RESEARCH ARTICLE

Effect of shearing on functional properties of starches isolatedfrom Indian kidney beans

Seeratpreet Kaur, Amritpal Kaur, Narpinder Singh and Navdeep Singh Sodhi

Department of Food Science and Technology, Guru Nanak Dev University, Amritsar, India

Starches suspensions from four kidney bean lines (varying in amylose content) were sheared for

different intervals (0–8 min) at 15 000 rpm at 258C. Starches were then evaluated for granule size

distribution, thermal, rheological, and structural properties. Shearing caused an increase in

amylose content, paste viscosities, and small size granules containing granular fragments.

Transition gelatinization temperatures: Onset temperature (To), peak temperature (Tp), conclusion

temperature (Tc), crystallinity, and short-order range decreased upon shearing. Native starches

from different lines showed unimodal and trimodal granules distribution. A change in size

distribution from trimodal to unimodal was observed in starch upon shearing, starch with higher

amylose content showed greater effects. Shearing of starches caused disintegration and frag-

mentations of granules that made them to gelatinize at lower temperature.

Received: August 23, 2012

Revised: December 5, 2012

Accepted: December 5, 2012

Keywords:

Kidney bean / Pasting / Rheological / Shearing / Thermal

1 Introduction

Starch is a versatile and useful polymer because of the ease

with which its physicochemical properties can be altered

through chemical, enzymatic, or physical treatment to pro-

vide special functionality to the end products [1]. The pro-

portion of amylose and amylopectin as well as fine structure

of amylopectin varies in starch from different sources. Pulse

starches characterize to have higher amount of amylose and

have C-type structure [2]. The starch granules of pulses have

greater stability against mechanical shear than those of the

fragile swollen starches because of the hot paste viscosity that

does not show any breakdown point in pulses. Kidney bean

starch vary in amylose content, granule size distribution, and

higher resistance to swelling and rupturing, which makes

them more viscous than cereal starches. Kidney bean starch

also vary in proportions of long- and short chains of amylo-

pectin [3].Starch is often sheared or homogenized with other

ingredients during processing. The intense mechanical

shearing may affect the structure, pasting, and thermal prop-

erties. Shearing affected the integrity of the starch granules

that leads to the change in the properties of the product

during processing [4]. Breakage of the granules is dependent

upon granule strength and shear forces applied. If the impact

forces are larger than the granule strength, continuous break-

age and immediate coalescence of the granules takes place.

When the granule strength exceeds the impact forces, gran-

ules will not break. Native starches are highly sensitive to

heating and shear forces that affect the integrity of starch

granules, leading to a decrease in the viscosity of the product

during the process.

Physical condition like high speed and shearing affect the

quality parameters of the final product. Therefore, it is

important to study how shearing affected the properties of

the starch which ultimately affect the food quality. Therefore,

present investigation was carried out to see the effect of

shearing on particle size distribution, thermal, and pasting

properties of kidney bean starch varying in amylose content.

2 Materials and methods

2.1 Materials

Four kidney bean (Phaselous vulgaris) germplasm (EC498445,

EC540796, PI339501, and PI204719) was obtained from

Correspondence: Professor Narpinder Singh, Department ofFood Science and Technology, Guru Nanak Dev University,Amritsar 143005, IndiaE-mail: narpinders@yahoo.comFax: þ91-183-2258820

DOI 10.1002/star.201200180808 Starch/Starke 2013, 65, 808–813

� 2013WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.starch-journal.com

National Bureau of Plant Genetic Resources Regional Station,

Phagli, Shimla, India, in the year 2006–2007.

2.2 Methods

2.2.1 Isolation of starch

The isolation of starch was carried out using a procedure

described earlier in [3]. Kidney beans (100 g) were steeped

overnight in toluene solution (2.2 mL/500 mL distilled water)

at 408C. The beans were then washed with tap water, peeled,

and then ground with distilled water (1:10). The slurry was

then passed through a nylon cloth to remove fiber and the

residue obtained was again ground with distilled water and

the slurry was then allowed to stand for 2–3 h. The super-

natant was then discarded. Washing was continued until the

supernatant became clear followed by centrifugation and then

dried at 408C.

