecular mass of 68831 and 80231 The former represents for diacylated

lactonic Sophorolipids of C181 As for the latter it can be found that this structure

of SLs was unlikely to consist of a hydrophobic tail with 18 carbons (C18) as it was

92 higher than the molecular mass of diacylated acidic sophorolipid with C180

which has the maximum molecular mass among structures with C18 Thus for the

peak at mz of 80131 diacylated acidic sophorolipid of C252 was assumed As a

matter of fact this structure of sophorolipid with long chain is kind of reasonable

as the hydrophobic carbon source was rapeseed oil which contains almost 50

erucic acid (C22)

From the result of mass spectroscopy more acidic SLs were produced in the

fermentation than lactonic forms One possible reason may because that during

the fermentation the pH of the media was not maintained at the optimal value This

was also found in literature that when the pH value drops to 2 more acidic form

of SLs was presented in the product (Dolman et al 2017)

712 Surface Tension Analysis of Sophorolipids (SLs)

The surface activity of SLs was measured using method referring to section 365

Figure 75 illustrated the surface tension of SLs aqueous solutions at different

concentrations Surface tension rapidly decreased with the increase of the

Diacylated lactonic SLs

with C181

Diacylated acidic

SLs with C181

Diacylated acidic

SLs with C201

Diacylated acidic SLs

with C252

7333223

6873149

Figure 74 Representative mass spectrum of sophorolipids obtained from mass spectrometry

203

concentration of SLs solution and gradually levelled off after reaching approximate

3459 mN m-1 corresponding to a CMC value of 50 mg L-1

The CMC of SL solution (50 mg L-1) is lower than that of SLs produced by

cultivating Candida Bombicola on a medium containing sugarcane molasses with

soybean oil (5943 mg L-1) (Daverey and Pakshirajan 2009) and glucose with

soybean dark oil (150mg L-1) (KIM et al 2005) The difference of CMC value may

due to different structures of SLs that produced by cultivating the strain on different

substrates In another aspect the purification of SLs may also affect the result In

previous study the minimum surface tensions in crude and purified SL solutions

were nearly the same which are 39 mN m-1 and 36 mN m-1 respectively However

the crude SLs mixtures showed a much higher CMC value of 130 mg L-1 compared

to the purified SLs (CMC of 10 mg L-1) (Otto et al 1999)

30

40

50

60

70

80

0 30 60 90 120 150 180 210 240 270 300 330

surfa

ce t

en

sion

(m

Nmiddotm

-1)

Concentration of sophorolipid solutions(mgmiddotL-1)

Figure 75 Surface activity of SLs in water solution where surface tension varied as a function of the concentration of sophorolipids

204

72 Mannosylerythritol Lipids (MELs)

Shake flask fermentation and fed-batch fermentation were carried out for MELs

production separately After 10 days of strain cultivation orange beads were found

in the shake flasks of batch fermentation shown in Figure 76 (a) and products

with disparate morphology were obtained from fed-batch fermentation where

yellow gel-like aggregates were witnessed

721 Structural Analysis of MELs

Mass spectrometry (MS) was performed on MELs to determine whether the

product was MELs and analyse the structure composition Sample preparation and

measuring procedure has been introduced in 3662

Figure 77 presents the MS result of the product where many peaks are exhibited

on the positive mass spectrum of [M+H]+ ion This indicates that the crude product

contains oils and fatty acids (peaks at mz less than 500) and various structures

of biosurfactants

(a) (b)

Figure 76 Appearance of MELs products from (a) batch fermentation and (b) fed-batch fermentation

205

In order to identify peaks in details MS analysis was carried out within smaller

specific mass-to-ratio ranges including mz of 450-600 600-750 and 750-1050

among which the MS spectrum at mz from 600-750 is shown in Figure 78

Three major ion peaks of the [M+H]+ ion at mz 671 (67136) 697 (69737) and

657 (65738) are presented and the corresponding molecular weight was

approximately determined as 6704 6964 and 6564 The ion peak at mz 671 can

MW 6704

MW 6564

MW 6964

Figure 77 Results of mass spectrometry of mannosylerythritol lipids

Figure 78 Representative mass spectrum of mannosylerythritol lipids with mz ranging from 600 to 750

206

be interpreted as resulting from (ME-4H+ 280) + 2(acetyl group 43) + (decylenic

acid-OH- 153) + (decynoic acid-OH- 151) + (H+1) In comparison the ion peak

at mz of 697 presenting a molecular mass difference of 21 from the main peak

which is possible due to the difference in fatty acid chain Based on this calculation

Table 71 summarise some interpretation of peaks that obtained according to other

papers where the possible fatty acid chains were included (Beck et al 2019

Madihalli and Doble 2019)

Table 71 Prediction of MELs structure and corresponding possible fatty acid chains

As seen from the result most peaks that has been analysed represents MEL-A

However in order to get deeper insight into the oil or fatty acid moiety in different

structures LC-MS measurement can be taken into account Besides more purified

sample should be used for further analysis where further oil extraction is needed

[M+H+] Molecular mass Possible

structure of MELs

Possible fatty

acids chain

combinations

5352741 5343 MEL-D C81-80

6433460 6423 MEL-A C81-102

6573792 6564 MEL-BMEL-C C102-121C101-

122C81-142

6713578 6704 MEL-A C101-102C81-

122

6973735 6964 MEL-A C102-122

7133647 7124 MEL-BMEL-C C81-182C121-

142C121-

142C102-161

7313800 7304 MEL-A C101-140C120-

121C81-160

8956104 8946 MEL-A C183-183

9616177 9606 MEL-A C201-200

207

73 Thermodynamic Properties of Sophorolipids and

MELs

As can be seen from Figure 79 during the DSC scanning from room temperature

to 90degC and then ramping down to -20degC followed by a ramping up back to room

temperature SLs did not show any obvious endothermic or exothermic peaks

indicating a thermostability during the measured range So wider temperature

range is suggested on thermal study of SLs Different from SLs of which no

thermal transition witnessed with DSC scan MELs presented ice-melting peak

around zero degree and another crystallisation peak exhibited at around zero

degree which may due to water existence in the crude product shown in Figure

710 But results indicated excellent thermal stable of biosurfactants when

subjecting to temperature variation

-025

-02

-015

-01

-005

0

005

01

015

02

-20 -10 0 10 20 30 40 50 60 70 80 90

Hea

t F

low

W

g

Temperature degC

ramp up

equilibrium

ramp down

equilibrium

ramp up

-025

-02

-015

-01

-005

0

005

01

015

02

-20 -10 0 10 20 30 40 50 60 70 80 90

Hea

t F

low

W

g

Temperature degC

ramp upequilibriumramp downequilibrium

Figure 79 DSC thermogram of sophorolipids where heat flow varied as function of temperature ranging from -20 degC to 90 degC

Figure 710 DSC thermogram of mannosylerythritol lipids where heat flow varied as function of temperature ranging from -20 degC to 90 degC

208


In chapter 7 results of biosurfactant production were exhibited mainly forcused on

their structural analysis Sophorolipids (SLs) were prepared using shake flask

fermentation and the fermentation technology was referenced from Dolman et al

in our group (Dolman et al 2017) where 50 mg L-1 of SLs was produced in a batch

The structural analysis showed that diacylated acidic SLs of C181 diacylated

acidic SLs with C201 and diacylated lactonic SLs with C181 were found as main

peaks in mass spectrum Also SLs that produced presented the ability to reduce

water surface tension from 72 to 3402 mN m-1 with a critical micelle concentration

of around 50 mg L-1 Mannosylerythritol lipids (MELs) were prepared in shake-flask

fermentation using similar procedure as that applied for SLs More peaks were

observed as a result of the mass spectroscopy measurement of extracted MELs

where MEL-A predominated SLs and MELs were then formulated into bio-creams

without further purification in this study for providing the information of cream

formulation with biosurfactants instead of synthetic ones

209

Chapter 8 Production of bio-creams using

Continuous Configuration in

Formulation_Ⅲ

As concluded from previous study including formula selection and manufacturing

process optimization desired mimic creams with good performance compared to

standard E45 were produced with Formulation_Ⅲ using continuous configuration

In this chapter results of bio-creams formulated with bio-surfactants and vegetable

oils were presented and they were compared to those mimic creams in terms of

their performance

New nomenclatures of creams are applied in this chapter where surfactants

applied in creams are specified For example creams formulated with SLES SLs

and MELs combining with fatty alcohols (CA and GM) are named as cream [SLES

CA GM] [SLs CA GM] and [MELs CA GM] respectively In addition to that

corresponding concentrations of each surfactant component are specified along

with their names For example cream [2SLs 6CA 2GM] referring to a bio-cream

formulated with 2 wt SLs 6 wt CA and 2 wt GM Simplified CA and GM are

elided it turns to be cream [2SLs 6 2]

81 Reformulation of Mimic Creams Using Continuous

Configuration

Creams [2SLES 6 2] [4SLES 6 2] and [6SLES 6 2] were reproduced using

continuous configuration with the same manufacturing process applied in

Formulation_Ⅰ Then they were initially analysed using steady state shear tests

after being prepared in order to eliminating discrepancy caused by different

configurations

Rotational shear tests were performed to obtain the viscosity profile for each cream

ranging from shear stress of 5 Pa to 300 Pa using the same measuring procedure

as that being used in the analysis for Formulation_Ⅰ Their viscosity profiles were

illustrated and compared respectively between two batches in Figure 81 It can be

seen that viscosity profiles of mimic creams in Formulation_Ⅲ (line with solid filled

circle) greatly coincided with that in Formulation_Ⅰ (line with no filled circle)

especially for 1st Newtonian plateau yield stress and shear thinning behaviour

210

Using simplified configuration creams were crashed quenched by immersing the

beaker into a pot filled with large amount of cold water and the temperature was

cooled down to room temperature by 10 minutes However as for continuous

configuration freshly cold water was continuously conveyed to the container jacket

for cooling and the duration was still set as 10 minutes resulting in lower cooling

speed compared to the simplified configuration But this difference did not cause

big effects on cream performance this may due to the small quantity production of

the cream in lab scale and the only difference in cooling rate was too small to

affect the production (Roslashnholt et al 2014) Although mimic creams prepared in

Formulation_Ⅲ presents similar rheological behaviours as previous batch freshly

produced mimic creams using continuous configuration were applied for further

comparison with bio-creams

82 Creams Formulated with Bio-surfactants in Mixed

Paraffin OilsWater System

In replacement of SLES different concentrations of sophorolipids (SLs) and

mannosylerythritol lipids (MELs) were respectively formulated into the emulsifying

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [2 6 2]

First Batch

Third Batch

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [4 6 2]

First Batch

Third Batch

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [6 6 2]

First Batch

Third Batch


using simplified configurations and that in Formulation_Ⅲ using the continuous one

211

system containing 6 wt cetyl alcohol (CA) and 2 wt glycerol monostearate (GM)

incorporating with mixed paraffin oils and water Details of recipes of formulation

could be referred from group P2 and P3 in Table 37 (section 342)

821 Appearance of Creams

Pictures of bio-creams were shown in Figure 82 where the composition of each

emulsifying system were specified corresponding to each cream When having SLs

in the formulation creams presented rigid appearance with self-bodying structure

whereas creams formulated with MELs were less viscous Simply from observation

of cream appearances higher concentration of MELs in the system resulted in a

thinner product which is in consistent with mimic creams formulated with SLES

While the opposite effect was found in creams containing SLs instead where more

structured product was obtained with higher concentration of SLs involved

822 Rheological Properties of Creams

Rheological measurements were applied to analyse the flow and deformation

behaviour of bio creams formulated with SLs and MELs separately where

rotational shear oscillatory sweep and creep-recovery tests were conducted

Mixed Paraffin oils

Sophorolipids (wt) CA

(wt) GM

(wt)

2 4 6

6 2

Mannosylerythritol lipids (wt)

2 4 6

Figure 82 Appearance of bio-creams formulated with 6 wt CA and 2 wt GM respectively incorporated with varied concentrations of SLs and MELs in mixed paraffin

oils-water system

212


Non-linear rotational shear test was preliminary performed on creams using the

same sample preparation sample loading and measuring procedure as introduced

in section 36132 Figure 83 illustrates the viscosity profiles of creams [2SLs 6

2] [4SLs 6 2] [6SLs 6 2] containing 2 wt 4 wt and 6 wt SLs respectively

incorporating with same amount of fatty alcohols for stabilising mixed paraffin oils

in water where viscosities varied with increasing shear stress from 1 Pa to 30 Pa

Three bio-creams formulated with SLs all clearly showed decreased viscosity trend

as the shear stress increased indicating shear thinning behaviour which is a

property of good cream in terms of spreadability and distribution ability (Malkin

2013) In addition it is interesting to notice that the slope of shear thinning

behaviour of each cream varied to that obtained from mimic creams When beyond

the yield stress a viscosity drop was presented followed by a gradually slow

decrease which includes a short plateau then another sharp decrease of viscosity

was displayed The reason for this may due to the multiple structure of crud SLs

where the ring shaped lactonic form and opened acidic form co-existed in the

product forming various structure of micelles

Before reaching the yield stress the viscosity behaviour of cream as a function of

shear stress is usually introduced as the 1st Newtonian plateau presented as

viscosity levelling off during low shear stress range if accurate measurements were

conducted (Tatar et al 2017) As stated in previous chapter rheological

measurements in this work may be influenced by wall slip phenomenon However

as absolutely same procedure was maintained and reduplications were carried out

rheological data could be sufficient for the comparison between different creams

with varied surfactant systems For flow profiles of cream [4SLs 6 2] and [6SLs

6 2] the corresponding zero viscosity was calculated as an average and displayed

in the figure Cream containing 6 wt SLs presented higher zero viscosity (117times

105 PamiddotS) than that containing 4 wt SLs (435times104 PamiddotS) However for cream

[2SLs 6 2] no plateau was witnessed but it exhibited same curve trend of shear

thinning behaviour as other two creams Thus it is assumed that cream [2SLs 6

2] may reach zero viscosity when decreasing the shear stress below 1 Pa In this

study during the measuring range the limit viscosity of cream containing 2 wt

SLs was determined as the apparent viscosity at 1 Pa (633times103 PamiddotS)

213

The existence of the 1st Newtonian plateau reflects the formation of well-

established three-dimensional microstructure in the self-bodying cream thereby

resulting a product with a solid appearance at rest (Ahmadi et al 2020) This helps

explain the different appearance of three creams showed in Figure 83 where

creams containing 4 wt and 6 wt SLs clearly performed with solid state when

compared to that with 2 wt SLs

From the viscosity profile as a function of shear stress a bio-surfactant SLs were

proved to be a feasible substitution of chemically synthesized surfactant SLES As

introduced in chapter 521 when no ionic surfactant (SLES) involved in the

formulation containing 6 wt CA and 2 wt GM the product displayed

unhomogenized appearance where water was greatly separated from cream

While 2 wt SLs was able to contribute to the formulation of a homogenised cream

even though it showed less viscous Increase the concentration of SLs facilitated

the production of a more desired cream showing higher viscosity and yield stress

exhibiting an opposite effect compared to SLES that higher concentration of SLES

resulted in a more viscous system This may due to the non-ionic nature of SLs

As reported in literatures higher concentration of non-ionic surfactant contributes

to formation of more rigid system (Penkina et al 2020)

Figure 83 Comparison of flow behaviour among creams containing 6 wt CA and 2wt GM with varied concentrations of SLs in mixed paraffin oils-water system where viscosity varied as a function of shear stress ranging from 1 Pa to 300 Pa

214

Another biosurfactant MELs were applied to replace SLES for cream formulation

The same characterisation regarding to viscosity profile determination was

conducted as that of SLs the results is shown in Figure 84 These bio creams

displayed shear thinning behaviours within shear stress range from 1 Pa to 300 Pa

Nevertheless the limiting viscosities of creams at shear stress of 1 Pa were

unexpected lower than that of creams containing SLs MELs were introduced as a

better emulsifier in the literatures and compared to that SLs work better on the

aspect of reducing the surface or interfacial tension (Xu et al 2019) Thus MELs

were expected to behave better in the formulation of creams But this may due to

different micellar structure that formed when MELs were involved in the system as

reported in literatures that MELs tended to self-assemble and form vesicles which

is different from SLs or SLES Also a plateau was witnessed during shear thinning

range of every cream which was in the same situation as cream containing SLs

228E+03

175E+03

222E+02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Mixed Paraffin OilsCream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]

Figure 84 Comparison of flow behaviour among creams containing 6 wt CA and 2wt GM with varied concentrations of MELs in mixed paraffin oils-water system

where viscosity varied as a function of shear stress ranging from 1 Pa to 300 Pa

215


Oscillatory strain sweep (OSS) test was performed to determine the LVE range

Same procedure was applied in the analysis for bio-creams where the prepared

sample was subject to increased oscillatory strain strain ranging from 00001 to

1000 while keeping the frequency as constant of 1 Hz For the result of OSS

variations of Grsquo and Grsquorsquo were displayed as the function of the increased strain

displaying in logarithmic coordinates Then a strain was selected among plateau

values that presented on the Grsquo (γ) curve usually during low amplitude range Grsquo

and Grsquorsquo as a function of increased strain for bio-creams containing SLs is shown in

Figure 85 In every rheogram the yield point of Grsquo was displayed as 90 of the

plateau value and the crossover point was calculated using the method introduced

in section 5222 Based on the result of OSS for bio creams the strain of 001

was selected as the constant amplitude for the further OFS test The value is also

suited for bio-creams containing MELs Before the cross-over point where Grsquo

equalled to Grsquorsquo the elastic behaviour dominated the viscous one (GrsquogtGrsquorsquo) for all six

bio-creams indicating a certain rigidity if the product is solid with relatively high

viscosity during medium or high shear rate range (Mahaut et al 2008) While for

creams presented low-viscosity behaviour in shear thinning and the 2nd Newtonian

plateau they still showed GrsquogtGrsquorsquo in LVE range which indicated their gel-like

consistency and certain firmness when at rest despite that the gel structure was

weak (Pan et al 2018)

216

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()

Cream [SLs CA GM] of [2 6 2]wt (Mixed Paraffin Oils)

G

G

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()

Cream [SLs CA GM] of [4 6 2]wt (Mixed araffin Oils)

G

G

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()


G

G

Figure 85 Oscillatory strain sweep on bio-creams formulated with 6 wt CA and 2 wt GM with varied concentration of SLs where G and G varied as function


217

Oscillatory frequency sweep (OFS) test was then carried out where cream

samples were sheared under sinusoinal oscillatory strain at a constant value of

001 with the frequency increased from 001 to 100 Hz As Figure 86 presented

where SLs was applied in the formulation the result is displayed in form of storage

modulus Grsquo loss modulus Grsquorsquo and complex viscosity |ƞ| varying as a function

of frequency for cream containing different concentrations of SLs The complex

viscosity for all bio-creams decreased as the frequency increasing demonstrating

shear thinning behaviour of creams which complemented results obtained from

non-linear rotational shear test (Sanz et al 2017)

For SLs involved bio-creams except cream with emulsifying system [SLs CA GM]

of weight concentration of [2 6 2] where Grsquo and Grsquorsquo intersected at certain

frequencies the other two creams displayed gel-like character with elastic behavior

dominated over the measured frequency range (GrsquogtGrsquorsquo) This was also winessed

for bio-creams containing MELs As described in literatures (Mahaut et al 2008)

for stable dispersions or gels trend of Grsquo is often greater than Grsquorsquo and both of them

show almost parallel lines increasing with the frequency rise which is comparable

to that indicated by bio-creams

The network structure built in the dispersion is the reason for Grsquo and Grsquorsquo response

against frequency during LVE range which is usually in the form of physical

network and vice versa Grsquo-curve and additionally Grsquorsquo-curve could help confirm

whether a gel-like structure is formed in the cream product (Wang and Marangoni

2016) The three-dimentional gel network was established by interaction forces

which is mainly due to the intermolecular forces based on physical-chemical bonds

(secondary bonds) This type of bonds generally show lower energy than chemical

bonds (primary bonds) contributing to intramolecular forces (Koacutenya et al 2003)

OFS test could be applied to study the strength of internal structure by comparing

the Grsquo -value at a low frequency but not able to distinguish the type of network

as both of inermolecular and intramolecular forces result in relatively constrant

structural strength during LVE range of cream products (Zhao et al 2013)

218

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ

| P

as

G

G

Pa

Frequency Hz

Cream [SLs CA GM] of [2 6 2]wt

G

G

|n|

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ

| P

as

G

G

Pa

Frequency Hz


G

G

|n|

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ|

Pa

s

G

G

Pa

Frequency Hz


G

G

|n|

Figure 86 Oscillatory frequency sweep on bio-creams containing 6 wt CA and 2 wt GM with varied concentration of SLs where G G and |ƞ|varied as function of

frequency ranging from 001 Hz to 100 Hz

219

Althoug both of bio-creams formulated with SLs and MELs showed that Grsquo was

greater than Grsquorsquo within the frequency range the degree of curves (Grsquo and Grsquorsquo)

between them was different For MELs incorporated bio-creams Grsquo - and Grsquorsquo- curve

nearly presented as parallel straight lines and probably no likelihood of crossing

over with each other at any point However relatively obvious curvature was found

for Grsquo and Grsquorsquo responsed by cream containing SLs resulting the convex Grsquo curve

and and concave Grsquorsquo curve and the curvature increased when lower concentration

of SLs was in the system As a result the tendency of Grsquo- and Grsquorsquo-curve meeting

at certain frequencies was witneesed in the rheogram of cream containing 2 wt

SLs and two regions near crossover points were illustrated in Figure 87

During low frequency range from 001 Hz (ωasymp00628 rad s-1) to 01 Hz (ωasymp0628

rad s-1) the cream sample was exposed to very slow motion and responsed long-

term behavior which helped characterise its internal structural strengthe when at

rest (Pan et al 2018) As can be seen from Figure 87 (left rheogram) the average

curve of Grsquo was dominant that of Grsquorsquo but the overlaps of error bars indicated that

