Starch Based Films
Transcript of Starch Based Films
8/19/2019 Starch Based Films
http://slidepdf.com/reader/full/starch-based-films 1/6
Effect of cellulose fibers addition on the mechanical properties andwater vapor barrier of starch-based films
Carmen M.O. Mu ller a,b, Joa o Borges Laurindo b,*, Fabio Yamashita a
a Department of Food Science and Technology, State University of Londrina, Londrina, PR, Brazilb Department of Chemical and Food Engineering, Federal University of Santa Catarina, Florianopolis, SC 88040-900, Brazil
a r t i c l e i n f o
Article history:
Received 2 October 2007
Accepted 12 September 2008
Keywords:
Starch films
Cellulose
Fibers
Mechanical
Water
Permeability
a b s t r a c t
Starch-based films have promising application on food packaging, because of their environmental appeal,
low cost, flexibility and transparency. Nevertheless, their mechanical and moisture barrier properties
should be improved. The aim of this work was to enhance these properties by reinforcing the films with
cellulose fibers. Besides, the influences of both the solubility coefficient of water in the films (b) and the
diffusion coefficient of water vapor through the films (Dw) on the films’ water vapor permeability (K w)
were investigated. Films were prepared by the so-called casting technique, from film-forming suspen-
sions of cassava starch, cellulose fibers (1.2 mm long and 0.1 mm of diameter), glycerol and water. The
influence of fibers addition on K w was determined at three relative humidity gradient ranges, DRH
(2–33%, 33–64% and 64–90%). Films reinforced with cellulose fibers showed higher tensile strength and
lower deformation capacity, and presented lower K w than films without fibers. K w showed strong
dependency of b and Dw, presenting values up to 2–3 times greater at DRH¼ 64–90% than at
DRH¼ 33–64%, depending on the film formulation. Therefore, adding cellulose fibers to starch-based
films is a viable alternative to improve their mechanical and water barrier properties. Besides, this work
showed the importance of determining film’s water vapor permeability simulating the real environ-
mental conditions the film will be used.
2008 Elsevier Ltd. All rights reserved.
1. Introduction
Starch production and industrialization represent a good alter-
native for developing countries (FAO, 2007). Developing new
products from this raw material can add value and expand its
industrial use. The production of biodegradable and edible films
from carbohydrates and proteins adds value to low cost raw
materials and can play an important role in food preservation
(Averous, Fringant, & Moro, 2001; Gennadios, 2002; Krochta &
Miller, 1997, among others). Preparing these films involves the use
of at least one film-forming agent (macromolecule), a solvent anda plasticizer. The most used macromolecules are polysaccharides
and their derivatives, proteins and lipids (Cuq, Gontard, & Guilbert,
1998; Krochta, 2002; Krochta & Mulder-Johnston, 1997).
Several studies reported the use of starches from different
sources to prepare films and coatings with different properties, and
had indicated that these carbohydrates are promising materials in
this regard (Averous et al., 2001; Larotonda, Matsui, Sobral, &
Laurindo, 2005; Mali, Grossmann, Garcıa, Martino, & Zaritzky,
2005; Mali, Sakanaka, Yamashita, & Grossmann, 2005). However,
films formed from starch are brittle and difficult to handle. Plasti-
cizers are normally added to the film-forming solution before
casting and drying procedures, as a way to overcome films brit-
tleness. Unfortunately, plasticizers generally decrease the film
water vapor permeability (Gontard, Guilbet, & Cuq,1993; Krochta &
Mulder-Johnston, 1997; Muller, Yamashita, & Laurindo, 2007).
In order to improve starch-based film characteristics, many
researches reported results on the addition of natural fibers as
a suitable reinforcing component for thermoplastic materials. Most
of these works focused on films’ mechanical properties and haveshowed that fibers incorporation increases films’ tensile strength
and elasticity modulus and decreases their elongation capacity
(Averous et al., 2001; Curvelo, de Carvalho, & Agnelli, 2001;
Dufresne & Vignon, 1998; Follain, Joly, Dole, Roge, & Mathlouthi,
2006; Gaspar, Benko, Dogossy, Reczey, & Czigany, 2005; Ma, Yu, &
Kennedy, 2005).
Concerning to the barrier properties, Dufresne and Vignon
(1998) and Funke, Bergthaller, and Lindhauer (1998) reported that
the addition of fibers decreased the water vapor permeability ( K w)
of starch-based films. This behavior was attributed to the low
hygroscopicity of cellulose fibers. In fact, the behavior of K w
depends on the simultaneous effect of water diffusivity in the* Corresponding author. Tel.: þ55 48 37219448; fax: þ55 48 37219687.