2.2.2 Preparation of sheared starch

Twenty percent starch suspension at 258C was sheared using

IKAT25 Digital Ultra-Turrax Homogenizer 2, 4, and 8 min at

15 000 rpm. Starch slurry was then centrifuged at 3000 rpm

for 10 min. Starch was separated and dried at 408C. Samples

were then evaluated for various properties.

2.2.3 Amylose content

Amylose content of starch was determined by using the

method of [5] from a standard curve developed using different

proportions of amylose and amylopectin. Sample (20 mg) was

solublized in 1 N KOH (5 mL) and was allowed to stand at

room temperature for 30 min to facilitate complete solubli-

zation. Volume was thenmade upto 100 mLusing volumetric

flask. Ten milliliters of the stock solution was then taken in

50 mL volumetric flask and 5 mL 0.1 N HCl was added.

Iodine solution (0.5 mL; 1:10, I2:KI) was added and volume

was made up with distilled water. Color development was

finally measured at 625 nm using spectrophotometer.

2.2.4 Pasting properties

The pasting properties of starch sheared for different

durations were evaluated using Rheoplus (Anton Parr,

Molecular Compact Rheometer, Model MCR302) from differ-

ent kidney bean lines. Starch (3 g sample in 25 mL distilled

water) was weighed directly in the aluminium sample canis-

ter and distilled water was added to a total constant sample

weight 28 g. The samples were sheared at 160 rpm through-

out the experiment. A programmed heating and cooling was

used where samples were held at 508C for 1 min, heated to 958Cin 7.5 min, held at 958C for 5 min, cooling from 95 to 508C in

7.5 min, and holding at 508C for 2 min. Parameters recorded

were pasting temperature, peak viscosity, trough viscosity,

breakdown viscosity, setback viscosity, and final viscosity.

2.2.5 FTIR spectroscospy

The crystalline structures of the native and sheared starches

were determined using Vertex70 FTIR (Bruker, Germany). All

the samples were kept in dessicator over P2O5 under vacuum

for at least 2 weeks until constant weights were obtained

before spectra were taken. Spectra of an empty cell were

taken as background using wavelength from 800 to 2000/

cm with 4/cm resolution using OPUS software. All spectra

were the averages of 200 scans. The absorbance intensities of

the bands at 1047, 1035, and 1022/cm were used to evaluate

the crystalline structures of native and sheared starches.

2.2.6 Thermal properties

Thermal properties were analyzed using a DSC-822 (Mettler

Toledo, Greinfense, Switzerland), equipped with a thermal

analysis data station. Starch sample (3 to 3.5 mg) was weighed

into a 40 mL capacity aluminium pan (Mettler, ME-27331) and

distilled water was added with the help of Hamilton micro-

syringe to achieve a starch water suspension containing 70%

water w/w. Pans were sealed and allowed to stand for 1 h at

room temperature before heating in DSC. The analyzer was

caliberated using indium and empty aluminium pan was

used as reference. Sample pans were heated at a rate of

108C/min from 30 to 1008C. Onset temperature (To), peaktemperature (Tp), conclusion temperature (Tc), and enthalpy

of gelatinization (DHgel) were calculated for endotherms

using Stare software for thermal analysis ver 8.10.

2.2.7 Particle size distribution

Particle size distribution of the starches was measured by

laser scattering using a Malvern Mastersizer Hydro 2000S,

(Malvern Instruments Ltd.,UK). The sample was added to the

sample port to reach an obscuration to �40%. The size

distribution was expressed in terms of the volumes of equiv-

alent spheres.

2.2.8 Dynamic rheometry

Twenty percent starch suspension was prepared in distilled

water after stirring for 30 min. The storage modulus (G0) of

aqueous starch suspensions were measured using a Haake

Rheostress-600 (Thermo Electron, Germany) rheometer

using parallel plate geometry (35 mm). The gap size, strain,

and frequency were set to 1 mm, 1% and 1.0 rads, respect-

ively. The starch samples were heated from 50 to 908C at a rate

of 0.58C/min and held at 908C for 10 min and then cooled

down to 508C. G0908C, G0

holding at 908C, and G0508C were

measured.