Grsquo and Grsquorsquo probably crossed over with each other before reaching the frequency of

006 Hz (ωasymp04 rads) Thus during with low frequency range that is long-term

oscillation frequency sweep teset indicated that cream [2SLs 6 2] behaved

between liquid and gel-like suggesting the long-term storage unstability Another

crossover point was found during high frequency range from 10 to 100 Hz (right

rheogram in Figure 87) approximately around 8 Hz after which Grsquorsquo was greater

10E+02

10E+03

001 01

G

G

Pa

Frequency Hz

[SLs CA GM] of [2 6 2] wt

G

G

10E+03

10E+04

10 100

G

G

Pa

Frequency Hz


G

G

Figure 87 Specific oscillatory frequency range of oscillatory frequency sweep test for SLs-involved cream including the range between 001 and 01 (left) and that between

10 and 100 (right) showing crossover of G and G

220

than Grsquo indicating the cream behaved as a viscoelastic liquid at higher frequencies

This may because of sample degradation and measuring inherent problems (Pan

et al 2018)

Steady state rotational test (SSS) was previously applied to determine the ldquoyield

stressrdquo for analysing the structural network built in cream when at rest thereby

evaluating the consistency of sample This was realised in osillatory frequency

sweep (OFS) as well where Grsquo and if necessary along with Grsquorsquo were analysed at

low frequencies But they were not in the same meauring range and just

complementing each other For bio-creams involved MELs although viscosity

profiles from SSS showed no yield stress of creams within the measured shear

stress range suggesting no network structure established storage moduli

response against frequency presented that Grsquo was predominant thus indicating

gel-like structure and certain stability of creams

As seen from Figure 88 and 89 Cream containing 6wt of SLs presented higher

Grsquo compared to that containing 4 wt and 2 wt of SLs showing a higher stability

and rigid gel network However higher concentration of MELs involved in the

formulation led to a weaker gel structured cream showing lower Grsquo-values against

frequencies compared to creams with lower concentration of MELs The reason for

this may because the difference of micelles or liquid crystals structure formed by

MELs and SLs molecules leading to different effects on rheological behaviour of

creams (Kelleppan et al 2018 Worakitkanchanakul et al 2009)

221

10E+02

10E+03

10E+04

10E+05

001 01 1 10

G

G

P

a

Frequency Hz

Mixed Paraffin Oils

G-cream [6SLs 6 2] G-cream [6SLs 6 2]



10E+02

10E+03

10E+04

001 01 1 10

G

G

P

a

Frequency Hz

Mixed Paraffin Oils

G-cream [2MELs 6 2] G-cream [2MELs 6 2]G-cream [4MELs 6 2] G-cream [4MELs 6 2]G-cream [6MELs 6 2] G-cream [6MELs 6 2]

Figure 88 Comparison of G and G as function of frequency ranging from 001 Hz to 10 Hz among bio-creams containing 6 wt CA and 2 wt GM with varied concentrations

of SLs in mixed paraffins-water system

Figure 89 Comparison of G and G as function of frequency ranging from 001 Hz to 10 Hz among bio-creams containing 6 wt CA and 2 wt GM with varied

concentrations of MELs in mixed paraffins-water system

222


Results of creep and recovery test that carried out on bio-creams containing SLs

and MELs are shown in Figure 810 and 811 respectively As introduced in the

creep results for creams having SLES in the system a primary creep and

secondary creep are expected to be found in the creep compliance response under

the stress as function of time especially primary creep that represented by spring

element indicating a system showing elastic behaviour (Dogan et al 2013) While

for bio-cream formulated with 2 wt SLs only secondary creep region dominates

indicating a viscous liquid behaviour However with the increase of SLs

concentration secondary creep range was presented as seen the creep curve of

bio-cream containing 4 wt and 6 wt SLs in the system Therefore higher

concentration of SLs in the system resulted in a more elastic behaved product

which is the desired property in semi-solid system

For the system where MELs was incorporated with paraffin mixed oils in water no

primary creep phenomena showed in all three bio-creams containing different

concentrations of MELs Also during recovery process after 30-minutes stress

shear within LVE range bio-creams showed no strain recovery Thus it means that

MELs is not a good substitute surfactant of SLES in this formulation of cream

product with paraffin oils in water system containing 6 wt cetyl alcohol and 2 wt

0

005

01

015

02

025

03

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa

⁻sup1

Time s

Mixed Paraffin Oils

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

0

03

06

09

12

15

18

0 1000 2000 3000 4000

J

10

⁻sup2 P

a⁻sup1

Time s

Figure 810 Comparison of compliance as a function of time among bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of SLs in mixed

paraffins-water system

223

glycerol monostearate in terms of creep response as they all behaved as viscous

liquid and no elasticity witnessed This agree with the results obtained from steady

state shear and oscillatory sweep tests

823 Thermodynamic Properties of Creams

DSC measurement was carried out to characterise bio-creams formulated with

sophorolipids (SLs) and mannosylerythritol lipids (MELs) separately results of

corresponding thermograms of SLs and MELs were respectively displayed in

Figure 812 and 813 No obvious difference was found upon heating curve for both

thermograms where for bio creams containing different concentrations of SLs a

melting point was found at around 36 degC and similar for that of MELs While upon

cooling down for creams with SLs exothermal peaks were observed and with an

increase of SLs concentration crystallization temperature moved to lower

temperature resulting in smaller supercooling temperature difference (difference

between melting point and the cooling crystallization temperature) and thus higher

solidification rate of the material (Zhang et al 2017a) However the DSC result

for creams formulated with MELs with mixed paraffin oils in water was unable to

provide pronounce information Thus additional measurement is needed where

lower heating or cooling rate is suggested

0

1

2

3

4

5

6

7

8

9

10

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa⁻sup1

Time s

Mixed Paraffin Oils

Cream [6MELs 6 2]

Cream [4MELs 6 2]

Cream [2MELs 6 2]

Figure 811 Comparison of compliance as a function of time among bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of MELs in mixed


224

-04

-03

-02

-01

0

01

02

03

04

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

Wg

Temperature degC

Mixed Paraffin Oils

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

-04

-03

-02

-01

0

01

02

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

mW

mg

Temperature degC

Mixed Paraffin Oils

Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]

Figure 812 DSC thermograms of bio-creams formulated with varied concentrations of SLs in mixed paraffins-water system

Figure 813 DSC thermograms of bio-creams formulated with varied concentrations of MELs in mixed paraffins-water system

225

83 Creams Formulated in Vegetable OilsWater System

As the demand for greener product vegetable oils coconut oil and vegetable

shortening were considered as the substitutions for mixed paraffin oils (light liquid

paraffin and white soft paraffin) with the same weight concentration Chemically

synthesized surfactants SLES biosurfactant SLs and MELs of 2 wt 4 wt and

6 wt were respectively incorporated with CA and GM as the emulsifying system

Recipes could be referred from Table 7 in section 342 (group C1-C3 and V1-V3)


Mimic creams containing different concentration of SLES were preliminary

formulated with coconut oil and vegetable shortening separately shown in Figure

814 Yellow products were formulated with vegetable shortening while white ones

were those with coconut oils No significant differences of consistency between

creams were witnessed and all of them showed a rigid solid state after preparation

Figure 814 Appearance of mimic creams formulated involving SLES respectively with coconut oil and vegetable shortening in water containing surfactant system of 6 wt cetyl alcohol and 2 wt glycerol monostearate with varied concentrations of sodium

lauryl ether sulfate

Coconut Oil

SLES (wt) CA

(wt) GM

(wt)

2 4 6

6 2

2 4 6

SLES (wt)

Vegetable Shortening

226

Pictures of bio creams with coconut oil and vegetable shortening in water are

presented in Figure 815 and 816 separately With nearly 27 wt coconut oil in

the formulation white semi-solid products were obtained presenting different

appearance with different concentrations of bio-surfactants When SLs of 2 wt

was involved less viscous emulsion were presented Higher concentration of SLs

obviously resulted in a structured cream in solid state with higher rigidity On the

contrary the lower concentration of MELs involved the higher stiffness of product

was made But the cream was unacceptable due to the undesired hardness and

coarse appearance when 2 wt of MELs was involved With higher concentration

of MELs in the system where 6 wt applied a smooth semi-solid cream with more

desired appearance was formulated

Still when vegetable shortening applied instead of coconut oil colour of the

product turned to yellow as seen in Figure 816 Products having SLs in the system

showed suitable rigidity from the appearance as semi-solid cream However

these coarse-grained creams were not smooth as required As for creams

containing MELs in the emulsifying system products seemed to be worse based

on their appearance as they presented as the aggregation of granules but not

Coconut Oil

Sophorolipids (SLs) (wt) CA

(wt) GM

(wt)

2 4 6

6 2

Mannosylerythritol lipids (MELs) (wt)

2 4 6

Figure 815 Appearance of bio-creams formulated involving SLs and MELs respectively with coconut oil in water containing surfactant system of 6 wt cetyl alcohol and 2

wt glycerol monostearate with varied concentrations of sodium lauryl ether sulfate

227

homogenized creams with acceptable consistency The analysis from the

appearances of creams was direct but not accurate so further characterisation

was conducted to determine their properties qualitatively and quantitatively


Series of rheological tests were carried out to study the flow and deformation of bio

creams formulated with vegetable oils where viscosity profile was determined by

conducting rotational shear test (steady state shearSSS) and viscoelasticity

behaviour was analysed with the help of oscillatory frequency sweep (OFS) and

creep test


As previous introduced the viscosity profile could be obtained by carrying out SSS

test where cream sample was subject to shear stress ranging from 1 Pa to 300 Pa

and corresponding viscosity change was recorded Characterisations were

conducted at 25 degC for every cream sample same sample preparation was made

prior to the test and minimum in duplicate Also 40 mm cone-plate geometry was



(wt) GM

(wt)

2 4 6

6 2


2 4 6

Figure 816 Appearance of bio-creams formulated involving SLs and MELs respectively with vegetable shortening in water

228

applied and creams were confined within a gap of 57 mm which is consistent as

previous characterisation for mimic creams

As mentioned in previous chapters rheological results that obtained in this work

were applied as indices for the comparison between creams formulated with

different compositions of surfactants and actual interpretation of flow properties

for individual cream system required more work to be done for further eliminating

wall depletion problem Figure 817 and 818 represents the viscosity change of

mimic creams respectively formulated with coconut oil and vegetable shortening

emulsified by SLES as a function of shear stress All creams presented the shear

thinning behaviour which is desired There was no big difference of zero-shear

viscosity and yield stress between creams containing different concentrations of

SLES and this was also found in viscosity profiles of creams having vegetable

shortening as oil content (Figure 818) However as for vegetable shortening

formulated in creams flow curves seemed to be largely affected by sample dryness

and wall slip phenomena where prominent sudden breaks were observed

compared to those for creams formulated with coconut oil (Hatzikiriakos 2012)

Even though more SLES involved led to the production of less viscous cream

which was in accordance with mixed paraffin oils involved system Vegetable

shortening involved creams presented approximate one magnitude larger of zero

shear viscosity and yield stress value respectively than coconut oil involved creams

did (Figure 817) This may because the difference of physical property between

two vegetable oils (Chizawa et al 2019)

The zero shear viscosity (limiting viscosity at shear stress of 5 Pa) for the system

of mixed paraffin oil incorporating with 4 wt of SLES in water was 139times105 Pas

a comparable value of 1times105 Pas was obtained for coconut oilwater4 wt SLES

system indicating the potential of coconut application in the replacement of

paraffin mixed oils in terms of their rheological behaviour As a matter of fact

similar coconut oil and mixed paraffins showed same magnitude of Grsquo and Grsquorsquo trend

with varied frequency from 01 Hz to 100 Hz (data not shown)

229

205E+05

108E+05

546E+04

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

01 1 10 100 1000

vis

cosi

ty

Pas

Shear Stress Pa

Coconut Oils

Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]

276E+06

248E+05

130E+05

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

10E+07

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa


Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]

Figure 817 Comparison of flow behaviour among mimic creams containing 6 wt CA and 2 wt GM with varied concentrations of SLES in coconut oil-water system where

viscosity varied as a function of shear stress ranging from 1 to 300 Pa

Figure 818 Comparison of flow behaviour among mimic creams containing 6 wt CA and 2 wt GM with varied concentrations of SLES in vegetable shortening-water

system where viscosity varied as a function of shear stress ranging from 1 to 300 Pa

230

As can be seen from Figure 819 for the system of coconut oil in water bio creams

containing different concentrations of SLs where 2 wt 4 wt and 6 wt applied

showed generally shear thinning behaviour during the shear stress range from 1

Pa to 300 Pa where the limit viscosity was at nearly 104 Pamiddots for all creams And

no obvious difference between viscosity profiles of them when different

concentration of SLs applied but similar as that mentioned in the case where SLs

involved in the system of mixed paraffin oils in water three stages plateau could

be witnessed especially for cream [6SLs 6 2] This obviously related to the

complex structures of SLs (Ankulkar and Chavan 2019) As a result bio creams

containing SLs as surfactant for emulsifying coconut oil in water behaved less

viscous with a relatively weak structural network

When vegetable shortening emulsified in water with the help of different

concentrations of SLs mixed with CA and GM all creams performed shear thinning

behaviour where zero shear viscosity values were over 105 Pamiddots which can be

seen from Figure 820 However predominant wall slip phenomenon seems affect

the result of system where 2 wt SLs was involved as the sudden break presented

(Barnes 1995) This was found in the situation where SLES was applied with

vegetable shortening in water But for comparison higher concentration of SLs in

181E+04167E+04

165E+04

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Coconut Oil

Cream [6SLs 6 2]

Cream [4SLs 6 2]

Cream [2SLs 6 2]

Figure 819 Comparison of flow behaviour among bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of SLs in coconut oil-water system where


231

the cream resulted in more rigid cream with higher viscosity and yield stress which

agreed with the results obtained for SLs being applied in mixed paraffin oils and

water system

Figure 821 represents effect of different concentrations of MELs on flow behaviour

of bio-creams with coconut oil MELs performed better rheological behaviour in

coconut oil-in-water system compared to SLs All creams showed desired

viscosity profiles when subjecting to shear stress from 1 Pa to 300 Pa presenting

desired shear thinning behaviours and reasonable zero shear viscosity

Interestingly although higher concentration of MELs involved made the bio-cream

become less viscous with lower yield stress the trend was reversed during high

shear range and cream with 6 wt of MELs became more viscous than 2 wt of

that But the difference of viscosity was very small at 300 Pa This phenomenon

occurred may due to the dryness of sample while being measured at high shear

stress

Vegetable shortening-in-water system containing MELs was presented in Figure

822 and very high zero viscosity was obtained during low shear range indicating

undesired rigidity of the product even though this result was not seemed in line

with their appearances But viscosity profiles of all bio creams formulated with

128E+05

271E+05

925E+05

100E-02

100E-01

100E+00

100E+01

100E+02

100E+03

100E+04

100E+05

100E+06

100E+07

01 1 10 100 1000

vis

cosi

ty

Pas

Shear Stress Pa


Cream [6SLs 6 2]

Cream [4SLs 6 2]

Cream [2SLs 6 2]

Figure 820 Comparison of flow behaviour among bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of SLs in vegetable shortening-water system

where viscosity varied as a function of shear stress ranging from 1 to 300 Pa

232

vegetable shortening behaved not as good as that with coconut oil which could be

correlated with aggregated clusters presented in those vegetable shortening-in-

water bio creams (Chizawa et al 2019) Again wall slip was obvious for the

formulation with vegetable shortening Briefly summarised from results of steady

state shear coconut oil could be a promising alternative for mixed paraffin oils in

the formulation of cosmetic cream with SLES CA and GM as the emulsifying

system and even for bio creams incorporating SLs and MELs However as the

difference of physiochemical properties between vegetable shortening and mixed

paraffin oils or coconut oils those creams formulated with vegetable shortening

failed to present desired performance although wall slip phenomenon may exist

for these systems comparison could be sufficiently made when consistent

measuring procedure was carried out using 40 mm cone-plate geometry at a

measuring gap of 57 mm

118E+05

171E+04

57E+03

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Coconut Oil

Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]

Figure 821 Comparison of flow behaviour among bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of MELs in coconut oil-water system where


233

8322 Oscillatory Frequency Sweep

Results of oscillatory frequency sweep (OFS) for creams were presented where

storage modulus Grsquo and loss modulus Grsquorsquo changing with frequency was

measured The test was conducted within linear viscoelastic range of every sample

The LVE range was determined by carrying out oscillatory strain sweep tests

(OSS) and then a value of strain was selected for the following OFS tests

Figures 823 and 824 showed rheograms of strain sweep for the mimic cream

containing 6 wt SLES and the bio cream containing 6 wt MELs respectively

with coconut oil in water which separately represented for the determination

of strain for mimic creams and bio creams

For mimic creams involving 6 wt SLES in the system storage modulus Grsquo was

independent with increased strain until reaching the yield strain 120574119910 at around

075 During this low strain range the curve of Grsquo was over Grsquorsquo indicating a solid

domain system Moduli decreased with increasing the amplitude (strain) and a

crossover point of Grsquo and Grsquorsquo was witnessed in the rheogram This point suggested

the transition of sample from gel-like structure to liquid-like structure (Awad et al

2011) Same trend of moduli dependence on strain was achieved in the system

of bio-creams But 120574119910 was smaller than that for mimic cream which was less than

639E+05

569E+05

214E+06

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

10E+07

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa


Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]

Figure 822 Comparison of flow behaviour among bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of MELs in vegetable shortening-water system


234

01 (00895 shown in the figure for the selected cream) indicating a less

viscous system The amplitude was determined at strain of 01 for mimic creams

and that of 001 for bio creams with vegetable oils in water The selected strains

were accordingly applied for other creams as they were proved to be within their

LVE range

00895

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

0001 001 01 1 10

G

G

Pa

strain()

Cream [MELs CA GM] of [6 6 2] (Coconut Oil)

G

G

0746510E-01

10E+00

10E+01

10E+02

10E+03

10E+04

0001 001 01 1 10 100

G

G

Pa

strain()

Cream [SLES CA GM] of [6 6 2] (Coconut Oil)

G

G

Figure 823 Oscillatory strain sweep on mimic creams containing 6 wt CA and 2 wt GM with 6 wt SLES in coconut oil-water system where Gand G varied as function of

strain ranging from 001 to 100

Figure 824 Oscillatory strain sweep on bio-creams containing 6 wt CA and 2 wt GM with 6 wt MELs in coconut oil-water system where G and G varied as function


235

Oscillatory frequency sweep was applied afterwards As a result the storage

modulus Grsquo and loss modulus Grsquorsquo of cream containing different concentrations

of SLES SLs and MELs with vegetable oils in water are respectively shown in

Figure 825~830 as a function of frequency ranging from 001 to 100 Hz In

general all cream samples formulated with different concentration of surfactants

incorporated with fatty alcohols in vegetable oils and water system behaved as

structured gel as Grsquo was higher than Grsquorsquo over the whole measured frequency range

at strain within linear region for every sample The mechanical spectra namely the

trends of Grsquo and Grsquorsquo changing with oscillatory frequency measured in LVE range

were applied to illustrate the structural characters of samples

50E+01

50E+02

50E+03

50E+04

001 01 1 10 100

G

G

P

a

Frequency Hz

Coconut Oils

G-cream [2SLES 6 2] G-cream [2SLES 6 2]



Figure 825 Oscillatory frequency sweep on mimic creams containing 6 wt CA and 2 wt GM with varied concentrations of SLES in coconut oil-water system where G G

and |ƞ|varied as function of frequency ranging from 001 to 100 Hz

236

50E+01

50E+02

50E+03

50E+04

001 01 1 10 100

G

G

P

a

Frequency Hz





10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

G

G

P

a

Frequency Hz

Coconut Oil

G-cream [6SLs 6 2] G--cream [6SLs 6 2]

G--cream [4SLs 6 2] G--cream [4SLs 6 2]


Figure 826 Oscillatory frequency sweep on mimic creams containing 6 wt CA and 2 wt GM with varied concentrations of SLES in vegetable shortening-water system where G G and |ƞ|varied as function of frequency ranging from 001 to 100 Hz

Figure 827 Oscillatory frequency sweep on bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of SLs in coconut oil-water system where G G and

|ƞ|varied as function of frequency ranging from 001 to 100 Hz

237

50E+01

50E+02

50E+03

50E+04

001 01 1 10

G

G

P

a

Frequency Hz

Coconut Oil

G-cream [2MELs 6 2] G-cream [2MELs 6 2]