E-mail address: [email protected] (J.B. Laurindo).
Contents lists available at ScienceDirect
Food Hydrocolloids
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / f o o d h y d
0268-005X/$ – see front matter 2008 Elsevier Ltd. All rights reserved.doi:10.1016/j.foodhyd.2008.09.002
Food Hydrocolloids 23 (2009) 1328–1333
8/19/2019 Starch Based Films
http://slidepdf.com/reader/full/starch-based-films 2/6
polymeric matrix (Dw) and of the solubility coefficient of water in
the film (b) (Krochta & Miller, 1997; Larotonda et al., 2005; Muller
et al., 2007). Larotonda et al. (2005), working with Kraft paper
impregnated with starch acetate, investigated the influence of this
impregnation on the K w, Dw and b values of these materials. The
b value was calculated through the first derivative of the film water
sorption isotherm in relation to the water activity (aw), divided by
the water vapor pressure (at the sorption isotherm temperature).
As film’s K w is proportional to the product of b and Dw, the values of
Dw were determined from K w and b values, at three relative
humidity gradient ranges.
Moore, Martelli, Gandolfo, Sobral, and Laurindo (2006) studied
the influence of b and Dw on the water vapor permeability of
keratin films plasticized with glycerol and reported that the K w
valueincreased almost six times when 0.09 g glycerol/g keratin was
added. This result was explained by the high increase of b, while Dw
did not change significantly. Variability in the film thickness and
density were also reported as influencing the valuesof K w of keratin
films. Muller et al. (2007) reported results for starch-based films
that are qualitatively similar to results reported by the authors
above. For high relative humidity range, the b values increased 6-
fold for films with glycerol and 7-fold for films with sorbitol, while
Dw values did not change significantly. These results showed thatK w values are dependent on the solubility coefficient (b) of water in
the film. Results about the influence of fibers addition on the water
vapor permeability of starch films are rare in the literature (Imam,
Cinelli, Gordon, & Chiellini, 2005).
The films made in this work were supposed to be used as
packaging material. So, the aim of this work was to investigate how
the addition of cellulose fibers improves films’ mechanical and
moisture barrier properties and to verify howfibers addition affects
the relative influences of the solubility coefficient (b) and the
diffusion coefficient (Dw) on the water vapor permeability (K w) of
starch films. These results are not available in the literature and
very important to evaluate possible applications of these films as
packaging material.
2. Materials and methods
2.1. Films preparation
An aqueous suspension of fibers (softwood short fibers 1.2 mm
long and with 0.1 mm of diameter- Klabin S.A-Brazil) was prepared
cutting 10 g fiber and mixing with 400 ml of distilled water, in
order to facilitate the incorporation of these fibers to the starch
suspension. The films were prepared according to the so-called
casting technique. Film-forming solutions were prepared with 3%
w/w of cassava starch (Yoki - Brazil), 0.30 g glycerol/g dry starch,
0.01 g guar gum/g dry starch (to avoid fibers sedimentation) and
three concentrations of cellulose fibers: 0.10 (P10), 0.30 (P30) and
0.50 (P50) g of fiber/g dry starch. Fibers suspension, guar gum andwater were stirred for 10 min at 14,000 rpm in a dispenser, before
adding starch and glycerol. Afterwards, under constant stirring
(90 rpm), the container with the mixture was heated up until 80 C,
and the film-forming suspension was poured homogeneously in
acrylic Petri dishes 14 cm in diameter.The dishes with film-forming
mixture were then put in a ventilated oven, at 40 C, for 16 h. Films
prepared without fibers served as control.
2.2. Moisture, thickness and density
Prior to films’ properties determination, samples were condi-
tioned at 25 C and 58% relative humidity (RH) for 48 h. Films
moisture were determined in triplicate, by the gravimetric method,
after drying at 105
C for 24 h, and expressed in g water/g dry mass.Films thicknesses were measured (exactness of 0.001 mm) using
a Digimatic digital external micrometer (Mitutoyo Co., Japan) at ten
different points of the film. For determining film density, samples of
2 cm 2 cm were maintained in a desiccator with phosphorus
pentoxide (0% RH) for 20 days and weighed. Thus, dry matter
densities were calculated by Eq. (1).
rs ¼ m
A d (1)
where A is the film area (4 cm2), d the film thickness (cm), m the
film dry mass (g) and rs the dry matter density of the film (g/cm3)
(Larotonda et al., 2005). The film density was expressed as the
average of ten determinations.