Starch/Starke 2013, 65, 808–813 809

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2.2.9 Statistics analysis

Each experiment was performed in triplicate unless otherwise

stated, and data were expressed as mean � SD in Fig. 1.

3 Results and discussion

3.1 Amylose content

Sheared starches from different lines except PI204719

showed higher amylose content as compared to their native

starch. PI339501 starch showed greater change in apparent

amylose content (42.24 to 46.20%) as shearing duration

increased from 0 to 8 min whereas PI204719 showed the

lowest change (from 35.83 to 35.90%). This increase may be

attributed to the breakage and fragmentation of starch gran-

ules during high speed shearing for varying durations. The

mechanical forces caused disintegration of starch granule.

The strong mechanical forces during shearing have been

reported to cause rupturing and damage of starch granules

[6].

3.2 Pasting properties

Effect of shearing on various pasting properties (peak

viscosity, setback, breakdown viscosity, final, and pasting

temperatures) is shown in Fig. 2. Sheared starches from

different lines showed higher peak viscosity as compared

to their native starches. PI204719 showed an increase from

2845 to 7346 cP upon shearing for 8 min while the least

change in EC540796 starch (from 2474 to 3069 cP) under

similar shearing conditions was observed. The increase in

peak viscosity with shearing may be attributed to the disrup-

tion of granules that expose more sites for hydroxyl groups

which may have increased the swelling of granules [7]. The

variation in change in peak viscosity caused by shearing

amongst different kidney bean lines may be attributed to

differences in their granular rigidity. Breakdown viscosity

of the sheared starches from different lines was higher as

compared to native starches. PI204719 starch showed the

greatest increase in breakdown viscosity (from 340 to

2047 cP) with shearing (8 min), and the least change in

EC540796 starch (from 587 to 692 cP) under similar shearing

conditions was observed. Sheared starches from different

lines showed higher setback viscosity as compared to their

native starches and the effect of shearing was prominent in

PI339501 starch. PI204719 starches showed progressively

increased setback with increase in shear duration.

EC498445 and EC540796 starches did not show significant

change in setback as shearing duration was increased from 2

to 8 min. The increase in setback value with shearing may be

attributed to faster and greater leaching of amylose due to

fragmentation of granules. Broken granules produced during

shearing resulted in higher water uptake and retention lead-

ing to higher pasting viscosity. Pasting temperature of

sheared starches from different lines except PI204719 was

lower as compared to their counterpart native starches.

EC498445 showed the highest change in pasting temperature

caused by shearing. EC498445 native starch showed pasting

temperature of 80.658C against 77.258C for counterpart

8 min sheared starches. Lower pasting temperature of

sheared starch may be attributed to their higher swelling

caused by the presence of disrupted granules that gelatinized

at lower temperatures.

3.3 FTIR spectroscospy

Crystalline structure and short-range order was analyzed using

the infrared spectrum within range of 800–1200/cm [8].

Amorphous structure is related to infrared absorbance band

at 1047/cm whereas short-range order is related to infrared

absorbance band at 1022/cm. The short-range order is

Figure 1. (a) Effect of shearing on crystallinity of starch. (b) Effectof shearing on ratio of the 1047/1022 cm�1 and 1047/1035 cm�1

intensities of kidney bean starches.

810 S. Kaur et al. Starch/Starke 2013, 65, 808–813

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defined as helical order, which is related to the crystallinity of

starch. The IR absorption band at 1047 and 1022/cm is related

to crystalline and amorphous structure, respectively. Shoulder

obtained at 1037/cm characterizes the presence of short-

range order. The ratios between intensities of 1047/1022

and 1047/1035/cm were used to describe the change in

crystallinity and short-range order, respectively [9]. The shearing

resulted in a decrease in ratio of band intensities of both 1047/

1022 and 1047/1035/cm indicating decrease in crystallinity as

well as short-range order (Fig. 1a,b). The ratio between inten-

sities of 1047/1022/cm for native starches ranged between 0.72

and 0.75, which decreased between 0.56 and 0.69 in starches

when sheared for 8 min. Earlier ratio between intensities of

1047/1022/cm for pea, lentil, and chickpea starches between

0.91 and 0.94, 0.92 and 0.93, and 0.86 and 0.89, respectively

were reported [10]. These differences may be due to the differ-

ence in amylose content and sources of starches.