10E+02

10E+03

10E+04

10E+05

10E+06

001 01 1 10 100

G

G

P

a

Frequency Hz





Figure 828 Oscillatory frequency sweep on bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of SLs in vegetable shortening-water system where G

G and |ƞ|varied as function of frequency ranging from 001 to 100 Hz

Figure 829 Oscillatory frequency sweep on bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of MELs in coconut oil-water system where G G and


238

When different concentrations of SLES were involved in the formulation where

coconut oil was applied curves of Grsquo for every cream did not display huge

departure from each other indicating a similarity in terms of gel strength As

previous obtained from steady state shear test zero shear viscosity and yielding

properties were not significantly affected by the concentrations of SLES (increasing

from 2 wt to 6 wt) when coconut oil was emulsified with water which coincided

with the oscillation test Even though during lower oscillatory frequencies less

SLES involved cream (2 wt) displayed more obvious solid-structural properties

compared to higher ones did indicating longer stability of system containing lower

concentration of SLES (Kelleppan et al 2018) This is more obvious in the system

of vegetable shortening-in-water as larger difference of Grsquo between creams with

varied concentrations of SLES is witnessed especially at low frequencies

although as previous steady state shear results pointed out that the flow behaviour

of vegetable shortening incorporated creams exhibited undesired performance

The trends of Grsquo and Grsquorsquo of creams containing 2 wt 4 wt and 6 wt of MELs

was similar to that involved SLES instead where increased MELs led to products

showing more viscous structural properties Moreover concentration of MELs had

a significant influence on the viscoelastic properties of creams as seen from Figure

50E+01

50E+02

50E+03

50E+04

50E+05

50E+06

001 01 1 10

G

G

P

a

Frequency Hz





Figure 830 Oscillatory frequency sweep on bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of MELs in vegetable shortening-water system where

G G and |ƞ|varied as function of frequency ranging from 001 to 100 Hz

239

829 that Grsquo of cream [2MEL 6 2] are shifted one magnitude lower when 6 wt

MELs was applied But in the system where SLs participating the effect of

surfactant concentration on rheological properties and characters was opposite

compared to MELs or SLES From the Figure 827 and 828 it can be seen that

moduli of SLs involved cream [2SLs 6 2] [4SLs 6 2] and [6SLs 6 2] suggested

that more SLs involved in the formulation contributed to the product with more

pronounced solid dominant structure and rigid gel-like behaviour Again whether

for coconut oil or mixed paraffin mixed oils the influence of surfactant

concentration on flow property is not significant indicating the potential of altering

the formulation using vegetable oils (Salehiyan et al 2018)


When coconut oil and vegetable shortening being emulsified in water the system

with SLES showed good elastic behaviour in terms of creep test where primary

creep was witnessed and the creep response of cream containing SLES in

coconut oil-water system is similar to that in mixed paraffin oils-water system This

is found in almost all rheological tests And the reason may due to coconut oil has

similar physicochemical properties compared to the mixed paraffin oils

(Terescenco et al 2018a) The representative result of creep test of cream

involving SLES with vegetable shortening in water is shown in Figure 831 where

all creams present elastic behaviour with the presents of primary creep and

recovered strain In addition 6 wt SLES in the system greatly decrease the

rigidity of product as compliance sharply increased when compared to 2 wt and

4 wt involved

Those MELs involved systems when having coconut oil in water performed well

in terms of viscoelastic property As can be seen from Figure 832 all creams

showed good viscoelastic properties and it showed similar effect as SLES where

lower concentration of MELs or SLES in the system tends to result in a more rigid

cream with good elastic behaviour From Figure 833 as for creams containing

SLs with coconut oils in water the result was similar to that with mixed paraffin

oils in water where higher concentration of SLs had the potential to produce a

product exhibiting more obvious elasticity especially for cream containing 2 wt

of SLs merely secondary creep was witnessed indicating a viscous system

(Nguyen et al 2015)

240

Figure 831 Comparison of compliance as a function of time among mimic creams containing 6 wt CA and 2 wt GM with varied concentrations of SLES in vegetable

shortening-water system

Figure 832 Comparison of compliance as a function of time among bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of MELs in coconut oil-

water system

241


DSC measurement was carried out and expected for investigating the thermal

properties of creams and the effect of changing surfactants on the performance of

cream Creams formulated with vegetable oils (coconut oil and vegetable

shortening) respectively incorporated with SLES SLs and MELs were heated up

from room temperature to 90degC at a rate of 3degC min-1 followed by cooling down

back to room temperature at the same rate As can be seen in Figure 834 and

835 showing the DSC result of SLES and MELs separately applied in the cream

with vegetable shortening in water although higher concentration of SLES leading

to a lower melting point and decrease in crystallisation temperature change is

insignificant so further investigation is needed in terms of procedure modification

of DSC (Zhang et al 2017a) Similar no obvious trend could be witnessed from

DSC result for creams containing MELs with vegetable shortening in water

However creams with MELs exhibited broader range of melting compared to those

with SLES in the system of vegetable shortening in water indicating higher

impurity of the system which may due to the multiple structure of MELs (Okamoto

et al 2016)

0

01

02

03

04

05

06

07

08

09

1

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa

⁻sup1

Time s

Coconut Oil

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

0

2

4

6

8

0 1000 2000 3000 4000

J

10

⁻sup2 P

a⁻sup1

Time s

Figure 833 Comparison of compliance as a function of time among bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of SLs in coconut oil-

water system

242

-03

-02

-01

0

01

02

03

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

mW

mg

Temperature degC


Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]

Figure 834 DSC thermograms of mimic creams containing 6 wt CA and 2 wt GM with varied concentrations of SLES in vegetable shortening-water system

Figure 835 DSC thermograms of bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of MELs in vegetable shortening-water system

243

As shown in Figure 836 in the system where SLs was involved multiple

endothermic peaks were witnessed within temperature range between 30degC and

40degC indicating inhomogeneous system with uninvolved component (Drzeżdżon

et al 2019) but the it was different when 2 wt SLs was involved where less

melting points existed Glass transition was found for all three SLs-involved creams

and 2 wt SLs exhibiting a higher crystallisation temperature However further

DSC measurements are suggested by modifying the heating rate and temperature

range for giving more information in terms of thermal properties of creams and

correlating this to their microstructure It could also help optimizing the formulation

process such as heating and cooling temperature control (Pivsa-Art et al 2019)

Figure 836 DSC thermograms of bio-creams containing 6 wt CA and 2 wt GM with varied concentrations of SLs in coconut oil -water system

244


In chapter 8 mimic creams and bio creams were preliminary prepared with mixed

paraffin oils with water incorporating with sodium lauryl ether sulfate (SLES)

sophorolipids (SLs) and mannosylerythritol lipids (MELs) separately with 6 wt

cetyl alcohol and 2 wt glycerol monostearate Rheological measurements were

carried out using a 40 mm cone-plate geometry and a constant measuring gap was

set as 57 mm results of which were applied as indices for comparing the effect of

different surfactants on cream performances For the system having SLs in the

formulation creams were prepared with desired limiting viscosity which is in the

same magnitude as that of mimic creams From results of oscillatory frequency

sweep tests solid dominant viscoelasticity was witnessed for creams containing

SLs within the test frequency range from 001 to 100 Hz presenting as Grsquo was over

Grsquorsquo even though there has a high possibility of the cross point of Grsquo and Grsquorsquo which

indicates a glass transition It is interesting to observed that higher concentration

of SLs resulted in a more flexible cream system with relatively lower limit viscosity

and yield stress which is in the opposite trend as that for SLES involved system

This may due to the reason that SLs are non-ionic molecules and sufficient higher

concentration in the system tend to form a well-structured system (Ren 2017)

This was also witnessed from creep test where compared to the system containing

2 wt of SLs significant primary creep was witnessed for the system containing 4

wt SLs indicating an elastic behaviour

Creams were then prepared using vegetable oils such as coconut oil and vegetable

shortening as an alternative to mixed paraffin oils consisting of light liquid oil and

white soft paraffin in order to provide the information of using vegetable oils for

formulating ldquogreenerrdquo cosmetic creams As a result creams formulated with

coconut oil presented desired results where creams were prepared with

reasonable consistency and self-bodying structure both for mimic creams

containing SLES and bio creams formulated with biosurfactants However

vegetable shortening was not a desired substitute for cream preparation due to

the unfavourable colour granular texture and unexpected high yield stress in

comparison with other creams characterized in this work

245

Chapter 9 Conclusion and Future Work

Human-friendly emulsions play a significant role in various industries especially

for personal care products that closely related to peoplersquos everyday life As a key

component in their formulation surfactant system is usually inevitable for

enhancing emulsification process during preparation and stabilizing microstructure

of the emulsion during shelf life (Akbari and Nour 2018)

In this project in order to provide standards for the formulation bio creams

containing different concentrations of biosurfactants such as sophorolipids (SLs)

and mannosylerythritol lipids (MELs) mimic creams were prepared consisting of

different concentrations of sodium lauryl ether sulfate (SLES) cetyl alcohol (CA)

and glycerol monostearate (GM) with mixed paraffin oils (white soft paraffin and

light liquid paraffin) in water As a result creams containing 6 wt CA and 2 wt

GM incorporating with varied concentrations of SLES were selected as standards

for bio-cream formulation by replacing SLES with SLs and MELs respectively SLs

that produced by cultivating Candida bombicola in the medium containing

rapeseed oil glucose peptone and yeast extract in shake flask fermentation

mixture of diacylated acidic SLs of C181 diacylated acidic SLs with C201 and

diacylated lactonic SLs with C181 was obtained after purification And MELs were

secreted by Pseudozyma aphidis DSM 70725 and mainly MEL-A was isolated

SLES as an anionic surfactant played key role in system of mixed paraffin oils in

water without which cream was failed to form a homogenized structure showing

phase separate right after preparation (only 6 wt CA and 2 wt GM applied in

the formulation as surfactant system) From this aspect when 2 wt of SLs was

applied in the system with 6 wt CA and 2 wt GM cream was successfully

formulated with consistent texture although the limiting viscosity and

corresponding yield stress is relatively low compared to the system containing 2

wt SLES instead and a viscous behaviour dominant the system from creep test

results However increasing concentration of SLs led to the formulation of more

desired creams with comparable consistency with mimic cream containing

same concentration of SLES Thus when SLs were applied in the formulation

with mixed paraffin oils in water higher concentration incorporated has

potential to produce creams with desired performance While when 2 wt of

MELs was added to the system with fatty alcohols less viscous product was

formulated with smooth texture and consistency but easier to flow

presenting low limit viscosity and corresponding yield stress which is also

proved with oscillatory sweep and creep

246

test And higher concentration of MELs resulted in a worse cream system Thus

for emulsifying mixed paraffin oils in water MELs was not recommended

incorporating with 6 wt CA and 2 wt GM Modification should be made in

altering surfactant system composition in terms of fatty alcohols Unique molecular

structure of MELs is different from SLES and SLs which possesses one

hydrocarbon chain MELs tend to self-assemble into vesicles (Morita et al 2015)

Besides it is interesting to find that the effect of different concentrations of SLES

on cream performance is the same as that of MELs in this study where 6 wt CA

and 2 wt GM involved in mixed paraffin oilswater system while that was different

from what obtained from SLs This could provide information for optimising the

composition of formulations

Vegetable oils are capable of being the substitute for mixed paraffin oils in order to

prepare ldquogreenerrdquo products No big difference was found when same amount of

coconut oil was applied instead of mixed paraffin oils This may because the

similarity of property between them A frequency sweep indicated that Grsquo values

dependent of frequency of mixed paraffin oils and coconut oil are almost the same

but vegetable shortening exhibiting an extremely high Grsquo compared to coconut oil

and paraffin mixed oils

Apart from composition of formulation manufacturing procedure also greatly

affects cream performance especially cooling process where the microstructure of

semi-solid state was altered from lamellar phase to gel phase reflecting as product

of flexible state to a structured body From this work in the system of 4 wt SLES

6 wt CA and 2 wt GM increasing stirring speed during cooling within 10

minutes resulted in a more viscous and rigid cream while longer stirring duration

at a constant speed of 200 rpm led to a reversed effect And for heating procedure

microstructure of creams remains unchanged after mixing for 3 minutes and the

same droplet size distribution was observed for another 17 minutes However

higher mixing speed help formulating creams with small droplets dispersed in

continuous phase Thus appropriate manufacturing procedure should be

determined in order to achieve specific type of products

Rheology is an effective method for rapidly interpreting the flow behaviours of

cream products In this study rheological parameters were applied as indices for

comparing the performance of creams formulated with different concentrations of

surfactant systems and optimising the composition From non-linear rotational test

the limiting value of viscosity was determined by extrapolation of 1st Newtonian

247

plateau and corresponding yield stress was selected as the initial point of shear

thinning which highly agreed with the consistency and texture of the creams from

observation However compared to rotational test oscillatory sweep test provides

more precise explanation of material response to tiny disturbance such as zero

shear viscosity where the microstructure is not fully destroyed As achieved from

this study storage modulus Grsquo presenting as solid domain behaviours positively

supported results from steady state shear along with loss modulus Grsquorsquo Similar to

oscillatory sweep creep test is applied for viscoelastic behaviour determination

provided same results as frequency sweep did but more sophisticated and time-

consuming However it is applicable for the material showing delayed elasticity

that cannot be predicted with the help complex modulus G (Shibaev et al 2019)

To summarize sophorolipids (SLs) mixture of lactonic and acidic forms that

produced by cultivating Candida bombicola consuming glucose and rapeseed oil

as substrates is promising for cream formulation in replacement of same amount

of anionic surfactant (sodium lauryl ether sulfateSLES) incorporating with cetyl

alcohol (CA) and glycerol monostearate (GM) in mixed paraffin oils and water

system Better performance of cream (appropriate stiffness with consistent texture)

could be realized when higher concentration of SLs is involved However for

mannosylerythritol lipids (MELs) (mainly MEL-A) that originated from Pseudozyma

aphidis DSM 70725 growing in the medium containing glucose and rapeseed less

structured creams with higher mobility were produced and higher concentration of

MELs incorporated more dissatisfactory cream tends to be produced Coconut oil

is a potential substitute for mixed paraffin oils in cream formulation However

although same amount of coconut oils applied in the formulation is able to produce

cream-like products the texture and morphology may not be satisfied when same

manufacturing procedure was applied as that for mixed paraffin oils included and

further modification of the formulae composition should also be taken into account

Vegetable shortening may need pre-treatment or further modification for

eliminating undesired colour and granular texture of cream

Still further study could be conducted for improving and perfecting this project

1 The interfacial tension of the surfactant system is worth of analysing Because

mixture of liquid paraffin and white soft paraffin is not in liquid state at room

temperature silicon oil could be an alternative for the study As suggested 0 wt

2 wt 4 wt 6 wt and 10 wt of SLES solution could be prepared After

obtaining the dependence of interfacial tension on SLES concentration different

248

concentration of cetyl alcohol could be added into silicon oil to get the

measurement of the interfacial tension between silicon oil (with cetyl alcohol) and

SLES solution

2 Emulsification Index (EI) measurement should be carried out for understanding

the emulsifying property of SLES Two types of oils could be used in the

measurement silicon oil and the mixture of two paraffin oils Equal volume of oil is

mixed with different concentrations of SLES solutions (0 wt 2 wt 3 wt 4 wt

6 wt) followed by a vortex for 2 min After standing for 24 h EI could be

calculated The measurement could also be conducted at different temperatures

for example 25plusmn2 degC 40plusmn2 degC 55plusmn2 degC and 70plusmn2 degC

3 Rheological measurement should take more caution of wall depletion which may

lead to inaccurate characterisation of actual flow property of materials although it

is very common and as a matter of fact that it cannot be fully eliminated However

in this project all characterisations of creams were consistently applied 40 mm

cone-plate geometry with a measuring gap of 57 mm and results was not largely

discrepant with that obtained from literatures where a limiting viscosity of 104 Pas

for a cream and 103 Pas for a lotion (Kwak et al 2015) And the values of yield

stress were reasonable which line in between 10 Pa and 100 Pa Even though in

order to further investigate the effect degree of wall slip on the results a geometry

with roughed surface is suggested and different size of geometry and mearing gap

are worth of trying with

4 Further purification of biosurfactants is necessary as biosurfactants applied in

the formulation were mixtures of different structures and forms Large effect may

arise on cream performance when surfactants with structural differences are

applied Thus structural separation of SLs and MELs could help investigate effect

of biosurfactants with unique structure on cream formulation

5 When reliable results were obtained in lab scale enlarging formulation scale in

a pilot scale is suggested for better understanding influences of manufacturing

process on cream production and optimizing lab-scaled results From this aspect

economic friendly biosurfactants production with higher yield is required for

facilitating the commercialization of bio-cream production in lab-scaled research

249

References Ade-Browne C Mirzamani M Dawn A Qian S Thompson R Glenn R amp Kumari H

2020 Effect of ethoxylation and lauryl alcohol on the self-assembly of sodium laurylsulfate Significant structural and rheological transformation Colloids and Surfaces A Physicochemical and Engineering Aspects 124704

Adu S A Naughton P J Marchant R amp Banat I M 2020 Microbial Biosurfactants in Cosmetic and Personal Skincare Pharmaceutical Formulations Pharmaceutics 12 1099

Agneta M Zhaomin L Chao Z amp Gerald G 2019 Investigating synergism and antagonism of binary mixed surfactants for foam efficiency optimization in high salinity Journal of Petroleum Science amp Engineering 175 489-494

Agrawal N Maddikeri G L amp Pandit A B 2017 Sustained release formulations of citronella oil nanoemulsion using cavitational techniques Ultrasonics Sonochemistry 36 367-374

Ahmadi-Ashtiani H R Baldisserotto A Cesa E Manfredini S amp Vertuani S 2020 Microbial Biosurfactants as Key Multifunctional Ingredients for Sustainable Cosmetics

Ahmadi D Mahmoudi N Li P Tellam J Barlow D amp Lawrence M J 2020 Simple creams complex structures Molecular Assemblies Characterization and Applications ACS Publications

Ahmed T M 2019 Fatigue performance of hot mix asphalt tested in controlled stress mode using dynamic shear rheometer International Journal of Pavement Engineering 20 255-265

Aiza Gay Corpuz Priyabrata Pal Fawzi amp Banat] 2019 Effect of temperature and use of regenerated surfactants on the removal of oil from water using colloidal gas aphrons Separation amp Purification Technology

Akbari S amp Nour A H 2018 Emulsion types stability mechanisms and rheology A review International Journal of Innovative Research and Scientific Studies 1 14-21

Ali Ebadi Nayer Azam Khoshkholgh Sima Mohsen Olamaee Maryam amp Hashemi 2017 Effective bioremediation of a petroleum-polluted saline soil by a surfactant-producing Pseudomonas aeruginosa consortium Journal of Advanced Research

Ali M F Amin D amp Reza S S 2018 An investigation into surfactant flooding and alkaline-surfactant-polymer flooding for enhancing oil recovery from carbonate reservoirs Experimental study and simulation Energy Sources Part A Recovery Utilization amp Environmental Effects 40 1-12

Almeira N Komilis D Barrena R Gea T amp Saacutenchez A 2015 The importance of aeration mode and flowrate in the determination of the biological activity and stability of organic wastes by respiration indices Bioresource technology 196 256-262

Alsinan M Kwak H Marques D S amp Kaidar Z Identifying High-Performance EOR Surfactants Through Non-Destructive Evaluation of the Phase Behavior Microstructure SPEIATMI Asia Pacific Oil amp Gas Conference and Exhibition 2019

Ananthapadmanabhan K 2019 Amino-Acid Surfactants in Personal Cleansing Tenside Surfactants Detergents 56 378-386

Anburajan L Meena B Raghavan R V Shridhar D Joseph T C Vinithkumar N V Dharani G Dheenan P S amp Kirubagaran R 2015 Heterologous expression purification and phylogenetic analysis of oil-degrading biosurfactant biosynthesis genes from the marine sponge-associated Bacillus licheniformis NIOT-06 Bioprocess and Biosystems Engineering 38 1009-1018

250

Ankulkar R amp Chavan M 2019 Characterisation and Application Studies of Sophorolipid Biosurfactant by Candida tropicalis RA1 Journal of Pure and Applied Microbiology 13 1653-1665

Arauacutejo J S d 2018 Produccedilatildeo de ramnolipiacutedeos por Pseudomonas aeruginosa AP029-GLVIIA usando glicose como substrato e aplicaccedilotildees Brasil

Arias A Macorra J C Govindjee S amp Peters O A 2018 Correlation between temperature-dependent fatigue resistance and differential scanning calorimetry analysis for 2 contemporary rotary instruments Journal of endodontics 44 630-634

Ashby R D amp Solaiman D K 2019 Sophorolipids Unique microbial glycolipids with vast application potential Microbial Biosurfactants and their Environmental and Industrial Applications CRC Press

Aswal A Kalra M amp Rout A 2013 Preparation and evaluation of polyherbal cosmetic cream Der Pharmacia Lettre 5 83-88

Awad T S Johnson E S Bureiko A amp Olsson U 2011 Colloidal Structure and Physical Properties of Gel Networks Containing Anionic Surfactant and Fatty Alcohol Mixture Journal of Dispersion Science and Technology 32 807-815

Bages-Estopa S White D Winterburn J Webb C amp Martin P 2018 Production and separation of a trehalolipid biosurfactant Biochemical Engineering Journal 139 85-94