2.3. Scanning electron microscopy (SEM)
Scanning electron microscopy (SEM) of film samples was
obtained using a Philips XL-30 scanning electron microscope. The
samples were coated with a fine gold layer before obtaining the
micrographs. All samples were examined using an accelerating
voltage of 10 kV.
2.4. Moisture sorption isotherms
Films’ moisture sorption isotherms were determined through
the static method, using saturated saline solutions to obtain
different relative humidities (Labuza & Ball, 2000). The Guggen-
heim–Anderson–de Boer (GAB) model (Eq. (2)) was used to
represent the experimental equilibrium data. In this equation the
parameter X w is the equilibrium moisture (g water/g dry mass), mo
is the monolayer water content, C is the Guggenheim constant,
which represents the sorption heat of the first layer and k is the
sorption heat of the multilayers. The GAB model parameters were
determined by non-linear regression, using the Statistica Software
6.0 (Statsoft, USA).
X w ¼ Ckmoaw
½ð1 kawÞð1 kaw þ CkawÞ (2)
2.5. Water vapor permeability (Kw)
Films’ water vapor permeabilities (K w) were determined in
appropriate diffusion cells (Sarantopoulos et al., 2002), using three
different ranges of relative humidity gradient (DRH¼ 2–33%,
DRH¼ 33–64% and DRH¼ 64–90%). The water vapor permeability
was determined using Eq. (3).
K w ¼ W d
Spsðaw1 aw2Þ (3)
where d is the average film thickness, S is the film permeation area
(0.005 m2), aw1 (RH1/100) is the water activity in the chamber, aw2
(RH2/100) is the water activity inside the cell, ps is the water vapor
pressure at the experimental system temperature (25 C) and
W ¼G/t (g of water/hour) wascalculated using the linear regression
of mass variation over time, under steady state permeation
condition.
2.6. Water solubility coefficient (b) and effective water
diffusion coefficient (Dw)
The solubility coefficient of water in the films, b (g of water/g of
dry mass Pa), was determined according to Larotonda et al.
(2005), based on the experimental moisture sorption isotherms,GAB model and Eq. (4).
C.M.O. Muller et al. / Food Hydrocolloids 23 (2009) 1328–1333 1329
8/19/2019 Starch Based Films
http://slidepdf.com/reader/full/starch-based-films 3/6
b ¼ Ckmo
ps
" 1
ð1 kawÞð1 kaw þ CkawÞ
aw
½ð1 kawÞð1 kaw þ CkawÞ2½ kð1 kaw þ CkawÞ
þ ð1 kawÞðk þ CkÞ
# (4)
where C , mo and k are the adjust parameters of GAB model and b is
given in g of water/g of dry solid Pa.
The water diffusion coefficients through the films were deter-
mined from water vapor permeability, water solubility coefficient
in the film and film density data. As b varies with aw, the value
correspondent to the aw median was used in Eq. (5).
K w ¼ rsbDw (5)
2.7. Mechanical properties
Films’ mechanical properties were determined from tension
tests, using the TA-XT2i texture analyzer (Surrey – England), in
accordance with ASTM-882-00 (2000). The dimensions of film
samples used in tests were 25 mm 100 mm, cut with a sharp
scissor. Samples were clamped between grips and force and
deformation were recorded during extension at 50 mm/min, with
an initial distance between the grips of 50 mm. In this way, tensile
strength (MPa), elasticity modulus (MPa) and relative deformation
at break (%) were determined from ten replicates for each film
formulation.
2.8. Statistical analysis
Analysis of Variance (ANOVA) and Tukey mean comparisontest ( p 0.05) were performed (Statistica Software – Statsoft, OK –
USA).
3. Results and discussions
3.1. Moisture, thickness and density of the films
The incorporation of cellulose fibers reduced the films moisture
(Table 1), due to the lower water affinity of cellulose fibers
compared with starch (Curvelo et al., 2001; Dufresne & Vignon,
1998; Funke et al., 1998; Ma et al., 2005). There was no significant
difference among the thicknesses, which varied from 110 11 mm
to 12118 mm. On the other hand, fibers incorporation caused
a significant reduction of film density, e.g., the film P50 presenteddensity 1.8 times lower than the film without cellulose fibers,
which can be explained by the low density of the cellulosic material
(Dufresne & Vignon, 1998; Wollerdorfer & Bader, 1998).
3.2. SEM – scanning electron micrographies
Micrographies of films’ surfaces and fractures (Fig. 1) showed
homogeneous and random distributions of fibers within the
samples, without pores or cracks formation. It can also be observed,
from the fractured films micrographies, that cellulose fibers are
incrusted in the continuous starchy material.