3.4 Thermal properties

Transition temperatures (To, Tp, Tc) and enthalpy of gelatini-

zation (DHgel) decreased with increase in shearing duration.

Sheared starches showed lower transition temperature (To,Tp, and Tc) and gelatinization enthalpy as compared to their

native starch. Lower transition temperatures of sheared

starches indicated the beginning of gelatinization at lower

temperature. The change in To and Tp caused by shearing varyin starches from different lines. The highest decrease in Tocaused by shearing for 8 min was observed for PI204719

(66.90 to 64.988C) starch while EC540796 starch (70.18 to

69.638C) showed the least change. The highest decrease in Tpcaused by shearing was in EC498445 starch (75.26 to 72.088C)and the lowest in PI204719 starch (72.28 to 71.98C) after

similar shearing. The change in transition temperatures

and enthalpy of gelatinization may be attributed to change

in starch structure as shearing has been reported to increase

the amorphous regions of the starch granules while weaken-

ing and decreasing the crystalline regions of the starch [11–

13]. The ratios between intensities of 1047/1022/cm was

observed to lower in sheared starches reflecting presence

of lower crystallinity. Shearing of starch caused a significant

change in DHgel. EC498445 sheared starch showed the great-

est decrease in Tc (81.78 to 77.048C) as compared to other

lines. Sheared starches showed lower DHgel than their native

starches. PI339501 starch showed the greatest decrease in

DHgel (9.0 to 7.38 J/g) after shearing. Shearing break the

granules and the resultant starch may require lesser energy

to gelatinize as compared to native starch. Increasing the

Figure 2. Effect of shearing on pasting properties of starches.

Starch/Starke 2013, 65, 808–813 811

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shearing duration from 2 to 8 min did not cause any signifi-

cant change in DHgel. EC498445 starch showed the greater

changes in transition temperatures after shearing as compare

to other lines.

3.5 Particle size distribution

The size of the starch granules in different lines ranged

between 0.55 and 180 mm. Different lines showed unimodal

and trimodal distribution profiles for the granules size

(Fig. 3). EC498445 starch showed unimodal particle size

distribution with peak at �11–30 mm. Shearing of starch

broke the granules into smaller particles, thus change the

granule size distribution. Sheared starches showed the pres-

ence of small size granules (<1 mm), which were absent in

native starches. This indicated that shearing caused disinteg-

ration of large granules, though the effects vary in starch from

different lines. EC498445 starch sheared for 8 min showed a

decrease in the proportion of large size granules (�35–

60 mm) from 21.04 to 17.21% and increase in the proportion

of small size granules (�11–30 mm) containing fragmented

granules from 73.03 to 82.62%. EC498445 starch sheared for

2 min did not show presence of any small size granules,

however after shearing for 4 and 8 min small size granules

(�1 mm) and granular fragments appeared. The appearance

of theses granules may be attributed to the breaking and

fragmentation of large size granules during shearing into

small size granules. PI339501 starch showed trimodal particle

size distribution with first peak at �1–10 mm, second peak at

�11–30 mm, and third peak at �120–200 mm. PI339501

starch showed presence of large size granules (�65–

120 mm, �120–200 mm). Shearing resulted in the disappar-

eance of large size granules (�65–120 mm, �120–200 mm).