Bai L amp McClements D J 2016 Formation and stabilization of nanoemulsions using biosurfactants Rhamnolipids Journal of colloid and interface science 479 71-79

Ballmann C amp Muumleller B 2008 Stabilizing Effect of Cetostearyl Alcohol and Glycerylmonstearate as Co-emulsifiers on Hydrocarbon-free OW Glyceride Creams Pharmaceutical development and technology 13 433-445

Ban T Kawaizumi F Nii S amp Takahashi K 2000 Study of drop coalescence behavior for liquidndashliquid extraction operation Chemical engineering science 55 5385-5391

Banat I M Franzetti A Gandolfi I Bestetti G Martinotti M G Fracchia L Smyth T J amp Marchant R 2010 Microbial biosurfactants production applications and future potential Applied microbiology and biotechnology 87 427-444

Banerjee K Thiagarajan N amp Thiagarajan P 2019 Formulation and characterization of a Helianthus annuus‐alkyl polyglucoside emulsion cream for topical applications

Journal of cosmetic dermatology 18 628-637 Bang J-H Song K S Lee M G Jeon C W amp Jang Y N 2010 Effect of critical micelle

concentration of sodium dodecyl sulfate dissolved in calcium and carbonate source solutions on characteristics of calcium carbonate crystals Materials transactions 1007121124-1007121124

Bankole M T Abdulkareem S A Tijani J O Ochigbo S S amp Roos W D 2017 Chemical oxygen demand removal from electroplating wastewater by purified and polymer functionalized carbon nanotubes adsorbents Water Resources amp Industry 18 33-50

Barnes H A 1995 A review of the slip (wall depletion) of polymer solutions emulsions and particle suspensions in viscometers its cause character and cure Journal of Non-Newtonian Fluid Mechanics 56 221-251

Barnes H A Hutton J F amp Walters K 1989 An introduction to rheology Elsevier Beck A Werner N amp Zibek S 2019 Mannosylerythritol Lipids Biosynthesis Genetics

and Production Strategies Biobased Surfactants Elsevier Bekker M Webber G amp Louw N 2013 Relating rheological measurements to primary

and secondary skin feeling when mineral‐based and FischerndashTropsch wax‐based

251

cosmetic emulsions and jellies are applied to the skin International Journal of Cosmetic Science 35 354-361

Bera A Ojha K amp Mandal A 2013 Synergistic Effect of Mixed Surfactant Systems on Foam Behavior and Surface Tension Journal of Surfactants amp Detergents 16 621-630

Bertin H Estrada E D C amp Atteia O 2017 Foam placement for soil remediation Environmental Chemistry 14

Bezerraa K G Durvala I J Silvab I A amp CG F 2020 Emulsifying Capacity of Biosurfactants from Chenopodium Quinoa and Pseudomonas Aeruginosa UCP 0992 with Focus of Application in the Cosmetic Industry CHEMICAL ENGINEERING 79

Bharali P Singh S P Dutta N Gogoi S Bora L Debnath P amp Konwar B K 2014 Biodiesel derived waste glycerol as an economic substrate for biosurfactant production using indigenous Pseudomonas aeruginosa RSC advances 4 38698-38706

Bhattachar S N Risley D S Werawatganone P amp Aburub A 2011 Weak bases and formation of a less soluble lauryl sulfate saltcomplex in sodium lauryl sulfate (SLS) containing media International journal of pharmaceutics 412 95-98

Bhosale S S Rohiwal S S Chaudhary L S Pawar K D Patil P S amp Tiwari A P 2019 Photocatalytic decolorization of methyl violet dye using Rhamnolipid biosurfactant modified iron oxide nanoparticles for wastewater treatment Journal of Materials Science Materials in Electronics 30 4590-4598

Blanco-Diacuteaz E Castrejoacuten-Gonzaacutelez E Rico-Ramiacuterez V Aztatzi-Pluma D amp Diacuteaz-Ovalle C 2018 Polydispersity influence in rheological behavior of linear chains by molecular dynamics Journal of Molecular Liquids 268 832-839

Bnyan R Khan I Ehtezazi T Saleem I Gordon S Neill F O amp Roberts M 2018 Surfactant Effects on Lipid-Based Vesicles Properties Journal of Pharmaceutical Sciences S0022354918300054

Bonnin L 2019 Optimization of stability and rheological robustness of cosmetic salt-containing lamellar gel phase emulsions

Borah S N Sen S Goswami L Bora A Pakshirajan K amp Deka S 2019 Rice based distillers dried grains with solubles as a low cost substrate for the production of a novel rhamnolipid biosurfactant having anti-biofilm activity against Candida tropicalis Colloids and Surfaces B Biointerfaces 182 110358

Boxall J A Koh C A Sloan E D Sum A K amp Wu D T 2010 Measurement and calibration of droplet size distributions in water-in-oil emulsions by particle video microscope and a focused beam reflectance method Industrial amp engineering chemistry research 49 1412-1418

Boxall J A Koh C A Sloan E D Sum A K amp Wu D T 2012 Droplet size scaling of water-in-oil emulsions under turbulent flow Langmuir 28 104-110

Boyer H C Bzdek B R Reid J P amp Dutcher C S 2017 Statistical thermodynamic model for surface tension of organic and inorganic aqueous mixtures The Journal of Physical Chemistry A 121 198-205

Brummer R 2013 Rheology of Cosmetic Emulsions Product Design and Engineering Formulation of Gels and Pastes 51-74

Bunet R Riclea R Laureti L Hotel L Paris C Girardet J-M Spiteller D Dickschat J S Leblond P amp Aigle B 2014 A single Sfp-type phosphopantetheinyl transferase plays a major role in the biosynthesis of PKS and NRPS derived metabolites in Streptomyces ambofaciens ATCC23877 PLoS One 9 e87607

Caffalette C A Kuklewicz J Spellmon N amp Zimmer J 2020 Biosynthesis and export of bacterial glycolipids Annual review of biochemistry 89 741-768

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Calero N Muntildeoz J Cox P W Heuer A amp Guerrero A 2013 Influence of chitosan concentration on the stability microstructure and rheological properties of OW emulsions formulated with high-oleic sunflower oil and potato protein Food Hydrocolloids 30 152-162

Callaghan B Lydon H Roelants S L Van Bogaert I N Marchant R Banat I M amp Mitchell C A 2016 Lactonic Sophorolipids increase tumor burden in Apcmin+-mice PloS one 11 e0156845

Callow N V Ray C S Kelbly M A amp Ju L-K 2016 Nutrient control for stationary phase cellulase production in Trichoderma reesei Rut C-30 Enzyme and microbial technology 82 8-14

Cacircmara J Sousa M Neto E B amp Oliveira M 2019 Application of rhamnolipid biosurfactant produced by Pseudomonas aeruginosa in microbial-enhanced oil recovery (MEOR) Journal of Petroleum Exploration and Production Technology 9 2333-2341

Cantero del Castillo J 2019 Development of functional facial creams and their manufacturing process

Canu R Puggelli S Essadki M Duret B Menard T Massot M Reveillon J amp Demoulin F 2018 Where does the droplet size distribution come from International Journal of Multiphase Flow 107 230-245

Caracciolo A B Cardoni M Pescatore T amp Patrolecco L 2017 Characteristics and environmental fate of the anionic surfactant sodium lauryl ether sulphate (SLES) used as the main component in foaming agents for mechanized tunnelling Environmental Pollution 226 94-103

Caritaacute A C de Azevedo J R Buri M V Bolzinger M-A Chevalier Y Riske K A amp Leonardi G R 2020 Stabilization of vitamin C in emulsions of liquid crystalline structures International Journal of Pharmaceutics 120092

Castellano S Carrillo L Sheibat-Othman N Marchisio D Buffo A amp Charton S 2019 Using the full turbulence spectrum for describing droplet coalescence and breakage in industrial liquid-liquid systems Experiments and modeling Chemical Engineering Journal 374 1420-1432

Chayabutra C amp Ju L K 2001 Polyhydroxyalkanoic acids and rhamnolipids are synthesized sequentially in hexadecane fermentation by Pseudomonas aeruginosa ATCC 10145 Biotechnology progress 17 419-423

Chebbi A Hentati D Zaghden H Baccar N Rezgui F Chalbi M Sayadi S amp Chamkha M 2017 Polycyclic aromatic hydrocarbon degradation and biosurfactant production by a newly isolated Pseudomonas sp strain from used motor oil-contaminated soil International Biodeterioration amp Biodegradation 122 128-140

Chellapa P Ariffin F D Eid A M Almahgoubi A A Mohamed A T Issa Y S amp Elmarzugi N A 2016 Nanoemulsion for cosmetic application European Journal of Biomedical and Pharmaceutical Sciences 3 8-11

Chen W Qu Y Xu Z He F Chen Z Huang S amp Li Y 2017a Heavy metal (Cu Cd Pb Cr) washing from river sediment using biosurfactant rhamnolipid Environmental Science and Pollution Research 24 16344-16350

Chen X Feng Q Liu W amp Sepehrnoori K 2017b Modeling preformed particle gel surfactant combined flooding for enhanced oil recovery after polymer flooding Fuel 194 42-49

Chizawa Y Miyagawa Y Yoshida M amp Adachi S 2019 Effect of crystallization of oil phase on the destabilization of OW emulsions containing vegetable oils with low melting points Colloids and Surfaces A Physicochemical and Engineering Aspects 582 123824

253

Choi B Loh X J Tan A Loh C K Ye E Joo M K amp Jeong B 2015 Introduction to in situ forming hydrogels for biomedical applications In-Situ Gelling Polymers Springer

Chrzanowski Ł Ławniczak Ł amp Czaczyk K 2012 Why do microorganisms produce rhamnolipids World Journal of Microbiology and Biotechnology 28 401-419

Ciesielska K Roelants S L Van Bogaert I N De Waele S Vandenberghe I Groeneboer S Soetaert W amp Devreese B 2016 Characterization of a novel enzymemdashStarmerella bombicola lactone esterase (SBLE)mdashresponsible for sophorolipid lactonization Applied microbiology and biotechnology 100 9529-9541

Coelho A L S Feuser P E Carciofi B A M de Andrade C J amp de Oliveira D 2020 Mannosylerythritol lipids antimicrobial and biomedical properties Applied Microbiology and Biotechnology 104 2297-2318

Cohen L Martin M Soto F Trujillo F amp Sanchez E 2016 The effect of counterions of linear alkylbenzene sulfonate on skin compatibility Journal of Surfactants and Detergents 19 219-222

Colafemmina G Palazzo G Mateos H Amin S Fameau A-L Olsson U amp Gentile L 2020a The cooling process effect on the bilayer phase state of the CTACcetearyl alcoholwater surfactant gel Colloids and Surfaces A Physicochemical and Engineering Aspects 124821

Colafemmina G Palazzo G Mateos H Amin S amp Gentile L 2020b The cooling process effect on the bilayer phase state of the CTACcetearyl alcoholwater surfactant gel Colloids and Surfaces A Physicochemical and Engineering Aspects 597 124821

Colo S M Herh P K Roye N amp Larsson M 2004 Rheology and the texture of pharmaceutical and cosmetic semisolids American Laboratory 36 26-35

Coronel Leoacuten J Manresa Presas M amp Marqueacutes Villavecchia A M 2016 Lichenysin production and application in the pharmaceutical field Recent Advances in Pharmaceutical Sciences VI 2016 Research Signpost Editors Diego Muntildeoz Torrero Agravengela Domiacutenguez Garciacutea amp Ma Aacutengeles Manresa Presas ISBN 978-81-308-0566-5 Chapter 9 p 147-163

Coussot P 2005 Rheometry of pastes suspensions and granular materials applications in industry and environment John Wiley amp Sons

Da Costa F Le Grand F Queacutereacute C Bougaran G Cadoret J P Robert R amp Soudant P 2017 Effects of growth phase and nitrogen limitation on biochemical composition of two strains of Tisochrysis lutea Algal research 27 177-189

da Rocha Junior R B Meira H M Almeida D G Rufino R D Luna J M Santos V A amp Sarubbo L A 2019 Application of a low-cost biosurfactant in heavy metal remediation processes Biodegradation 30 215-233

Dalili D Amini M Faramarzi M A Fazeli M R Khoshayand M R amp Samadi N 2015 Isolation and structural characterization of Coryxin a novel cyclic lipopeptide from Corynebacterium xerosis NS5 having emulsifying and anti-biofilm activity Colloids and Surfaces B Biointerfaces 135 425-432

Damasceno F R Cavalcanti-Oliveira E D Kookos I K Koutinas A A Cammarota M C amp Freire D M 2018 Treatment of wastewater with high fat content employing an enzyme pool and biosurfactant technical and economic feasibility Brazilian Journal of Chemical Engineering 35 531-542

Danley R L 2002 Power compensation differential scanning calorimeter Google Patents Dao H Lakhani P Police A Kallakunta V Ajjarapu S S Wu K-W Ponkshe P Repka

M A amp Murthy S N 2018 Microbial stability of pharmaceutical and cosmetic products Aaps Pharmscitech 19 60-78

254

Das A J amp Kumar R 2019 Production of biosurfactant from agro-industrial waste by Bacillus safensis J2 and exploring its oil recovery efficiency and role in restoration of diesel contaminated soil Environmental Technology amp Innovation 16 100450

Dashtaki S R M Ali J A Manshad A K Nowrouzi I amp Keshavarz A 2020 Experimental investigation of the effect of Vitagnus extract on enhanced oil recovery process using interfacial tension (IFT) reduction and wettability alteration mechanisms Journal of Petroleum Exploration amp Production Technology

Daverey A amp Pakshirajan K 2009 Production characterization and properties of sophorolipids from the yeast Candida bombicola using a low-cost fermentative medium Applied biochemistry and biotechnology 158 663-674

Daverey A amp Pakshirajan K 2010 Sophorolipids from Candida bombicola using mixed hydrophilic substrates production purification and characterization Colloids and Surfaces B Biointerfaces 79 246-253

David O A David D O Mogoase C Popescu L C Giosan C amp Pellegrino A 2019 Psychological effects and brain correlates of a rose‐based scented cosmetic

cream Journal of Sensory Studies 34 e12536 de Almeida D G Brasileiro P P F Rufino R D de Luna J M amp Sarubbo L A 2019

Production formulation and cost estimation of a commercial biosurfactant Biodegradation 30 191-201

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de Freitas Ferreira J Vieira E A amp Nitschke M 2019 The antibacterial activity of rhamnolipid biosurfactant is pH dependent Food Research International 116 737-744

De Souza P M Andrade Silva N R Souza D G Lima e Silva T A Freitas-Silva M C Andrade R F Silva G K Albuquerque C D Messias A S amp Campos-Takaki G M 2018 Production of a Biosurfactant by Cunninghamella echinulata using renewable substrates and its applications in enhanced oil spill recovery Colloids and Interfaces 2 63

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Guzmaacuten E Llamas S Fernaacutendez-Pentildea L Leacuteonforte F Baghdadli N Cazeneuve C Ortega F Rubio R G amp Luengo G S 2020 Effect of a natural amphoteric surfactant in the bulk and adsorption behavior of polyelectrolyte-surfactant mixtures Colloids and Surfaces A Physicochemical and Engineering Aspects 585 124178

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Haloi S Sarmah S Gogoi S B amp Medhi T 2020 Characterization of Pseudomonas sp TMB2 produced rhamnolipids for ex-situ microbial enhanced oil recovery 3 Biotech 10 1-17

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Hiraoka K 2013 Fundamentals of mass spectrometry Houmlhne G Hemminger W F amp Flammersheim H-J 2013 Differential scanning

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Droplet size rheological behavior zeta-potential and creaming index Journal of Industrial and Engineering Chemistry 67 123-131

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Huang J amp Ren Z H 2020 Mechanism on micellization of amino sulfonate amphoteric surfactant in aqueous solutions containing different alcohols and its interfacial adsorption Journal of Molecular Liquids 316 113793

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Joshi-Navare K Khanvilkar P amp Prabhune A 2013 Jatropha oil derived sophorolipids production and characterization as laundry detergent additive Biochemistry research international 2013

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Kreling N Zaparoli M Margarites A Friedrich M Thom eacute A amp Colla L 2020

Extracellular biosurfactants from yeast and soilndashbiodiesel interactions during bioremediation International Journal of Environmental Science and Technology 17 395-408

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Langenbucher F amp Lange B 1970 Prediction of the application behaviour of cosmetics from rheological measurements Pharm Acta Helv 45 572-82

Langley C A amp Belcher D 2012 Pharmaceutical Compounding and Dispensing Pharmaceutical Press

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Li J Li H Li W Xia C amp Song X 2016 Identification and characterization of a flavin-containing monooxygenase MoA and its function in a specific sophorolipid molecule metabolism in Starmerella bombicola Applied microbiology and biotechnology 100 1307-1318

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Li T Wang Y amp Dong Y 2012 Effect of solid contents on the controlled shear stress rheological properties of different types of sludge Journal of Environmental Sciences 24 1917-1922

Li Y Hu J Liu H Zhou C amp Tian S 2020 Electrochemically reversible foam enhanced flushing for PAHs-contaminated soil Stability of surfactant foam effects of soil factors and surfactant reversible recovery Chemosphere 260

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Lima F A Santos O S Pomella A W V Ribeiro E J amp de Resende M M 2020 Culture Medium Evaluation Using Low‐Cost Substrate for Biosurfactants Lipopeptides

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Potential application of a multifunctional biosurfactant extract obtained from corn as stabilizing agent of vitamin C in cosmetic formulations Sustainable Chemistry and Pharmacy 16 100248

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Santos W M de Caldas Nobre M S Cavalcanti M T dos Santos K M O Salles H O amp Alonso Buriti F C 2019 Proteolysis of reconstituted goat whey fermented by Streptococcus thermophilus in co ‐ culture with commercial probiotic

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274

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275

Sobrinho H Luna J M Rufino R D Porto A amp Sarubbo L A 2013 Biosurfactants classification properties and environmental applications Recent developments in biotechnology 11 1-29

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1

Table of Contents

Chapter 1 Introduction 17

11 Research System 17

12 Research Motivation 18

13 State-of-the-Art 19

14 Research Objectives and Aims 30

15 Overview of Thesis 30

16 Nomenclature 31

Chapter 2 Literature Review 32

21 Surfactants 32

211 Structure of Surfactants 33

212 Classification of Surfactants 33

213 Surfactant Behaviour in Water Solution 39

22 Bio-surfactants 44

221 Classification of Biosurfactants (BSs) 45

222 The Production and Extraction of Biosurfactants (BSs) 46

223 Characterization of Biosurfactants (BSs) 48

224 Application of Biosurfactants (BSs) in Various Fields 49

225 Potential Cosmetic-applicable Biosurfactants (BSs) 51

23 Emulsion 65

231 Overview of Emulsion 66

232 Emulsion Formation 66

233 Mechanisms of Emulsion Instability 73

24 Rheology 75

241 Rheology of Emulsions 75

242 Rheometry and Rheometers 77

Chapter 3 Materials and Methodology 81

31 Sophorolipids (SLs) Production 81


312 Chemicals 81


32 Mannosylerythritol Lipids (MELs) Production 84

2


322 Chemicals 84








90

341 Chemicals 90

342 Recipes 90






Procedure 98


Procedure 99



361 Rheology 101



364 Microscopy 132



MS) 136








3






System 158







161



163


Formulation_Ⅰ 180



Formulation_Ⅱ 184




188


192










4






System 210










References 249

5

List of Figures




water surface 39







89
























profile 114






122



6


particles 126





size classes 128


unit 130





view (right) 135








145







stress of 4 Pa 152



154












300 Pa 164

7


































software) 183










8







193










100 Hz 197






spectrometry 202




fermentation 204



from 600 to 750 205













9





















water system 222























10










































water system 240



water system 241

11







12

List of Tables



















alcohols 92


system 94











100



2020 105






13


140




142






















specified 194




14

Abstract



































15

Declarations













copies made















16

Acknowledgements












17


11 Research System






















c Bulk water











18












products











ingredients Weight

concentration (wt)

function




lanolin 10





Sodium Hydroxide




Purified water

19




















13 State-of-the-Art
















20





































21





































22
















Lin et al 2016b)


















2020)

23





































24





































25





































26




































27




































28



(Lukic et al 2016)

















formulations

















29





































30

























their structure




cream performance




31









16 Nomenclature




Cetyl alcohol CA


Sophorolipids SLs


Biosurfactants BSs

32




rheology

21 Surfactants


















surf

ace

ten

sio

in


surfactant solutes



33


Shah 2013)
















et al 2016)







Hydrophilic head

(Polar)



34


in Table 21


Name and Structure

Stearalkonium

Chloride

Cetrimonium

Chloride

Dicetyldimonium

Chloride




















35











representatives








Carboxylates

(-COOM)

Sodium Stearate

C17H35-COO--Na+

Sulfonates

(-SO3M)


C18H29-SO3--Na+

Sulfate

esters

(-OSO3M)


C16H33-O-SO3--2Na+

36





et al 2017b)






























37


et al 2012)

















Name and Structure

Cetyl

alcohol

Glycerol

mono-

stearate

Sorbian

mono-

stearate

(Span 60)


(Tween 60)

38



























2020)