3.3. Moisture sorption isotherms
The GAB model fitted well the films’ sorption data ( Table 2), as
previously reported by other authors (Godbillot, Dole, Joly, Roge, &
Mathlouthi, 2006; Mali, Sakanaka, et al., 2005; Martelli, Moore,
Paes, Gandolfo, & Laurindo, 2006, among others). All isotherms
presented sigmoidal shape (Fig. 2), which is a characteristic of
starchy materials, but the curves’ ‘‘shoulders’’ (close to aw ¼ 0.03)
were reduced as the fiber concentration in the films increased. The
water sorption isotherm of cellulose fibers shows clearly their
lower hygroscopicity. The P10 film presented equilibrium moisture
similar to the ones observed for the films without fibers. For the
last, the hygroscopicity increased due to the presence of guar gum,
which probably balanced the opposite effect provoked by the
cellulose fibers. According to Chaisawang and Suphantharika(2005, 2006) the addition of guar gum (1%) to cassava starch causes
a larger absorption of water, due to hydrocolloids interaction with
the amylose chain. These results are in agreement with results
reported by other researchers who worked with composites of
starch and cellulosefibers (Averous et al., 2001; Curvelo et al., 2001;
Dufresne & Vignon, 1998; Ma et al., 2005). Averous et al. (2001)
reported that wheat starch films reinforced with cellulose fibers
had their equilibrium moisture reduced. They attributed this
behavior to the interactions between fibers and the hydrophilic
sites of starch chain, which substituted the starch–water interac-
tions that predominate in films without fibers. The effect of fibers
on films’ hygroscopicity can also be observed from the monolayer
water content data, mo, which was 0.094 g water/g solid for films
without fibers against 0.058 g water/g solid for films with 0.50 g of fiber/g of starch. On the other hand, the k value was not affected by
film composition (fiber addition).
3.4. Influence of relative humidity gradient (DRH) range and fibers
concentration on the water vapor permeability (Kw), solubilitycoefficient (b) and effective water diffusion coefficient (Dw)
For all samples K w values increased as the DRH range moved
from lower to higher values (Table 3). For the DRH ranges of 2–33%
and 64–90%, K w of P50 films presented values approximately 3.7
and 1.5 times lower if compared with starch films without fibers
(WF). However, at the intermediate gradient (33–64%), water vapor
permeabilities of WF films and P50 were of the same order
(3.43107
and 3.08 107
g/h m Pa). For the P30 formulation theK w value was about 10 times higher when the DRH range passed
from 2–33% to 64–90%. This result can be explained by the
increasing of 8.3 times observed for the solubility coefficient b,
Table 1
Moisture, thickness and density of starch films reinforced with different concentrations of cellulose fibers.
Samples Moisture (g water/g dry solid) Thickness (mm) Density 106 (g/m3)
WF 0.120 0.006a 111 11a 2.41 0.12a
P10 0.115 0.002b 111 8a 1.47 0.08b
P30 0.107 0.004c 111 13a 1.32 0.08bc
P50 0.090 0.002d 121 18a 1.31 0.03c
a,b,c,d Values with the same letter at the same column are not different statistically ( p< 0.05).
WF – without fibers.P50, P30 and P10 denote 0.50, 0.30 and 0.10 g fibers/g starch, respectively.
C.M.O. Muller et al. / Food Hydrocolloids 23 (2009) 1328–13331330
8/19/2019 Starch Based Films
http://slidepdf.com/reader/full/starch-based-films 4/6
while the diffusion coefficient Dw did not change considerably (only
22% higher).
The b value of all formulations increased as the DRH range
moved from 2–33% to 64–92%. Fig. 3 shows that for water activities
lower than 0.10 the b value was very influenced by aw, i.e.,b decreased very quickly with the aw increase. From aw values
between 0.10 and 0.60, b was practically constant, but became very
responsive to aw when aw > 0.60.
Film densities decreased from 2.41 to approximately
1.3103 g/m3 due to cellulose fibers addition, which influenced
the values of K w
, accordingly to Eq. (5).The DRH rangedidnotaffect a lot the Dw values of films without
fibers, indicating that in this case the K w increasing was conse-
quence of the increment of b . The WF-film’ permeability was 4.5
times higher at the DRH ¼ 64–90% than at DRH¼ 2–33%, due to the
big increase of b (about 6 times), while Dw did not change
considerably.