Shearing of PI339501 starch for 2 min caused an increase in

the proportion of small size granules (�11–30 mm) and

granular fragments from 56.25 to 74.06% and a decrease

in the proportion of large size granules (�35–60 mm) from

24.45 to 15.98%. PI339501 starch sheared for 4 min further

increased the proportion of small size granules containing

fragmented granules. PI339501 starch sheared for 8 min

showed an increase in proportion of small size granules

(�1 mm, �1–10 mm, �11–30 mm from 1.23 to 1.47%, 3.86

to 4.15%, 56.25 to 74.06%, respectively). PI204719 starch

showed unimodal particle size distribution with peak at

11–30 mm, when sheared for 8 min an increase in the pro-

portion of granule of size�11–30 mm (from 76.38 to 81.44%)

and decrease in the proportion of granules of size �35–

60 mm (from 23.14 to 18.45%) was observed. EC540796

starch showed bimodal distribution with first peak at �11–

30 mm and second peak at �65–120 mm. EC540796 sheared

02468

101214161820

0.1 1.0 10.0 100.0

Size (µm)

Volu

me

of G

ranu

les

(%)

EC-4984452mins

Control

8mins

0

4

8

12

16

20

0.1 1.0 10.0 100.0Size (µm)

Volu

me

of G

ranu

les

(%)

EC-540796

Control

2mins8mins

0

4

8

12

16

20

0.1 1 10 100 1000Size (µm)

Volu

me

of G

ranu

les

(%)

PI-339501

Control

2mins8mins

0

4

8

12

16

20

0.1 1 10 100Size (µm)

Volu

me

Of G

ranu

les

(%) PI-204719

Control

2mins8mins

Figure 3. Effect of shearing on particle size distribution.

812 S. Kaur et al. Starch/Starke 2013, 65, 808–813

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starch showed an increase in the proportion of granule size

�1 mm (from 1.13 to 1.38%), �1–10 mm (3.56 to 4.17%),

�11–30 mm (55.16 to 73.46%) and decrease in the proportion

of granules of size �35–60 mm (from 24.05 to 20.90%).

EC540796 native starch showed presence of large size gran-

ules (�65–120 mm, �120–200 mm), which disappeared after

shearing. The disappearance may be attributed to the break-

ing of large size granules into smaller size granules. Results

revealed that shearing affected the size range and proportion

of the granules. However, increasing the shearing duration

did not bring any significant change.

3.6 Dynamic rheology

The rheological parameters of native and sheared starches

during heating (50 to 908C), holding (at 908C for 10 min), and

cooling (90 to 508C) were studied. The sheared starches

showed lower G0908C than their native counterparts in all

the four kidney bean lines studied. However, among the

starches from different kidney bean lines, PI339501 sheared

starch showed higher decrease (887 to 395 Pa) in G0908C as

compared to other starches after shearing for 8 min whereas

PI204719 starch showed lowest decrease in G0908C from 454

to 406 Pa after similar shearing durations. Shearing led to

disintegration of the starch granules causing fast and early

swelling which resulted in decreased viscosity. During hold-

ing at 908C for 10 min, G0908C decreased in both native and

sheared starches. Sheared starches showed greater decrease

in G0908C as compared to their native starch. PI-339501

sheared starch showed higher decrease in G0908C during

holding for 10 min (from 440 to 251 Pa) at 908C as observed

in sheared starches from other lines. G0 was also measured

during cooling from 90 to 508C (G0508C). Shearing caused a

decrease in G0 in all the starches. PI204719 starch showed

higher decrease in G0508C after shearing for 8 min (from 795

to 270 Pa) as compared to other starches. PI339501 sheared

starch showed the lowest decrease inG0508C after shearing for

8 min (469 to 291 Pa).

4 Conclusions

Shearing of starches caused disintegration and fragmentation

of large size granules into small size granules that vary in

different Kidney bean lines. Shearing resulted in an increase

in amylose content, paste viscosities and small size granules,

and a decrease in gelatinization temperatures. The disinteg-

ration of granules reduced the crystallinity as well as short-

range order that caused the starch to gelatinization at lower

temperature.

Financial assistance to N. S. from Department Science andTechnology, Ministry of Science and Technology, Govt. of India,and CSIR-SRF to S. K. is acknowledged.

The authors have declared no conflict of interest.

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