39





2131 Monomers














(Rehman et al 2017)



air

water

a) cationic

b) anionic

c) Non-ionic

d) Amphoteric



40











2132 Micelles
























41





























42




















Tem

pe

ratu

re H

igh


Critical

Micelle

Concentrati

on (CMC)


Molecular

soluble phase

Krafft

Point

So

lid

Are

a

Micelle Solution


Area

Middle Phase

(Hexagon

form)

Lamellar

Phase

Cubic

Phase

Tc boundary

Cloud Point

boundary

Liquid-liquid

phase Separation

Spheric

Micelle

s

Rodlike

Micelle

s


43
















44

22 Bio-surfactants




































45









2016)











Low mass BSs

Glycolipids



Trehalolipids

Lipopeptides and

lipoprotein


Polymyxin



High mass BSs




Wholecells




46




































47






































48



































49








2016)





















et al 2019)







50





































51




































52





































53



































54
















enhanced


55

























Acidic Sophorolipid


56

















a) Substrates



















57


et al 2019)

































58




































59





































60


















61






















O O

CH2

C

C

CH2

OH

OH

H

H OR1

CH3

CH3

R2

O


R2=H MEL-D R1=R2=H


62

































2020)

63





































64




































65
























Beck et al 2019)

23 Emulsion







2019)

66


































67
















(Wang et al 2018b)

∆119875119871 =4120574

11988922














68



































69















31186~32865 mN m-1 (Ibrahim et al 2015)





















70




































71


al 2016)




























(Krasinski 2013)

120578119888119900119886119897 = exp (minus119905119889

119905119888) 23



72















119889119898119894119899311 =

120574138119861046

00272120583119888120588119888084휀089

24


















73



































74







V =1198632(120588119878 minus 120588119874)119892

1812057825













Good emulsion


Creaming Breaking


75

24 Rheology

































76









ṙ =V

h26




Lange 1970)



calculation

Calculation

values of shear

rate

ṙ (s-1)


Velocity 2cms

1

Rubbing on

the skin



extending 24 cms

120



extending 10 cms

100



extending 10 cms

103



extending 10 cms

104





77




































78





































79















2002)






















80








Stern 2011)



























81





methods








-80 degC

312 Chemicals














2019)




82



al 2019)

















2019)















83















Equation 31

1198821 minus 11988210

119881times 100 31

















84


(Dolman et al 2017)














for further use

322 Chemicals







Hexane

Parameters Input




20 to 70



Wavelength of UV

Detector

207

85


































86















3311 Chemicals




formulation

3312 Recipes



Table 32



(wt)

Mass

(g)

Oil Phase (A)

White soft paraffin


Cetyl alcohol

145

126

12

58

504

48

Aqueous Phase (B)

Deionized water

609

2346


87





mixing


















water





3321 Chemicals





88

3322 Recipes



Table 33










England LTD)


(wt)

Mass

(g)

Oil Phase (A)

White soft paraffin


Cetyl alcohol

145

126

6

58

504

24

Aqueous Phase (B)

Deionized water

SLES

609

2346

6 24


NA

89


















water

Oil

phase

Aqueous

phase


90


Cream Formulation









341 Chemicals










Phases Components



Block

Emulsifying system



monostearate



342 Recipes




91











preservatives


surfactant system






Mimic Creams


Component (wt)

White soft paraffin

145 145 145 145


126 126 126 126

SLES 0 2 4 6 0 2 4 6 0 2 4 6 0 2 4 6

Cetyl Alcohol (CA)

6 6 2 2


(GM) 6 2 6 2


Residuals 5

92




fatty alcohols




















Mimic Creams

Ingredients F5 F6

Component (wt)



SLES 2 4

CA 5 6 7 5 6 7

GM 2 2


residuals 5

93



94








CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2








CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2








CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2


95










cold tap water















96










Ingredients


White Soft Paraffin


Cetyl Alcohol (CA)


Deionized Water


(SLES)

Water Tap

Water

Bath

D

H

T

Parameters Values

D (mm)

H (mm)

T (mm)

60

137

70

Clam

p

Clamp

Clam

p

Clamp

(b)

(a) (c)

(d)

Storage

Sink



97








cylinder was added



















temperature










98



39



Heating Procedure


















Component


(wt)


(wt)


(wt)



126 126 126

SLES 2 4 6

CA 6 6 6

GM 2 2 2

Residules

(not in the

formulation)

5 5 5


99


was set at 200 rpm

















procedure









Cream Sample

Mixing Procedure

Mixing Speed

(rpm)

Mixing Duration

(min)

A

500

3

B 5

C 10

D 15

E 20

100

















Cream Sample

Mixing Procedure

Mixing Speed

(rpm)

Mixing Duration

(min)

A 500

10 B 700

C 900

Cream


Mixing Speed

(rpm)

Mixing Duration

(min)

Stirring speed

(rpm)

Cooling Duration

(min)

A

500

10

200 10

B 0 10

C 300 10

D 200 5

E 200 20

101


analysis

361 Rheology


















Equation 32

120591 =119865

11986032




120574 =∆119909

∆11991033


two plates



velocity u

102

=119889120574

119889119905=

119889

119889119905(

119889119909

119889119910) =

119889

119889119910(

119889119909

119889119905) =

119889119906

11988911991034




35 and 36

120591 = minus120583 (119889119906

119889119910) 35

120583 =120591

36








() (Mezger 2020)

120591 = minus120578 (119889119906

119889119910) 37


103










Pure viscous

fluid

Time independent

Newtonian fluid


Non-Newtonian fluid



Time dependent

Thixotropic fluid

Rheopectic fluid



104























105


starts to alter






in Figure 35



Bingham Model






above yield point

120636119942119943119943 = 120636119942119943119943infin +120649119962

Where





Model

120636119942119943119943 = 119948(119931) ∙ 119951minus120783

Where

119897119900119892 or 119897119900119892120591

119897119900119892

120578

1st Newtonian

Plateau


1205780

120578infin


Ellis model

Sisko model


106



119949119952119944120636 minus 119949119952119944120649 curve


plateau





power law model






above yield point

120649 = 120649119962 + 119948(119931) ∙ 119951

Where











the transient area



120578119890119891119891() minus 120578infin

1205780 minus 120578infin= (1 + |120582 ∙ |119886)

119899minus1119886


∙ (1 + |120582 ∙ |119886)119899minus1

119886

Where







as follow

120636119942119943119943() =120636120782

(120783 + |120640 ∙ |119938)119951minus120783

119938

Cross Model




120578119890119891119891() minus 120578infin

1205780 minus 120578infin=

1

1 + (119870 ∙ )1minus119899

Where


107


119949119952119944 curve




120636119942119943119943() =120636120782

120783 + (120636120782 ∙

120649lowast )120783minus119951


119870frasl

Ellis Model






region

120636119942119943119943() =120636120782

120783 + (120649

120649120783120784frasl

)

120630minus120783

Where



120578119890119891119891 decreased to 120578119890119891119891

2frasl


Sisko Model






region

120636119942119943119943() = 119922 ∙ 119951minus120783 + 120636infin

Where













108










Shea

r st

ress

120591

Shear rate

Thixotropic fluid

Rheopectic fluid

Fτ

Fτ

Δx

Δx



109

120590119866 = E ∙ ε119866 38


120591120578 = 120578 ∙119889120574120578

119889119905= 120578 ∙ 120578 39






119864frasl




=1205910










dγ119905119900119905119886119897

dt=

1

119864∙

dτ119905119900119905119886119897

dt+

120591119905119900119905119886119897

120578310



τ

t t0=0 t1

τ

0

a ε

t t0=0 t1

1205980 1205980 =

1205910119864frasl

b γ

t t0=0 t1

γ

0

1205740 =1205910

120578(1199051 minus 1199050)

c


110

















ε

t t0=0 t1

휀0

b

휀0

τ

t t0=0 t1

τ0

a

휀1

휀1

η η

F F

η

E

∆119909120578

∆119909119864 F

t=T t=T t=T+ΔT

E E 120591119866 = E ∙ ε119866

120591120578 = 120578 ∙119889120574120578

119889119905



111

119889γ119905119900119905119886119897

119889119905=

120591119905119900119905119886119897

120578minus

E

120578∙ γ119905119900119905119886119897 311













is 120649120782





120574120578

120591120578 = 120578 ∙119889120574120578

119889119905

γ119866

120591119866 = G ∙ γ119866

F 120591119905119900119905119886119897


112

Burgers Model
















120574

t t0 t1

b τ

t t0=0 t1

τ0

a

F τtotal

E3

Ⅲ

η2

Ⅱ E1

Ⅰ

η4

Ⅳ

120598

t

t0 t1

E1_R

E3 η2_C

η

4

E1_C

E3

η2_R

Creep

strain

Permanent

strain

b) a)



113






119869(119905) =120574(119905)

120591312




log t t0

log c

reep

com

pli

ance

J

Elastic material

Viscous material


114










313 (Mezger 2006)

120574 = 120574119898119886119909 sin 120596119905 = 120574119898119886119909119890119894120596119905 313





120591 = 120591119898119886119909 sin(120596119905 + 120575) = 120591119898119886119909119890119894(120596119905+120575) 314


amplitude



0

deg

90

deg

180

deg

270

deg

360

deg

0deg360

deg

90

deg

180deg

27

0deg

90

deg 27

0deg


115





120575 lt 90deg) (Lade et al 2019)





119866lowast =119888119900119898119901119897119890119909 119904119905119903119890119904119904 119886119898119901119897119894119905119906119889119890

119888119900119898119901119897119890119909 119904119905119903119886119894119899 119886119898119901119897119894119905119906119889119890=

120591119898119886119909120574119898119886119909

frasl 315


the shear strain





these terms

119866prime = 119866lowast cos 120575 =120591119898119886119909

120574119898119886119909cos 120575 316


120574119898119886119909sin 120575 317



119866prime319






120578lowast =119888119900119898119901119897119890119909 119904119905119903119890119904119904 119886119898119901119897119894119905119906119889119890

119888119900119898119901119897119890119909 119904119905119903119886119894119899 119903119886119905119890 119886119898119901119897119894119905119906119889119890=

120591119898119886119909

120574119898119886119909=

120591119898119886119909

120574119898119886119909119894120596=

119866lowast

119894120596320

116






119866prime

120596322


imaginary portion


























details here

117







119866prime =12058212057812059621205740

1 + 12058221205962 119866primeprime =

1205781205961205740

1 + 12058221205962323










Log

mo

dul

us


119866primeprime

119866prime

(a)


Log

mo

dul

us


119866prime

119866primeprime

(b)



118

















unit of rad





r


119

119888 =1

119905119886119899120572∙ Ω = 119872 ∙ Ω 324






(Mezger 2020)

120591119888 = (3

2120587 ∙ 1198771198623) ∙ 119879 325



120578(119888) =120591119888

119888= (

3 ∙ 119879

2120587 ∙ 1198771198623) ∙

120572

Ω326









α

Rc

Cone

Plate

Tested sample

Ω



120









No pre-shear








Table 316 and 317











Conditions for OFS


121










Table 318



Geometry gap


Equilibrium time


Creep Step

Controlled variable


Duration 30 minutes

Recovery Step

Controlled variable


Number of points



3621 Theory




122







et al 2013)







(Danley 2002)








Temperature

programmer

(∆T=0)

Reference Sample

Individual heaters

pans (with lids)

Platinum

resistance

thermomete

rs (TR)


Platinum

resistance

thermomete

rs (TS)

Controller ∆

P


123

36212 Heat flux DSC




















Reference Sample


T

S

T

R

Heat flux

plate

Pans (with lids)

Insulating

heat sink

Thermocouples

Material 1


(Chromel wire)

∆

T


124



applied



119902 =119889119867

119889119905= 119862119901

119889119879

119889119905+ 119891(119879 119905) 327

















Sample Reference T0

RS Rr

TS TR

qS qR

CS CR

Tzero

thermocouple


125



119902119878 =1198790 minus 119879119878

119877119878minus 119862119878

119889119879119878

119889119905328

119902119877 =1198790 minus 119879119877

119877119877minus 119862119877

119889119879119877

119889119905329




119902 = 119902119878 minus 119902119877 = minus∆119879

119877+ ∆1198790 (

1

119877119878minus

1

119877119877) + (119862119877 minus 119862119878)

119889119879119878

119889119905minus 119862119877

119889∆119879

119889119905330

∆119879 = 119879119878 minus 119879119877 331

∆1198790 = 1198790 minus 119879119878 332


















126










3631 Theory












Incident Light




127









∆θ =122120582

119889333



II

(θ) II

(θ)

Sin

θ

Sin

θ

a b

Laser Light source


Diffracted image

Incident Light




128
























Droplet size

Vo

lum

e d

ensi

ty (

)


129


















D[32] =sum 119899119894119889119894

3119899119894=1

sum 1198991198941198891198942119899

119894=1

334





D[32] = 11988932 =119889119907

3

1198891199042 335

119889119907 = (6119881119901

120587)

13

336

119889119904 = radic119860119901

120587337



130















desired result

1 Optical unit

2 Wet dispersion

unit

3 Wet cell


software


131









around 5 to 15











injected sample






(Singh 2002)


119907119900119897119906119898119890 119900119891 119904119886119898119901119897119890=

119898

119907338






the instrument

132


364 Microscopy








3651 Theory







Dispersant (Water)

Stirrer Speed (rpm)


Ultrasound Mode


Analysis





10



10

133











F

dx

L

Surface


134


















119865 = 2γL cos 120579 = γ ∙ 4πR ∙ cos 120579 339

γ =119865

119871 cos 120579340


135
























Liquid

rin

g θ

L

F

Liquid

F

Lamella

ring


136
















3661 Theory




















137


















Ion

source


r

record

er

Ionisati

on

Accelerati

on

Deflectio

n

Detectio

n

electromagnet

vacuum

Vaporised sample


138




















ioniser

sample

+

-

-

+ -

MS

1

- fragment

-

- - MS

2

detector


fragmentation

mz separation

detection


139


Cream




preparation




















determination





computer

140










filling










water bath







Conditioning Step



Pre-Shear No




141




determination test








test


Conditioning Step



Pre-Shear No











test





142


water bath


Conditioning Step




60 Duration (min)

5


Controlled variable


Frequency (Hz) 1






















143






















01

1

10

100

1000

10000

100000

1000000

10 100 1000

Vis

cosi

ty

Pa

S

Shear Stress Pa


144




















1

10

100

1000

10000

01 1 10 100

GG

P

a

Osc Stress Pa

G

G


145



















100

1000

10000

100000

0 20 40 60 80 100 120 140

G

G

Pa

Time min

G

G


146





















Conditioning Step




50 Duration (min)

5




147


Conditioning Step




50 Duration (min)

5



10-150


150-10






Table 46


Conditioning Step




50 Duration (min)

5









148




measurement)


Conditioning Step




50 Duration (min)

5























149





















001

010

100

1000

10000

100000

1000000

10000000

100000000

10 100 1000

Vis

cosi

ty P

a∙S

shear stress Pa


150




































151





















(380E-04 5412)

0

40

80

120

160

0 100 200 300 400 500

Sh

ear S

tress

P

a

Shear Rate s⁻sup1

Ramp Up

Ramp Down


152
















EV




10

100

1000

10000

001 01 1 10 100 1000

G

G

P

a


G

G


stress of 4 Pa

153









procedure










Dispersant (Water)

Stirrer Speed (rpm)



133


089

Analysis



Mie




10


01-20


10

154




















112 08

518 72

272 0

0

2

4

6

8

001 01 1 10 100 1000 10000

volu

me

den

sity

droplet size um

E45 without sles

E45 cream+2SLES


SLES

155














distribution













as reference cell







156






(5) Mark the cycle

















157












158










standard E45 cream















159


























160









in Table 51









513 814E+04

2738 365E+05

7924 219E+04

2506 187E+05

01

1

10

100

1000

10000

100000

1000000

1 10 100 1000

Vis

cosi

ty

Pa

S

Shear Stress Pa

E45


mimic cream




161


Product





E45 cream 2738 3288times105 5130 lt0211


2506 1704times105 7924 0407
























162
















explanation

SLES wt CA (wt)

GM (wt)

0 2 4 6

6 6

6 2

2 6

2 2


163


Formulation_Ⅰ
















obtained















164





















165

































166



[2 6 2] [4 6 2] [6 6 2]









264E+05

139E+05

600E+04

0

10

20

30

40

50

10E+01

50E+04

10E+05

15E+05

20E+05

25E+05

30E+05

262 462 662

yie

ld s

tress

Pa

Vis

co

sit

y P

as



yield stress


167





















amphiphiles
















168






value




























169

5106

1273254

07371

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()

[SLESCAGM] of [262]

G

G

Critical strain

8992

591542

07301

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()


G

8292

998696

09001

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()

[SLESCAGM] of [662]

G

G

Critical strain

LVER

LVER

LVER

τy=24125

Critical strain

τy=33926



170


































171




































172













173

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ| P

as

G

G

P

a

Frequency Hz

[SLESCAGM] of [262]

G

G

|ƞ|

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ

| P

as

G

G

P

a

Frequency Hz


G

G

|ƞ|

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ| P

as

G

G

P

a

Frequency Hz

[SLESCAGM] of [662]

G

G

|ƞ|



174



















01

1

10

100

1000

10000

100000

1000000

000001 0001 01 10 1000

Dyn

am

ic v

isco

sit

y co

mp

lex v

isco

sit

y P

as






175


















500

5000

50000

001 01 1 10 100

G

G

P

a

Frequency Hz

G-cream [2 6 2] G-cream [2 6 2]

G-cream [4 6 2] G-cream [4 6 2]

G-cream [6 6 2] G-cream [6 6 2]



176





























177















properties





02

04

06

08

001 01 1 10 100

Dis

sip

ati

on

facto

r (

tan

δ)

Frequency Hz

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]



178

















0

1

2

3

4

5

6

7

8

0 500 1000 1500 2000 2500 3000 3500 4000

J 1

0⁻sup3

Pa⁻

sup1

Time s

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]




179














Com

pli

ance

Time

O

A

B

C

D


Primary creep

Secondary creep

Residual compliance

Retardant recovery


E

G0 G1 Gi η0

τ0 η1

1

ηi



180


Formulation_Ⅰ




















181


















(a) (b)

(c)


182


Formulation_Ⅰ
















-4

-2

0

2

4

20 25 30 35 40 45 50 55 60 65 70 75 80

Hea

t Fl

ow

(N

orm

aliz

ed

) Q(W

g)


cetyl alcohol



183







-03

-02

-01

0

01

02

03

20 25 30 35 40 45 50 55 60 65 70 75 80

Hea

t Fl

ow

(N

orm

aliz

ed) Q

(W

g)


white soft paraffin




184















more mobile






-025

-020

-015

30 40 50 60 70

Heat

Flo

w Q

(Wg

)


262

462

662



185











[2 5 2] [2 6 2] [2 7 2]





















186



[4 5 2] [4 6 2] [4 7 2]























different systems

187




























188


Different Processes










Heating Procedure





















189









(min)


[2 6 2] [4 6 2] [6 6 2]






0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm




190

















0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm




191











[2 6 2] [4 6 2] [6 6 2]








[2 6 2] [4 6 2] [6 6 2]






192


Heating Procedure


















0

3

6

9

12

01 1 10 100 1000

Vo

lum

e D

en

sit

y

Diameter μm

Cream [2 6 2]500rpm

700rpm

900rpm



193











1

2

3

4

5

6

7

8

9

10


D[3

2] μ

m

Mixing speed

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]


194





















A 200 20

B 200 5

C 300 10

D 200 10

E 0 10

195


Cooling Procedure

A B C D E

200rpm 20min

200rpm 5min

300rpm 10min

200rpm 10min

0rpm 10min

times105 η0






k -19923 -19405 -52341 -17865 -42169

01

1

10

100

1000

10000

100000

1000000

1 10 100 1000

Vis

cosi

ty

Pa

s

Shear stress Pa

200rpm20min

200rpm5min

300rpm10min

200rpm10min

0rpm10min



196




































197

100

1000

10000

100000

01 1 10 100

G

Pa

Frequency Hz

300rpm10min

200rpm10min

0rpm10min

100

1000

10000

100000

01 1 10 100

G

Pa

Frequency Hz

200rpm5min

200rpm10min

200rpm20min





198

















199












Oil

Media

SLs

Broth

SLs Cell pellet

Sedimentation

(a) (b)


200





















(a) (b)


201


















202










erucic acid (C22)











with C181

Diacylated acidic

SLs with C181

Diacylated acidic

SLs with C201


with C252

7333223

6873149


203













30

40

50

60

70

80

0 30 60 90 120 150 180 210 240 270 300 330

surfa

ce t

en

sion

(m

Nmiddotm

-1)



204














of biosurfactants

(a) (b)


205







MW 6704

MW 6564

MW 6964



206














structure of MELs

Possible fatty

acids chain

combinations

5352741 5343 MEL-D C81-80

6433460 6423 MEL-A C81-102

6573792 6564 MEL-BMEL-C C102-121C101-

122C81-142

6713578 6704 MEL-A C101-102C81-

122

6973735 6964 MEL-A C102-122

7133647 7124 MEL-BMEL-C C81-182C121-

142C121-

142C102-161

7313800 7304 MEL-A C101-140C120-

121C81-160

8956104 8946 MEL-A C183-183

9616177 9606 MEL-A C201-200

207


MELs











-025

-02

-015

-01

-005

0

005

01

015

02

-20 -10 0 10 20 30 40 50 60 70 80 90

Hea

t F

low

W

g

Temperature degC

ramp up

equilibrium

ramp down

equilibrium

ramp up

-025

-02

-015

-01

-005

0

005

01

015

02

-20 -10 0 10 20 30 40 50 60 70 80 90

Hea

t F

low

W

g

Temperature degC




208
















209



Formulation_Ⅲ






their performance










Configuration





configurations








210

















10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [2 6 2]

First Batch

Third Batch

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [4 6 2]

First Batch

Third Batch

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [6 6 2]

First Batch

Third Batch



211

















Mixed Paraffin oils


(wt) GM

(wt)

2 4 6

6 2


2 4 6


oils-water system

212


































213




















214














228E+03

175E+03

222E+02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa


Cream [4MELs 6 2]

Cream [6MELs 6 2]



215






















216

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()


G

G

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()


G

G

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()


G

G



217






























218

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ

| P

as

G

G

Pa

Frequency Hz


G

G

|n|

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ

| P

as

G

G

Pa

Frequency Hz


G

G

|n|

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ|

Pa

s

G

G

Pa

Frequency Hz


G

G

|n|



219






















10E+02

10E+03

001 01

G

G

Pa

Frequency Hz


G

G

10E+03

10E+04

10 100

G

G

Pa

Frequency Hz


G

G



220



et al 2018)



















221

10E+02

10E+03

10E+04

10E+05

001 01 1 10

G

G

P

a

Frequency Hz

Mixed Paraffin Oils




10E+02

10E+03

10E+04

001 01 1 10

G

G

P

a

Frequency Hz

Mixed Paraffin Oils






222




















0

005

01

015

02

025

03

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa

⁻sup1

Time s

Mixed Paraffin Oils

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

0

03

06

09

12

15

18

0 1000 2000 3000 4000

J

10

⁻sup2 P

a⁻sup1

Time s



223



















0

1

2

3

4

5

6

7

8

9

10

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa⁻sup1

Time s

Mixed Paraffin Oils

Cream [6MELs 6 2]

Cream [4MELs 6 2]

Cream [2MELs 6 2]



224

-04

-03

-02

-01

0

01

02

03

04

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

Wg

Temperature degC

Mixed Paraffin Oils

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

-04

-03

-02

-01

0

01

02

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

mW

mg

Temperature degC

Mixed Paraffin Oils

Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]



225
















Coconut Oil

SLES (wt) CA

(wt) GM

(wt)

2 4 6

6 2

2 4 6

SLES (wt)


226


















Coconut Oil


(wt) GM

(wt)

2 4 6

6 2


2 4 6



227









creep test









(wt) GM

(wt)

2 4 6

6 2


2 4 6


228






























229

205E+05

108E+05

546E+04

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

01 1 10 100 1000

vis

cosi

ty

Pas

Shear Stress Pa

Coconut Oils

Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]

276E+06

248E+05

130E+05

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

10E+07

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa


Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]





230



















181E+04167E+04

165E+04

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Coconut Oil

Cream [6SLs 6 2]

Cream [4SLs 6 2]

Cream [2SLs 6 2]



231



water system











stress





128E+05

271E+05

925E+05

100E-02

100E-01

100E+00

100E+01

100E+02

100E+03

100E+04

100E+05

100E+06

100E+07

01 1 10 100 1000

vis

cosi

ty

Pas

Shear Stress Pa


Cream [6SLs 6 2]

Cream [4SLs 6 2]

Cream [2SLs 6 2]



232














118E+05

171E+04

57E+03

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Coconut Oil

Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]



233



















639E+05

569E+05

214E+06

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

10E+07

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa


Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]



234





LVE range

00895

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

0001 001 01 1 10

G

G

Pa

strain()


G

G

0746510E-01

10E+00

10E+01

10E+02

10E+03

10E+04

0001 001 01 1 10 100

G

G

Pa

strain()


G

G





235











50E+01

50E+02

50E+03

50E+04

001 01 1 10 100

G

G

P

a

Frequency Hz

Coconut Oils






236

50E+01

50E+02

50E+03

50E+04

001 01 1 10 100

G

G

P

a

Frequency Hz





10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

G

G

P

a

Frequency Hz

Coconut Oil







237

50E+01

50E+02

50E+03

50E+04

001 01 1 10

G

G

P

a

Frequency Hz

Coconut Oil




10E+02

10E+03

10E+04

10E+05

10E+06

001 01 1 10 100

G

G

P

a

Frequency Hz









238



















50E+01

50E+02

50E+03

50E+04

50E+05

50E+06

001 01 1 10

G

G

P

a

Frequency Hz







239























4 wt involved










(Nguyen et al 2015)

240




water system

241

















et al 2016)

0

01

02

03

04

05

06

07

08

09

1

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa

⁻sup1

Time s

Coconut Oil

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

0

2

4

6

8

0 1000 2000 3000 4000

J

10

⁻sup2 P

a⁻sup1

Time s


water system

242

-03

-02

-01

0

01

02

03

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

mW

mg

Temperature degC


Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]



243












244
































245





































246




































247




































248



SLES solution





























249

















250




















251


















252
















253

















254


















255




















256

















257


















258




















259



















260

















261

















262


















263


















264


















265




















266


















267


















268


















269


















270



















271



















272



















273



















274




















275


















276




















277


















278


















279

















280












2


322 Chemicals 84








90

341 Chemicals 90

342 Recipes 90






Procedure 98


Procedure 99



361 Rheology 101



364 Microscopy 132



MS) 136








3






System 158







161



163


Formulation_Ⅰ 180



Formulation_Ⅱ 184




188


192










4






System 210










References 249

5

List of Figures




water surface 39







89
























profile 114






122



6


particles 126





size classes 128


unit 130





view (right) 135








145







stress of 4 Pa 152



154












300 Pa 164

7


































software) 183










8







193










100 Hz 197






spectrometry 202




fermentation 204



from 600 to 750 205













9





















water system 222























10










































water system 240



water system 241

11







12

List of Tables



















alcohols 92


system 94











100



2020 105






13


140




142






















specified 194




14

Abstract



































15

Declarations













copies made















16

Acknowledgements












17


11 Research System






















c Bulk water











18












products











ingredients Weight

concentration (wt)

function




lanolin 10





Sodium Hydroxide




Purified water

19




















13 State-of-the-Art
















20





































21





































22
















Lin et al 2016b)


















2020)

23





































24





































25





































26




































27




































28



(Lukic et al 2016)

















formulations

















29





































30

























their structure




cream performance




31









16 Nomenclature




Cetyl alcohol CA


Sophorolipids SLs


Biosurfactants BSs

32




rheology

21 Surfactants


















surf

ace

ten

sio

in


surfactant solutes



33


Shah 2013)
















et al 2016)







Hydrophilic head

(Polar)



34


in Table 21


Name and Structure

Stearalkonium

Chloride

Cetrimonium

Chloride

Dicetyldimonium

Chloride




















35











representatives








Carboxylates

(-COOM)

Sodium Stearate

C17H35-COO--Na+

Sulfonates

(-SO3M)


C18H29-SO3--Na+

Sulfate

esters

(-OSO3M)


C16H33-O-SO3--2Na+

36





et al 2017b)






























37


et al 2012)

















Name and Structure

Cetyl

alcohol

Glycerol

mono-

stearate

Sorbian

mono-

stearate

(Span 60)


(Tween 60)

38



























2020)

39





2131 Monomers














(Rehman et al 2017)



air

water

a) cationic

b) anionic

c) Non-ionic

d) Amphoteric



40











2132 Micelles
























41





























42




















Tem

pe

ratu

re H

igh


Critical

Micelle

Concentrati

on (CMC)


Molecular

soluble phase

Krafft

Point

So

lid

Are

a

Micelle Solution


Area

Middle Phase

(Hexagon

form)

Lamellar

Phase

Cubic

Phase

Tc boundary

Cloud Point

boundary

Liquid-liquid

phase Separation

Spheric

Micelle

s

Rodlike

Micelle

s


43
















44

22 Bio-surfactants




































45









2016)











Low mass BSs

Glycolipids



Trehalolipids

Lipopeptides and

lipoprotein


Polymyxin



High mass BSs




Wholecells




46




































47






































48



































49








2016)





















et al 2019)







50





































51




































52





































53



































54
















enhanced


55

























Acidic Sophorolipid


56

















a) Substrates



















57


et al 2019)

































58




































59





































60


















61






















O O

CH2

C

C

CH2

OH

OH

H

H OR1

CH3

CH3

R2

O


R2=H MEL-D R1=R2=H


62

































2020)

63





































64




































65
























Beck et al 2019)

23 Emulsion







2019)

66


































67
















(Wang et al 2018b)

∆119875119871 =4120574

11988922














68



































69















31186~32865 mN m-1 (Ibrahim et al 2015)





















70




































71


al 2016)




























(Krasinski 2013)

120578119888119900119886119897 = exp (minus119905119889

119905119888) 23



72















119889119898119894119899311 =

120574138119861046

00272120583119888120588119888084휀089

24


















73



































74







V =1198632(120588119878 minus 120588119874)119892

1812057825













Good emulsion


Creaming Breaking


75

24 Rheology

































76









ṙ =V

h26




Lange 1970)



calculation

Calculation

values of shear

rate

ṙ (s-1)


Velocity 2cms

1

Rubbing on

the skin



extending 24 cms

120



extending 10 cms

100



extending 10 cms

103



extending 10 cms

104





77




































78





































79















2002)






















80








Stern 2011)



























81





methods








-80 degC

312 Chemicals














2019)




82



al 2019)

















2019)















83















Equation 31

1198821 minus 11988210

119881times 100 31

















84


(Dolman et al 2017)














for further use

322 Chemicals







Hexane

Parameters Input




20 to 70



Wavelength of UV

Detector

207

85


































86















3311 Chemicals




formulation

3312 Recipes



Table 32



(wt)

Mass

(g)

Oil Phase (A)

White soft paraffin


Cetyl alcohol

145

126

12

58

504

48

Aqueous Phase (B)

Deionized water

609

2346


87





mixing


















water





3321 Chemicals





88

3322 Recipes



Table 33










England LTD)


(wt)

Mass

(g)

Oil Phase (A)

White soft paraffin


Cetyl alcohol

145

126

6

58

504

24

Aqueous Phase (B)

Deionized water

SLES

609

2346

6 24


NA

89


















water

Oil

phase

Aqueous

phase


90


Cream Formulation









341 Chemicals










Phases Components



Block

Emulsifying system



monostearate



342 Recipes




91











preservatives


surfactant system






Mimic Creams


Component (wt)

White soft paraffin

145 145 145 145


126 126 126 126

SLES 0 2 4 6 0 2 4 6 0 2 4 6 0 2 4 6

Cetyl Alcohol (CA)

6 6 2 2


(GM) 6 2 6 2


Residuals 5

92




fatty alcohols




















Mimic Creams

Ingredients F5 F6

Component (wt)



SLES 2 4

CA 5 6 7 5 6 7

GM 2 2


residuals 5

93



94








CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2








CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2








CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2


95










cold tap water















96










Ingredients


White Soft Paraffin


Cetyl Alcohol (CA)


Deionized Water


(SLES)

Water Tap

Water

Bath

D

H

T

Parameters Values

D (mm)

H (mm)

T (mm)

60

137

70

Clam

p

Clamp

Clam

p

Clamp

(b)

(a) (c)

(d)

Storage

Sink



97








cylinder was added



















temperature










98



39



Heating Procedure


















Component


(wt)


(wt)


(wt)



126 126 126

SLES 2 4 6

CA 6 6 6

GM 2 2 2

Residules

(not in the

formulation)

5 5 5


99


was set at 200 rpm

















procedure









Cream Sample

Mixing Procedure

Mixing Speed

(rpm)

Mixing Duration

(min)

A

500

3

B 5

C 10

D 15

E 20

100

















Cream Sample

Mixing Procedure

Mixing Speed

(rpm)

Mixing Duration

(min)

A 500

10 B 700

C 900

Cream


Mixing Speed

(rpm)

Mixing Duration

(min)

Stirring speed

(rpm)

Cooling Duration

(min)

A

500

10

200 10

B 0 10

C 300 10

D 200 5

E 200 20

101


analysis

361 Rheology


















Equation 32

120591 =119865

11986032




120574 =∆119909

∆11991033


two plates



velocity u

102

=119889120574

119889119905=

119889

119889119905(

119889119909

119889119910) =

119889

119889119910(

119889119909

119889119905) =

119889119906

11988911991034




35 and 36

120591 = minus120583 (119889119906

119889119910) 35

120583 =120591

36








() (Mezger 2020)

120591 = minus120578 (119889119906

119889119910) 37


103










Pure viscous

fluid

Time independent

Newtonian fluid


Non-Newtonian fluid



Time dependent

Thixotropic fluid

Rheopectic fluid



104























105


starts to alter






in Figure 35



Bingham Model






above yield point

120636119942119943119943 = 120636119942119943119943infin +120649119962

Where





Model

120636119942119943119943 = 119948(119931) ∙ 119951minus120783

Where

119897119900119892 or 119897119900119892120591

119897119900119892

120578

1st Newtonian

Plateau


1205780

120578infin


Ellis model

Sisko model


106



119949119952119944120636 minus 119949119952119944120649 curve


plateau





power law model






above yield point

120649 = 120649119962 + 119948(119931) ∙ 119951

Where











the transient area



120578119890119891119891() minus 120578infin

1205780 minus 120578infin= (1 + |120582 ∙ |119886)

119899minus1119886


∙ (1 + |120582 ∙ |119886)119899minus1

119886

Where







as follow

120636119942119943119943() =120636120782

(120783 + |120640 ∙ |119938)119951minus120783

119938

Cross Model




120578119890119891119891() minus 120578infin

1205780 minus 120578infin=

1

1 + (119870 ∙ )1minus119899

Where


107


119949119952119944 curve




120636119942119943119943() =120636120782

120783 + (120636120782 ∙

120649lowast )120783minus119951


119870frasl

Ellis Model






region

120636119942119943119943() =120636120782

120783 + (120649

120649120783120784frasl

)

120630minus120783

Where



120578119890119891119891 decreased to 120578119890119891119891

2frasl


Sisko Model






region

120636119942119943119943() = 119922 ∙ 119951minus120783 + 120636infin

Where













108










Shea

r st

ress

120591

Shear rate

Thixotropic fluid

Rheopectic fluid

Fτ

Fτ

Δx

Δx



109

120590119866 = E ∙ ε119866 38


120591120578 = 120578 ∙119889120574120578

119889119905= 120578 ∙ 120578 39






119864frasl




=1205910










dγ119905119900119905119886119897

dt=

1

119864∙

dτ119905119900119905119886119897

dt+

120591119905119900119905119886119897

120578310



τ

t t0=0 t1

τ

0

a ε

t t0=0 t1

1205980 1205980 =

1205910119864frasl

b γ

t t0=0 t1

γ

0

1205740 =1205910

120578(1199051 minus 1199050)

c


110

















ε

t t0=0 t1

휀0

b

휀0

τ

t t0=0 t1

τ0

a

휀1

휀1

η η

F F

η

E

∆119909120578

∆119909119864 F

t=T t=T t=T+ΔT

E E 120591119866 = E ∙ ε119866

120591120578 = 120578 ∙119889120574120578

119889119905



111

119889γ119905119900119905119886119897

119889119905=

120591119905119900119905119886119897

120578minus

E

120578∙ γ119905119900119905119886119897 311













is 120649120782





120574120578

120591120578 = 120578 ∙119889120574120578

119889119905

γ119866

120591119866 = G ∙ γ119866

F 120591119905119900119905119886119897


112

Burgers Model
















120574

t t0 t1

b τ

t t0=0 t1

τ0

a

F τtotal

E3

Ⅲ

η2

Ⅱ E1

Ⅰ

η4

Ⅳ

120598

t

t0 t1

E1_R

E3 η2_C

η

4

E1_C

E3

η2_R

Creep

strain

Permanent

strain

b) a)



113






119869(119905) =120574(119905)

120591312




log t t0

log c

reep

com

pli

ance

J

Elastic material

Viscous material


114










313 (Mezger 2006)

120574 = 120574119898119886119909 sin 120596119905 = 120574119898119886119909119890119894120596119905 313





120591 = 120591119898119886119909 sin(120596119905 + 120575) = 120591119898119886119909119890119894(120596119905+120575) 314


amplitude



0

deg

90

deg

180

deg

270

deg

360

deg

0deg360

deg

90

deg

180deg

27

0deg

90

deg 27

0deg


115





120575 lt 90deg) (Lade et al 2019)





119866lowast =119888119900119898119901119897119890119909 119904119905119903119890119904119904 119886119898119901119897119894119905119906119889119890

119888119900119898119901119897119890119909 119904119905119903119886119894119899 119886119898119901119897119894119905119906119889119890=

120591119898119886119909120574119898119886119909

frasl 315


the shear strain





these terms

119866prime = 119866lowast cos 120575 =120591119898119886119909

120574119898119886119909cos 120575 316


120574119898119886119909sin 120575 317



119866prime319






120578lowast =119888119900119898119901119897119890119909 119904119905119903119890119904119904 119886119898119901119897119894119905119906119889119890

119888119900119898119901119897119890119909 119904119905119903119886119894119899 119903119886119905119890 119886119898119901119897119894119905119906119889119890=

120591119898119886119909

120574119898119886119909=

120591119898119886119909

120574119898119886119909119894120596=

119866lowast

119894120596320

116






119866prime

120596322


imaginary portion


























details here

117







119866prime =12058212057812059621205740

1 + 12058221205962 119866primeprime =

1205781205961205740

1 + 12058221205962323










Log

mo

dul

us


119866primeprime

119866prime

(a)


Log

mo

dul

us


119866prime

119866primeprime

(b)



118

















unit of rad





r


119

119888 =1

119905119886119899120572∙ Ω = 119872 ∙ Ω 324






(Mezger 2020)

120591119888 = (3

2120587 ∙ 1198771198623) ∙ 119879 325



120578(119888) =120591119888

119888= (

3 ∙ 119879

2120587 ∙ 1198771198623) ∙

120572

Ω326









α

Rc

Cone

Plate

Tested sample

Ω



120









No pre-shear








Table 316 and 317











Conditions for OFS


121










Table 318



Geometry gap


Equilibrium time


Creep Step

Controlled variable


Duration 30 minutes

Recovery Step

Controlled variable


Number of points



3621 Theory




122







et al 2013)







(Danley 2002)








Temperature

programmer

(∆T=0)

Reference Sample

Individual heaters

pans (with lids)

Platinum

resistance

thermomete

rs (TR)


Platinum

resistance

thermomete

rs (TS)

Controller ∆

P


123

36212 Heat flux DSC




















Reference Sample


T

S

T

R

Heat flux

plate

Pans (with lids)

Insulating

heat sink

Thermocouples

Material 1


(Chromel wire)

∆

T


124



applied



119902 =119889119867

119889119905= 119862119901

119889119879

119889119905+ 119891(119879 119905) 327

















Sample Reference T0

RS Rr

TS TR

qS qR

CS CR

Tzero

thermocouple


125



119902119878 =1198790 minus 119879119878

119877119878minus 119862119878

119889119879119878

119889119905328

119902119877 =1198790 minus 119879119877

119877119877minus 119862119877

119889119879119877

119889119905329




119902 = 119902119878 minus 119902119877 = minus∆119879

119877+ ∆1198790 (

1

119877119878minus

1

119877119877) + (119862119877 minus 119862119878)

119889119879119878

119889119905minus 119862119877

119889∆119879

119889119905330

∆119879 = 119879119878 minus 119879119877 331

∆1198790 = 1198790 minus 119879119878 332


















126










3631 Theory












Incident Light




127









∆θ =122120582

119889333



II

(θ) II

(θ)

Sin

θ

Sin

θ

a b

Laser Light source


Diffracted image

Incident Light




128
























Droplet size

Vo

lum

e d

ensi

ty (

)


129


















D[32] =sum 119899119894119889119894

3119899119894=1

sum 1198991198941198891198942119899

119894=1

334





D[32] = 11988932 =119889119907

3

1198891199042 335

119889119907 = (6119881119901

120587)

13

336

119889119904 = radic119860119901

120587337



130















desired result

1 Optical unit

2 Wet dispersion

unit

3 Wet cell


software


131









around 5 to 15











injected sample






(Singh 2002)


119907119900119897119906119898119890 119900119891 119904119886119898119901119897119890=

119898

119907338






the instrument

132


364 Microscopy








3651 Theory







Dispersant (Water)

Stirrer Speed (rpm)


Ultrasound Mode


Analysis





10



10

133











F

dx

L

Surface


134


















119865 = 2γL cos 120579 = γ ∙ 4πR ∙ cos 120579 339

γ =119865

119871 cos 120579340


135
























Liquid

rin

g θ

L

F

Liquid

F

Lamella

ring


136
















3661 Theory




















137


















Ion

source


r

record

er

Ionisati

on

Accelerati

on

Deflectio

n

Detectio

n

electromagnet

vacuum

Vaporised sample


138




















ioniser

sample

+

-

-

+ -

MS

1

- fragment

-

- - MS

2

detector


fragmentation

mz separation

detection


139


Cream




preparation




















determination





computer

140










filling










water bath







Conditioning Step



Pre-Shear No




141




determination test








test


Conditioning Step



Pre-Shear No











test





142


water bath


Conditioning Step




60 Duration (min)

5


Controlled variable


Frequency (Hz) 1






















143






















01

1

10

100

1000

10000

100000

1000000

10 100 1000

Vis

cosi

ty

Pa

S

Shear Stress Pa


144




















1

10

100

1000

10000

01 1 10 100

GG

P

a

Osc Stress Pa

G

G


145



















100

1000

10000

100000

0 20 40 60 80 100 120 140

G

G

Pa

Time min

G

G


146





















Conditioning Step




50 Duration (min)

5




147


Conditioning Step




50 Duration (min)

5



10-150


150-10






Table 46


Conditioning Step




50 Duration (min)

5









148




measurement)


Conditioning Step




50 Duration (min)

5























149





















001

010

100

1000

10000

100000

1000000

10000000

100000000

10 100 1000

Vis

cosi

ty P

a∙S

shear stress Pa


150




































151





















(380E-04 5412)

0

40

80

120

160

0 100 200 300 400 500

Sh

ear S

tress

P

a

Shear Rate s⁻sup1

Ramp Up

Ramp Down


152
















EV




10

100

1000

10000

001 01 1 10 100 1000

G

G

P

a


G

G


stress of 4 Pa

153









procedure










Dispersant (Water)

Stirrer Speed (rpm)



133


089

Analysis



Mie




10


01-20


10

154




















112 08

518 72

272 0

0

2

4

6

8

001 01 1 10 100 1000 10000

volu

me

den

sity

droplet size um

E45 without sles

E45 cream+2SLES


SLES

155














distribution













as reference cell







156






(5) Mark the cycle

















157












158










standard E45 cream















159


























160









in Table 51









513 814E+04

2738 365E+05

7924 219E+04

2506 187E+05

01

1

10

100

1000

10000

100000

1000000

1 10 100 1000

Vis

cosi

ty

Pa

S

Shear Stress Pa

E45


mimic cream




161


Product





E45 cream 2738 3288times105 5130 lt0211


2506 1704times105 7924 0407
























162
















explanation

SLES wt CA (wt)

GM (wt)

0 2 4 6

6 6

6 2

2 6

2 2


163


Formulation_Ⅰ
















obtained















164





















165

































166



[2 6 2] [4 6 2] [6 6 2]









264E+05

139E+05

600E+04

0

10

20

30

40

50

10E+01

50E+04

10E+05

15E+05

20E+05

25E+05

30E+05

262 462 662

yie

ld s

tress

Pa

Vis

co

sit

y P

as



yield stress


167





















amphiphiles
















168






value




























169

5106

1273254

07371

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()

[SLESCAGM] of [262]

G

G

Critical strain

8992

591542

07301

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()


G

8292

998696

09001

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()

[SLESCAGM] of [662]

G

G

Critical strain

LVER

LVER

LVER

τy=24125

Critical strain

τy=33926



170


































171




































172













173

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ| P

as

G

G

P

a

Frequency Hz

[SLESCAGM] of [262]

G

G

|ƞ|

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ

| P

as

G

G

P

a

Frequency Hz


G

G

|ƞ|

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ| P

as

G

G

P

a

Frequency Hz

[SLESCAGM] of [662]

G

G

|ƞ|



174



















01

1

10

100

1000

10000

100000

1000000

000001 0001 01 10 1000

Dyn

am

ic v

isco

sit

y co

mp

lex v

isco

sit

y P

as






175


















500

5000

50000

001 01 1 10 100

G

G

P

a

Frequency Hz

G-cream [2 6 2] G-cream [2 6 2]

G-cream [4 6 2] G-cream [4 6 2]

G-cream [6 6 2] G-cream [6 6 2]



176





























177















properties





02

04

06

08

001 01 1 10 100

Dis

sip

ati

on

facto

r (

tan

δ)

Frequency Hz

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]



178

















0

1

2

3

4

5

6

7

8

0 500 1000 1500 2000 2500 3000 3500 4000

J 1

0⁻sup3

Pa⁻

sup1

Time s

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]




179














Com

pli

ance

Time

O

A

B

C

D


Primary creep

Secondary creep

Residual compliance

Retardant recovery


E

G0 G1 Gi η0

τ0 η1

1

ηi



180


Formulation_Ⅰ




















181


















(a) (b)

(c)


182


Formulation_Ⅰ
















-4

-2

0

2

4

20 25 30 35 40 45 50 55 60 65 70 75 80

Hea

t Fl

ow

(N

orm

aliz

ed

) Q(W

g)


cetyl alcohol



183







-03

-02

-01

0

01

02

03

20 25 30 35 40 45 50 55 60 65 70 75 80

Hea

t Fl

ow

(N

orm

aliz

ed) Q

(W

g)


white soft paraffin




184















more mobile






-025

-020

-015

30 40 50 60 70

Heat

Flo

w Q

(Wg

)


262

462

662



185











[2 5 2] [2 6 2] [2 7 2]





















186



[4 5 2] [4 6 2] [4 7 2]























different systems

187




























188


Different Processes










Heating Procedure





















189









(min)


[2 6 2] [4 6 2] [6 6 2]






0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm




190

















0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm




191











[2 6 2] [4 6 2] [6 6 2]








[2 6 2] [4 6 2] [6 6 2]






192


Heating Procedure


















0

3

6

9

12

01 1 10 100 1000

Vo

lum

e D

en

sit

y

Diameter μm

Cream [2 6 2]500rpm

700rpm

900rpm



193











1

2

3

4

5

6

7

8

9

10


D[3

2] μ

m

Mixing speed

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]


194





















A 200 20

B 200 5

C 300 10

D 200 10

E 0 10

195


Cooling Procedure

A B C D E

200rpm 20min

200rpm 5min

300rpm 10min

200rpm 10min

0rpm 10min

times105 η0






k -19923 -19405 -52341 -17865 -42169

01

1

10

100

1000

10000

100000

1000000

1 10 100 1000

Vis

cosi

ty

Pa

s

Shear stress Pa

200rpm20min

200rpm5min

300rpm10min

200rpm10min

0rpm10min



196




































197

100

1000

10000

100000

01 1 10 100

G

Pa

Frequency Hz

300rpm10min

200rpm10min

0rpm10min

100

1000

10000

100000

01 1 10 100

G

Pa

Frequency Hz

200rpm5min

200rpm10min

200rpm20min





198

















199












Oil

Media

SLs

Broth

SLs Cell pellet

Sedimentation

(a) (b)


200





















(a) (b)


201


















202










erucic acid (C22)











with C181

Diacylated acidic

SLs with C181

Diacylated acidic

SLs with C201


with C252

7333223

6873149


203













30

40

50

60

70

80

0 30 60 90 120 150 180 210 240 270 300 330

surfa

ce t

en

sion

(m

Nmiddotm

-1)



204














of biosurfactants

(a) (b)


205







MW 6704

MW 6564

MW 6964



206














structure of MELs

Possible fatty

acids chain

combinations

5352741 5343 MEL-D C81-80

6433460 6423 MEL-A C81-102

6573792 6564 MEL-BMEL-C C102-121C101-

122C81-142

6713578 6704 MEL-A C101-102C81-

122

6973735 6964 MEL-A C102-122

7133647 7124 MEL-BMEL-C C81-182C121-

142C121-

142C102-161

7313800 7304 MEL-A C101-140C120-

121C81-160

8956104 8946 MEL-A C183-183

9616177 9606 MEL-A C201-200

207


MELs











-025

-02

-015

-01

-005

0

005

01

015

02

-20 -10 0 10 20 30 40 50 60 70 80 90

Hea

t F

low

W

g

Temperature degC

ramp up

equilibrium

ramp down

equilibrium

ramp up

-025

-02

-015

-01

-005

0

005

01

015

02

-20 -10 0 10 20 30 40 50 60 70 80 90

Hea

t F

low

W

g

Temperature degC




208
















209



Formulation_Ⅲ






their performance










Configuration





configurations








210

















10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [2 6 2]

First Batch

Third Batch

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [4 6 2]

First Batch

Third Batch

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [6 6 2]

First Batch

Third Batch



211

















Mixed Paraffin oils


(wt) GM

(wt)

2 4 6

6 2


2 4 6


oils-water system

212


































213




















214














228E+03

175E+03

222E+02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa


Cream [4MELs 6 2]

Cream [6MELs 6 2]



215






















216

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()


G

G

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()


G

G

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()


G

G



217






























218

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ

| P

as

G

G

Pa

Frequency Hz


G

G

|n|

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ

| P

as

G

G

Pa

Frequency Hz


G

G

|n|

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ|

Pa

s

G

G

Pa

Frequency Hz


G

G

|n|



219






















10E+02

10E+03

001 01

G

G

Pa

Frequency Hz


G

G

10E+03

10E+04

10 100

G

G

Pa

Frequency Hz


G

G



220



et al 2018)



















221

10E+02

10E+03

10E+04

10E+05

001 01 1 10

G

G

P

a

Frequency Hz

Mixed Paraffin Oils




10E+02

10E+03

10E+04

001 01 1 10

G

G

P

a

Frequency Hz

Mixed Paraffin Oils






222




















0

005

01

015

02

025

03

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa

⁻sup1

Time s

Mixed Paraffin Oils

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

0

03

06

09

12

15

18

0 1000 2000 3000 4000

J

10

⁻sup2 P

a⁻sup1

Time s



223



















0

1

2

3

4

5

6

7

8

9

10

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa⁻sup1

Time s

Mixed Paraffin Oils

Cream [6MELs 6 2]

Cream [4MELs 6 2]

Cream [2MELs 6 2]



224

-04

-03

-02

-01

0

01

02

03

04

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

Wg

Temperature degC

Mixed Paraffin Oils

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

-04

-03

-02

-01

0

01

02

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

mW

mg

Temperature degC

Mixed Paraffin Oils

Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]



225
















Coconut Oil

SLES (wt) CA

(wt) GM

(wt)

2 4 6

6 2

2 4 6

SLES (wt)


226


















Coconut Oil


(wt) GM

(wt)

2 4 6

6 2


2 4 6



227









creep test









(wt) GM

(wt)

2 4 6

6 2


2 4 6


228






























229

205E+05

108E+05

546E+04

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

01 1 10 100 1000

vis

cosi

ty

Pas

Shear Stress Pa

Coconut Oils

Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]

276E+06

248E+05

130E+05

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

10E+07

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa


Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]





230



















181E+04167E+04

165E+04

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Coconut Oil

Cream [6SLs 6 2]

Cream [4SLs 6 2]

Cream [2SLs 6 2]



231



water system











stress





128E+05

271E+05

925E+05

100E-02

100E-01

100E+00

100E+01

100E+02

100E+03

100E+04

100E+05

100E+06

100E+07

01 1 10 100 1000

vis

cosi

ty

Pas

Shear Stress Pa


Cream [6SLs 6 2]

Cream [4SLs 6 2]

Cream [2SLs 6 2]



232














118E+05

171E+04

57E+03

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Coconut Oil

Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]



233



















639E+05

569E+05

214E+06

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

10E+07

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa


Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]



234





LVE range

00895

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

0001 001 01 1 10

G

G

Pa

strain()


G

G

0746510E-01

10E+00

10E+01

10E+02

10E+03

10E+04

0001 001 01 1 10 100

G

G

Pa

strain()


G

G





235











50E+01

50E+02

50E+03

50E+04

001 01 1 10 100

G

G

P

a

Frequency Hz

Coconut Oils






236

50E+01

50E+02

50E+03

50E+04

001 01 1 10 100

G

G

P

a

Frequency Hz





10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

G

G

P

a

Frequency Hz

Coconut Oil







237

50E+01

50E+02

50E+03

50E+04

001 01 1 10

G

G

P

a

Frequency Hz

Coconut Oil




10E+02

10E+03

10E+04

10E+05

10E+06

001 01 1 10 100

G

G

P

a

Frequency Hz









238



















50E+01

50E+02

50E+03

50E+04

50E+05

50E+06

001 01 1 10

G

G

P

a

Frequency Hz







239























4 wt involved










(Nguyen et al 2015)

240




water system

241

















et al 2016)

0

01

02

03

04

05

06

07

08

09

1

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa

⁻sup1

Time s

Coconut Oil

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

0

2

4

6

8

0 1000 2000 3000 4000

J

10

⁻sup2 P

a⁻sup1

Time s


water system

242

-03

-02

-01

0

01

02

03

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

mW

mg

Temperature degC


Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]



243












244
































245





































246




































247




































248



SLES solution





























249

















250




















251


















252
















253

















254


















255




















256

















257


















258




















259



















260

















261

















262


















263


















264


















265




















266


















267


















268


















269


















270



















271



















272



















273



















274




















275


















276




















277


















278


















279

















280












3






System 158







161



163


Formulation_Ⅰ 180



Formulation_Ⅱ 184




188


192










4






System 210










References 249

5

List of Figures




water surface 39







89
























profile 114






122



6


particles 126





size classes 128


unit 130





view (right) 135








145







stress of 4 Pa 152



154












300 Pa 164

7


































software) 183










8







193










100 Hz 197






spectrometry 202




fermentation 204



from 600 to 750 205













9





















water system 222























10










































water system 240



water system 241

11







12

List of Tables



















alcohols 92


system 94











100



2020 105






13


140




142






















specified 194




14

Abstract



































15

Declarations













copies made















16

Acknowledgements












17


11 Research System






















c Bulk water











18












products











ingredients Weight

concentration (wt)

function




lanolin 10





Sodium Hydroxide




Purified water

19




















13 State-of-the-Art
















20





































21





































22
















Lin et al 2016b)


















2020)

23





































24





































25





































26




































27




































28



(Lukic et al 2016)

















formulations

















29





































30

























their structure




cream performance




31









16 Nomenclature




Cetyl alcohol CA


Sophorolipids SLs


Biosurfactants BSs

32




rheology

21 Surfactants


















surf

ace

ten

sio

in


surfactant solutes



33


Shah 2013)
















et al 2016)







Hydrophilic head

(Polar)



34


in Table 21


Name and Structure

Stearalkonium

Chloride

Cetrimonium

Chloride

Dicetyldimonium

Chloride




















35











representatives








Carboxylates

(-COOM)

Sodium Stearate

C17H35-COO--Na+

Sulfonates

(-SO3M)


C18H29-SO3--Na+

Sulfate

esters

(-OSO3M)


C16H33-O-SO3--2Na+

36





et al 2017b)






























37


et al 2012)

















Name and Structure

Cetyl

alcohol

Glycerol

mono-

stearate

Sorbian

mono-

stearate

(Span 60)


(Tween 60)

38



























2020)

39





2131 Monomers














(Rehman et al 2017)



air

water

a) cationic

b) anionic

c) Non-ionic

d) Amphoteric



40











2132 Micelles
























41





























42




















Tem

pe

ratu

re H

igh


Critical

Micelle

Concentrati

on (CMC)


Molecular

soluble phase

Krafft

Point

So

lid

Are

a

Micelle Solution


Area

Middle Phase

(Hexagon

form)

Lamellar

Phase

Cubic

Phase

Tc boundary

Cloud Point

boundary

Liquid-liquid

phase Separation

Spheric

Micelle

s

Rodlike

Micelle

s


43
















44

22 Bio-surfactants




































45









2016)











Low mass BSs

Glycolipids



Trehalolipids

Lipopeptides and

lipoprotein


Polymyxin



High mass BSs




Wholecells




46




































47






































48



































49








2016)





















et al 2019)







50





































51




































52





































53



































54
















enhanced


55

























Acidic Sophorolipid


56

















a) Substrates



















57


et al 2019)

































58




































59





































60


















61






















O O

CH2

C

C

CH2

OH

OH

H

H OR1

CH3

CH3

R2

O


R2=H MEL-D R1=R2=H


62

































2020)

63





































64




































65
























Beck et al 2019)

23 Emulsion







2019)

66


































67
















(Wang et al 2018b)

∆119875119871 =4120574

11988922














68



































69















31186~32865 mN m-1 (Ibrahim et al 2015)





















70




































71


al 2016)




























(Krasinski 2013)

120578119888119900119886119897 = exp (minus119905119889

119905119888) 23



72















119889119898119894119899311 =

120574138119861046

00272120583119888120588119888084휀089

24


















73



































74







V =1198632(120588119878 minus 120588119874)119892

1812057825













Good emulsion


Creaming Breaking


75

24 Rheology

































76









ṙ =V

h26




Lange 1970)



calculation

Calculation

values of shear

rate

ṙ (s-1)


Velocity 2cms

1

Rubbing on

the skin



extending 24 cms

120



extending 10 cms

100



extending 10 cms

103



extending 10 cms

104





77




































78





































79















2002)






















80








Stern 2011)



























81





methods








-80 degC

312 Chemicals














2019)




82



al 2019)

















2019)















83















Equation 31

1198821 minus 11988210

119881times 100 31

















84


(Dolman et al 2017)














for further use

322 Chemicals







Hexane

Parameters Input




20 to 70



Wavelength of UV

Detector

207

85


































86















3311 Chemicals




formulation

3312 Recipes



Table 32



(wt)

Mass

(g)

Oil Phase (A)

White soft paraffin


Cetyl alcohol

145

126

12

58

504

48

Aqueous Phase (B)

Deionized water

609

2346


87





mixing


















water





3321 Chemicals





88

3322 Recipes



Table 33










England LTD)


(wt)

Mass

(g)

Oil Phase (A)

White soft paraffin


Cetyl alcohol

145

126

6

58

504

24

Aqueous Phase (B)

Deionized water

SLES

609

2346

6 24


NA

89


















water

Oil

phase

Aqueous

phase


90


Cream Formulation









341 Chemicals










Phases Components



Block

Emulsifying system



monostearate



342 Recipes




91











preservatives


surfactant system






Mimic Creams


Component (wt)

White soft paraffin

145 145 145 145


126 126 126 126

SLES 0 2 4 6 0 2 4 6 0 2 4 6 0 2 4 6

Cetyl Alcohol (CA)

6 6 2 2


(GM) 6 2 6 2


Residuals 5

92




fatty alcohols




















Mimic Creams

Ingredients F5 F6

Component (wt)



SLES 2 4

CA 5 6 7 5 6 7

GM 2 2


residuals 5

93



94








CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2








CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2








CA 6 6 6 CA 6 6 6 CA 6 6 6

GM 2 2 2 GM 2 2 2 GM 2 2 2


95










cold tap water















96










Ingredients


White Soft Paraffin


Cetyl Alcohol (CA)


Deionized Water


(SLES)

Water Tap

Water

Bath

D

H

T

Parameters Values

D (mm)

H (mm)

T (mm)

60

137

70

Clam

p

Clamp

Clam

p

Clamp

(b)

(a) (c)

(d)

Storage

Sink



97








cylinder was added



















temperature










98



39



Heating Procedure


















Component


(wt)


(wt)


(wt)



126 126 126

SLES 2 4 6

CA 6 6 6

GM 2 2 2

Residules

(not in the

formulation)

5 5 5


99


was set at 200 rpm

















procedure









Cream Sample

Mixing Procedure

Mixing Speed

(rpm)

Mixing Duration

(min)

A

500

3

B 5

C 10

D 15

E 20

100

















Cream Sample

Mixing Procedure

Mixing Speed

(rpm)

Mixing Duration

(min)

A 500

10 B 700

C 900

Cream


Mixing Speed

(rpm)

Mixing Duration

(min)

Stirring speed

(rpm)

Cooling Duration

(min)

A

500

10

200 10

B 0 10

C 300 10

D 200 5

E 200 20

101


analysis

361 Rheology


















Equation 32

120591 =119865

11986032




120574 =∆119909

∆11991033


two plates



velocity u

102

=119889120574

119889119905=

119889

119889119905(

119889119909

119889119910) =

119889

119889119910(

119889119909

119889119905) =

119889119906

11988911991034




35 and 36

120591 = minus120583 (119889119906

119889119910) 35

120583 =120591

36








() (Mezger 2020)

120591 = minus120578 (119889119906

119889119910) 37


103










Pure viscous

fluid

Time independent

Newtonian fluid


Non-Newtonian fluid



Time dependent

Thixotropic fluid

Rheopectic fluid



104























105


starts to alter






in Figure 35



Bingham Model






above yield point

120636119942119943119943 = 120636119942119943119943infin +120649119962

Where





Model

120636119942119943119943 = 119948(119931) ∙ 119951minus120783

Where

119897119900119892 or 119897119900119892120591

119897119900119892

120578

1st Newtonian

Plateau


1205780

120578infin


Ellis model

Sisko model


106



119949119952119944120636 minus 119949119952119944120649 curve


plateau





power law model






above yield point

120649 = 120649119962 + 119948(119931) ∙ 119951

Where











the transient area



120578119890119891119891() minus 120578infin

1205780 minus 120578infin= (1 + |120582 ∙ |119886)

119899minus1119886


∙ (1 + |120582 ∙ |119886)119899minus1

119886

Where







as follow

120636119942119943119943() =120636120782

(120783 + |120640 ∙ |119938)119951minus120783

119938

Cross Model




120578119890119891119891() minus 120578infin

1205780 minus 120578infin=

1

1 + (119870 ∙ )1minus119899

Where


107


119949119952119944 curve




120636119942119943119943() =120636120782

120783 + (120636120782 ∙

120649lowast )120783minus119951


119870frasl

Ellis Model






region

120636119942119943119943() =120636120782

120783 + (120649

120649120783120784frasl

)

120630minus120783

Where



120578119890119891119891 decreased to 120578119890119891119891

2frasl


Sisko Model






region

120636119942119943119943() = 119922 ∙ 119951minus120783 + 120636infin

Where













108










Shea

r st

ress

120591

Shear rate

Thixotropic fluid

Rheopectic fluid

Fτ

Fτ

Δx

Δx



109

120590119866 = E ∙ ε119866 38


120591120578 = 120578 ∙119889120574120578

119889119905= 120578 ∙ 120578 39






119864frasl




=1205910










dγ119905119900119905119886119897

dt=

1

119864∙

dτ119905119900119905119886119897

dt+

120591119905119900119905119886119897

120578310



τ

t t0=0 t1

τ

0

a ε

t t0=0 t1

1205980 1205980 =

1205910119864frasl

b γ

t t0=0 t1

γ

0

1205740 =1205910

120578(1199051 minus 1199050)

c


110

















ε

t t0=0 t1

휀0

b

휀0

τ

t t0=0 t1

τ0

a

휀1

휀1

η η

F F

η

E

∆119909120578

∆119909119864 F

t=T t=T t=T+ΔT

E E 120591119866 = E ∙ ε119866

120591120578 = 120578 ∙119889120574120578

119889119905



111

119889γ119905119900119905119886119897

119889119905=

120591119905119900119905119886119897

120578minus

E

120578∙ γ119905119900119905119886119897 311













is 120649120782





120574120578

120591120578 = 120578 ∙119889120574120578

119889119905

γ119866

120591119866 = G ∙ γ119866

F 120591119905119900119905119886119897


112

Burgers Model
















120574

t t0 t1

b τ

t t0=0 t1

τ0

a

F τtotal

E3

Ⅲ

η2

Ⅱ E1

Ⅰ

η4

Ⅳ

120598

t

t0 t1

E1_R

E3 η2_C

η

4

E1_C

E3

η2_R

Creep

strain

Permanent

strain

b) a)



113






119869(119905) =120574(119905)

120591312




log t t0

log c

reep

com

pli

ance

J

Elastic material

Viscous material


114










313 (Mezger 2006)

120574 = 120574119898119886119909 sin 120596119905 = 120574119898119886119909119890119894120596119905 313





120591 = 120591119898119886119909 sin(120596119905 + 120575) = 120591119898119886119909119890119894(120596119905+120575) 314


amplitude



0

deg

90

deg

180

deg

270

deg

360

deg

0deg360

deg

90

deg

180deg

27

0deg

90

deg 27

0deg


115





120575 lt 90deg) (Lade et al 2019)





119866lowast =119888119900119898119901119897119890119909 119904119905119903119890119904119904 119886119898119901119897119894119905119906119889119890

119888119900119898119901119897119890119909 119904119905119903119886119894119899 119886119898119901119897119894119905119906119889119890=

120591119898119886119909120574119898119886119909

frasl 315


the shear strain





these terms

119866prime = 119866lowast cos 120575 =120591119898119886119909

120574119898119886119909cos 120575 316


120574119898119886119909sin 120575 317



119866prime319






120578lowast =119888119900119898119901119897119890119909 119904119905119903119890119904119904 119886119898119901119897119894119905119906119889119890

119888119900119898119901119897119890119909 119904119905119903119886119894119899 119903119886119905119890 119886119898119901119897119894119905119906119889119890=

120591119898119886119909

120574119898119886119909=

120591119898119886119909

120574119898119886119909119894120596=

119866lowast

119894120596320

116






119866prime

120596322


imaginary portion


























details here

117







119866prime =12058212057812059621205740

1 + 12058221205962 119866primeprime =

1205781205961205740

1 + 12058221205962323










Log

mo

dul

us


119866primeprime

119866prime

(a)


Log

mo

dul

us


119866prime

119866primeprime

(b)



118

















unit of rad





r


119

119888 =1

119905119886119899120572∙ Ω = 119872 ∙ Ω 324






(Mezger 2020)

120591119888 = (3

2120587 ∙ 1198771198623) ∙ 119879 325



120578(119888) =120591119888

119888= (

3 ∙ 119879

2120587 ∙ 1198771198623) ∙

120572

Ω326









α

Rc

Cone

Plate

Tested sample

Ω



120









No pre-shear








Table 316 and 317











Conditions for OFS


121










Table 318



Geometry gap


Equilibrium time


Creep Step

Controlled variable


Duration 30 minutes

Recovery Step

Controlled variable


Number of points



3621 Theory




122







et al 2013)







(Danley 2002)








Temperature

programmer

(∆T=0)

Reference Sample

Individual heaters

pans (with lids)

Platinum

resistance

thermomete

rs (TR)


Platinum

resistance

thermomete

rs (TS)

Controller ∆

P


123

36212 Heat flux DSC




















Reference Sample


T

S

T

R

Heat flux

plate

Pans (with lids)

Insulating

heat sink

Thermocouples

Material 1


(Chromel wire)

∆

T


124



applied



119902 =119889119867

119889119905= 119862119901

119889119879

119889119905+ 119891(119879 119905) 327

















Sample Reference T0

RS Rr

TS TR

qS qR

CS CR

Tzero

thermocouple


125



119902119878 =1198790 minus 119879119878

119877119878minus 119862119878

119889119879119878

119889119905328

119902119877 =1198790 minus 119879119877

119877119877minus 119862119877

119889119879119877

119889119905329




119902 = 119902119878 minus 119902119877 = minus∆119879

119877+ ∆1198790 (

1

119877119878minus

1

119877119877) + (119862119877 minus 119862119878)

119889119879119878

119889119905minus 119862119877

119889∆119879

119889119905330

∆119879 = 119879119878 minus 119879119877 331

∆1198790 = 1198790 minus 119879119878 332


















126










3631 Theory












Incident Light




127









∆θ =122120582

119889333



II

(θ) II

(θ)

Sin

θ

Sin

θ

a b

Laser Light source


Diffracted image

Incident Light




128
























Droplet size

Vo

lum

e d

ensi

ty (

)


129


















D[32] =sum 119899119894119889119894

3119899119894=1

sum 1198991198941198891198942119899

119894=1

334





D[32] = 11988932 =119889119907

3

1198891199042 335

119889119907 = (6119881119901

120587)

13

336

119889119904 = radic119860119901

120587337



130















desired result

1 Optical unit

2 Wet dispersion

unit

3 Wet cell


software


131









around 5 to 15











injected sample






(Singh 2002)


119907119900119897119906119898119890 119900119891 119904119886119898119901119897119890=

119898

119907338






the instrument

132


364 Microscopy








3651 Theory







Dispersant (Water)

Stirrer Speed (rpm)


Ultrasound Mode


Analysis





10



10

133











F

dx

L

Surface


134


















119865 = 2γL cos 120579 = γ ∙ 4πR ∙ cos 120579 339

γ =119865

119871 cos 120579340


135
























Liquid

rin

g θ

L

F

Liquid

F

Lamella

ring


136
















3661 Theory




















137


















Ion

source


r

record

er

Ionisati

on

Accelerati

on

Deflectio

n

Detectio

n

electromagnet

vacuum

Vaporised sample


138




















ioniser

sample

+

-

-

+ -

MS

1

- fragment

-

- - MS

2

detector


fragmentation

mz separation

detection


139


Cream




preparation




















determination





computer

140










filling










water bath







Conditioning Step



Pre-Shear No




141




determination test








test


Conditioning Step



Pre-Shear No











test





142


water bath


Conditioning Step




60 Duration (min)

5


Controlled variable


Frequency (Hz) 1






















143






















01

1

10

100

1000

10000

100000

1000000

10 100 1000

Vis

cosi

ty

Pa

S

Shear Stress Pa


144




















1

10

100

1000

10000

01 1 10 100

GG

P

a

Osc Stress Pa

G

G


145



















100

1000

10000

100000

0 20 40 60 80 100 120 140

G

G

Pa

Time min

G

G


146





















Conditioning Step




50 Duration (min)

5




147


Conditioning Step




50 Duration (min)

5



10-150


150-10






Table 46


Conditioning Step




50 Duration (min)

5









148




measurement)


Conditioning Step




50 Duration (min)

5























149





















001

010

100

1000

10000

100000

1000000

10000000

100000000

10 100 1000

Vis

cosi

ty P

a∙S

shear stress Pa


150




































151





















(380E-04 5412)

0

40

80

120

160

0 100 200 300 400 500

Sh

ear S

tress

P

a

Shear Rate s⁻sup1

Ramp Up

Ramp Down


152
















EV




10

100

1000

10000

001 01 1 10 100 1000

G

G

P

a


G

G


stress of 4 Pa

153









procedure










Dispersant (Water)

Stirrer Speed (rpm)



133


089

Analysis



Mie




10


01-20


10

154




















112 08

518 72

272 0

0

2

4

6

8

001 01 1 10 100 1000 10000

volu

me

den

sity

droplet size um

E45 without sles

E45 cream+2SLES


SLES

155














distribution













as reference cell







156






(5) Mark the cycle

















157












158










standard E45 cream















159


























160









in Table 51









513 814E+04

2738 365E+05

7924 219E+04

2506 187E+05

01

1

10

100

1000

10000

100000

1000000

1 10 100 1000

Vis

cosi

ty

Pa

S

Shear Stress Pa

E45


mimic cream




161


Product





E45 cream 2738 3288times105 5130 lt0211


2506 1704times105 7924 0407
























162
















explanation

SLES wt CA (wt)

GM (wt)

0 2 4 6

6 6

6 2

2 6

2 2


163


Formulation_Ⅰ
















obtained















164





















165

































166



[2 6 2] [4 6 2] [6 6 2]









264E+05

139E+05

600E+04

0

10

20

30

40

50

10E+01

50E+04

10E+05

15E+05

20E+05

25E+05

30E+05

262 462 662

yie

ld s

tress

Pa

Vis

co

sit

y P

as



yield stress


167





















amphiphiles
















168






value




























169

5106

1273254

07371

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()

[SLESCAGM] of [262]

G

G

Critical strain

8992

591542

07301

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()


G

8292

998696

09001

10

100

1000

10000

0001 001 01 1 10 100

G

G

Pa

strain ()

[SLESCAGM] of [662]

G

G

Critical strain

LVER

LVER

LVER

τy=24125

Critical strain

τy=33926



170


































171




































172













173

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ| P

as

G

G

P

a

Frequency Hz

[SLESCAGM] of [262]

G

G

|ƞ|

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ

| P

as

G

G

P

a

Frequency Hz


G

G

|ƞ|

1

10

100

1000

10000

100000

1

10

100

1000

10000

100000

001 01 1 10 100

|ƞ| P

as

G

G

P

a

Frequency Hz

[SLESCAGM] of [662]

G

G

|ƞ|



174



















01

1

10

100

1000

10000

100000

1000000

000001 0001 01 10 1000

Dyn

am

ic v

isco

sit

y co

mp

lex v

isco

sit

y P

as






175


















500

5000

50000

001 01 1 10 100

G

G

P

a

Frequency Hz

G-cream [2 6 2] G-cream [2 6 2]

G-cream [4 6 2] G-cream [4 6 2]

G-cream [6 6 2] G-cream [6 6 2]



176





























177















properties





02

04

06

08

001 01 1 10 100

Dis

sip

ati

on

facto

r (

tan

δ)

Frequency Hz

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]



178

















0

1

2

3

4

5

6

7

8

0 500 1000 1500 2000 2500 3000 3500 4000

J 1

0⁻sup3

Pa⁻

sup1

Time s

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]




179














Com

pli

ance

Time

O

A

B

C

D


Primary creep

Secondary creep

Residual compliance

Retardant recovery


E

G0 G1 Gi η0

τ0 η1

1

ηi



180


Formulation_Ⅰ




















181


















(a) (b)

(c)


182


Formulation_Ⅰ
















-4

-2

0

2

4

20 25 30 35 40 45 50 55 60 65 70 75 80

Hea

t Fl

ow

(N

orm

aliz

ed

) Q(W

g)


cetyl alcohol



183







-03

-02

-01

0

01

02

03

20 25 30 35 40 45 50 55 60 65 70 75 80

Hea

t Fl

ow

(N

orm

aliz

ed) Q

(W

g)


white soft paraffin




184















more mobile






-025

-020

-015

30 40 50 60 70

Heat

Flo

w Q

(Wg

)


262

462

662



185











[2 5 2] [2 6 2] [2 7 2]





















186



[4 5 2] [4 6 2] [4 7 2]























different systems

187




























188


Different Processes










Heating Procedure





















189









(min)


[2 6 2] [4 6 2] [6 6 2]






0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

2

4

6

8

10

12

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm




190

















0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm


0

3

6

9

12

15

01 1 10 100 1000

Volu

me

Den

sity

Diameter μm




191











[2 6 2] [4 6 2] [6 6 2]








[2 6 2] [4 6 2] [6 6 2]






192


Heating Procedure


















0

3

6

9

12

01 1 10 100 1000

Vo

lum

e D

en

sit

y

Diameter μm

Cream [2 6 2]500rpm

700rpm

900rpm



193











1

2

3

4

5

6

7

8

9

10


D[3

2] μ

m

Mixing speed

cream [2 6 2]

cream [4 6 2]

cream [6 6 2]


194





















A 200 20

B 200 5

C 300 10

D 200 10

E 0 10

195


Cooling Procedure

A B C D E

200rpm 20min

200rpm 5min

300rpm 10min

200rpm 10min

0rpm 10min

times105 η0






k -19923 -19405 -52341 -17865 -42169

01

1

10

100

1000

10000

100000

1000000

1 10 100 1000

Vis

cosi

ty

Pa

s

Shear stress Pa

200rpm20min

200rpm5min

300rpm10min

200rpm10min

0rpm10min



196




































197

100

1000

10000

100000

01 1 10 100

G

Pa

Frequency Hz

300rpm10min

200rpm10min

0rpm10min

100

1000

10000

100000

01 1 10 100

G

Pa

Frequency Hz

200rpm5min

200rpm10min

200rpm20min





198

















199












Oil

Media

SLs

Broth

SLs Cell pellet

Sedimentation

(a) (b)


200





















(a) (b)


201


















202










erucic acid (C22)











with C181

Diacylated acidic

SLs with C181

Diacylated acidic

SLs with C201


with C252

7333223

6873149


203













30

40

50

60

70

80

0 30 60 90 120 150 180 210 240 270 300 330

surfa

ce t

en

sion

(m

Nmiddotm

-1)



204














of biosurfactants

(a) (b)


205







MW 6704

MW 6564

MW 6964



206














structure of MELs

Possible fatty

acids chain

combinations

5352741 5343 MEL-D C81-80

6433460 6423 MEL-A C81-102

6573792 6564 MEL-BMEL-C C102-121C101-

122C81-142

6713578 6704 MEL-A C101-102C81-

122

6973735 6964 MEL-A C102-122

7133647 7124 MEL-BMEL-C C81-182C121-

142C121-

142C102-161

7313800 7304 MEL-A C101-140C120-

121C81-160

8956104 8946 MEL-A C183-183

9616177 9606 MEL-A C201-200

207


MELs











-025

-02

-015

-01

-005

0

005

01

015

02

-20 -10 0 10 20 30 40 50 60 70 80 90

Hea

t F

low

W

g

Temperature degC

ramp up

equilibrium

ramp down

equilibrium

ramp up

-025

-02

-015

-01

-005

0

005

01

015

02

-20 -10 0 10 20 30 40 50 60 70 80 90

Hea

t F

low

W

g

Temperature degC




208
















209



Formulation_Ⅲ






their performance










Configuration





configurations








210

















10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [2 6 2]

First Batch

Third Batch

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [4 6 2]

First Batch

Third Batch

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Cream [6 6 2]

First Batch

Third Batch



211

















Mixed Paraffin oils


(wt) GM

(wt)

2 4 6

6 2


2 4 6


oils-water system

212


































213




















214














228E+03

175E+03

222E+02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa


Cream [4MELs 6 2]

Cream [6MELs 6 2]



215






















216

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()


G

G

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()


G

G

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

0001 001 01 1 10

G

G

Pa

strain()


G

G



217






























218

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ

| P

as

G

G

Pa

Frequency Hz


G

G

|n|

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ

| P

as

G

G

Pa

Frequency Hz


G

G

|n|

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

|ƞ|

Pa

s

G

G

Pa

Frequency Hz


G

G

|n|



219






















10E+02

10E+03

001 01

G

G

Pa

Frequency Hz


G

G

10E+03

10E+04

10 100

G

G

Pa

Frequency Hz


G

G



220



et al 2018)



















221

10E+02

10E+03

10E+04

10E+05

001 01 1 10

G

G

P

a

Frequency Hz

Mixed Paraffin Oils




10E+02

10E+03

10E+04

001 01 1 10

G

G

P

a

Frequency Hz

Mixed Paraffin Oils






222




















0

005

01

015

02

025

03

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa

⁻sup1

Time s

Mixed Paraffin Oils

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

0

03

06

09

12

15

18

0 1000 2000 3000 4000

J

10

⁻sup2 P

a⁻sup1

Time s



223



















0

1

2

3

4

5

6

7

8

9

10

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa⁻sup1

Time s

Mixed Paraffin Oils

Cream [6MELs 6 2]

Cream [4MELs 6 2]

Cream [2MELs 6 2]



224

-04

-03

-02

-01

0

01

02

03

04

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

Wg

Temperature degC

Mixed Paraffin Oils

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

-04

-03

-02

-01

0

01

02

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

mW

mg

Temperature degC

Mixed Paraffin Oils

Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]



225
















Coconut Oil

SLES (wt) CA

(wt) GM

(wt)

2 4 6

6 2

2 4 6

SLES (wt)


226


















Coconut Oil


(wt) GM

(wt)

2 4 6

6 2


2 4 6



227









creep test









(wt) GM

(wt)

2 4 6

6 2


2 4 6


228






























229

205E+05

108E+05

546E+04

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

01 1 10 100 1000

vis

cosi

ty

Pas

Shear Stress Pa

Coconut Oils

Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]

276E+06

248E+05

130E+05

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

10E+07

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa


Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]





230



















181E+04167E+04

165E+04

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Coconut Oil

Cream [6SLs 6 2]

Cream [4SLs 6 2]

Cream [2SLs 6 2]



231



water system











stress





128E+05

271E+05

925E+05

100E-02

100E-01

100E+00

100E+01

100E+02

100E+03

100E+04

100E+05

100E+06

100E+07

01 1 10 100 1000

vis

cosi

ty

Pas

Shear Stress Pa


Cream [6SLs 6 2]

Cream [4SLs 6 2]

Cream [2SLs 6 2]



232














118E+05

171E+04

57E+03

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa

Coconut Oil

Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]



233



















639E+05

569E+05

214E+06

10E-01

10E+00

10E+01

10E+02

10E+03

10E+04

10E+05

10E+06

10E+07

01 1 10 100 1000

vis

cosi

ty

Pa

s

Shear Stress Pa


Cream [2MELs 6 2]

Cream [4MELs 6 2]

Cream [6MELs 6 2]



234





LVE range

00895

10E-02

10E-01

10E+00

10E+01

10E+02

10E+03

0001 001 01 1 10

G

G

Pa

strain()


G

G

0746510E-01

10E+00

10E+01

10E+02

10E+03

10E+04

0001 001 01 1 10 100

G

G

Pa

strain()


G

G





235











50E+01

50E+02

50E+03

50E+04

001 01 1 10 100

G

G

P

a

Frequency Hz

Coconut Oils






236

50E+01

50E+02

50E+03

50E+04

001 01 1 10 100

G

G

P

a

Frequency Hz





10E+02

10E+03

10E+04

10E+05

001 01 1 10 100

G

G

P

a

Frequency Hz

Coconut Oil







237

50E+01

50E+02

50E+03

50E+04

001 01 1 10

G

G

P

a

Frequency Hz

Coconut Oil




10E+02

10E+03

10E+04

10E+05

10E+06

001 01 1 10 100

G

G

P

a

Frequency Hz









238



















50E+01

50E+02

50E+03

50E+04

50E+05

50E+06

001 01 1 10

G

G

P

a

Frequency Hz







239























4 wt involved










(Nguyen et al 2015)

240




water system

241

















et al 2016)

0

01

02

03

04

05

06

07

08

09

1

0 500 1000 1500 2000 2500 3000 3500 4000

J

Pa

⁻sup1

Time s

Coconut Oil

Cream [2SLs 6 2]

Cream [4SLs 6 2]

Cream [6SLs 6 2]

0

2

4

6

8

0 1000 2000 3000 4000

J

10

⁻sup2 P

a⁻sup1

Time s


water system

242

-03

-02

-01

0

01

02

03

25 30 35 40 45 50 55 60 65 70

Heat

Flo

w

mW

mg

Temperature degC


Cream [2SLES 6 2]

Cream [4SLES 6 2]

Cream [6SLES 6 2]



243












244
































245





































246




































247




































248



SLES solution





























249

















250




















251


















252
















253

















254


















255




















256

















257


















258




















259



















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FORMULATION OF PERSONAL CARE PRODUCTS WITH BIO- …

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Transcript of FORMULATION OF PERSONAL CARE PRODUCTS WITH BIO- …