The values of Dw for P10, P30 and P50 did not present appre-
ciable change, except at intermediate DRH range (33–64%). For P30
samples, when DRH passed from 2–33% to 33–64%, the K w
increased 5.6 times, due to the simultaneously increase of
b (2 times) and Dw (2.8 times). Under these DRH conditions, both
coefficients b and Dw had about the same influence on the K w
values.
For the DRH ranges of 2–33% and 64–90% the addition of cellulose fibers provoked decreasing of K w from approximately 10
Fig. 1. Scanning electron microscopy of cassava starch films with cellulose fibers. P50, P30 and P10 denote 0.50, 0.30 and 0.10 g fibers/g starch, respectively and the upper index s
and f denote surface and fracture, respectively.
Table 2
GAB model fitted parameters for sorption data from cassava starch films with
incorporation of cellulose fibers.
Sample GAB parameters R2
mo (g water/g solid) k C
WF 0.094 0.928 322.22 >0.99
P10 0.087 0.959 127.74 >0.99
P30 0.073 0.965 80.51 >0.99
P50 0.058 0.982 65.87 >0.99
Cellulose fibers 0.029 0.877 9.65 >0.99
WF – without fibers.P50, P30 and P10 denote 0.50, 0.30 and 0.10 fibers/g starch, respectively.
C.M.O. Muller et al. / Food Hydrocolloids 23 (2009) 1328–1333 1331
8/19/2019 Starch Based Films
http://slidepdf.com/reader/full/starch-based-films 5/6
to 5.7 gm/m2 h Pa. It was due mainly to the film density reduction
from 2.410.12 to 1.31 0.03106 g/m3 and to a small reduction
of the b values. For the DRH¼ 33–64% the addition of fibers did not
affect K w appreciably, which could be explained by the small vari-
ation of b and Dw with the addition of cellulose fibers (Fig. 3, Table
3). The reduced density of films reinforced with cellulose fibers
could reduce K w, but it was not observed.
In a general manner, similar behavior of K w, b and Dw with RH
range was reported for keratin films (Moore et al., 2006) and Kraft
paper impregnated with starch acetate (Larotonda et al., 2005) and
were explained by the effect of RH range on the parameters b and
Dw. However, the mass transfer mechanisms controlling the barrier
properties of reinforced films can change with DRH range and
cellulose fiber concentration and cannot be evidenced from globalproperties as sorption isotherms and water vapor permeability. For
this purpose, techniques as confocal laser scanning microscopy
could be very useful to investigate microstructure and water
distribution in composite-films with different formulations (Chen,
Lee, & Teoh, 2007; Straadt, Rasmussen, Andersen, & Bertram, 2007).
3.5. Mechanical properties
Films reinforced with fibers presented higher values of tensile
strength and elasticity modulus, and lower values of tensile
strength (deformation at break) (Fig. 4), if compared with WF films.
This behavior is in agreement with the results reported in the
literature about starch films reinforced with different kinds of
fibers (Averous & Boquillo, 2004; Curvelo et al., 2001; Funke et al.,
1998; Gaspar et al., 2005; Lu, Weng, & Cao, 2006).
The incorporation of 0.10 and 0.50 g fiber/g starch increased the
tensile strength of reinforced films in 6.7 and 18 times, respectively.
The elasticity modulus of P10 and P50 films were, respectively, 7.6
and 34 times greater than the elasticity modulus of WF films. This
significant increasing of films rigidity has been attributed to the
similarity between the chemical structures of cellulose and starch
(Ma et al., 2005).
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
aw
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
X w ( g
w a t e r / g d r y s o l i d )
P10 P30 P50 Cellulose fibersWF
Fig. 2. Water sorption isotherms of cassava starch films with cellulose fibers fitted
with the GAB model. P50, P30 and P10 denote 0.50, 0.30 and 0.10 g fibers/g starch,
respectively.
Table 3
Water vapor permeability (K
w
), solubility coefficient (b) and diffusion coefficient(Dw) of cassava starch films with cellulose fibers incorporation as a function of the
relative humidity gradient (RH).
aw Gradients Samples K w 107 (gm/m2 h Pa) b 106 (g/gPa) Dw 108 (m2/h)
0.02–0.33 WF 2.33 0.13 1.78 5.30
0.33–0.64 3.43 0.24 2.91 4.65
0.64–0.90 10.3 0.18 10.6 3.93
0.02–0.33 P10 0.85 0.08 1.40 4.13
0.33–0.64 4.23 0.19 2.96 9.72
0.64–0.90 8.32 0.72 12.1 4.68
0.02–0.33 P30 0.67 0.01 1.27 4.00
0.33–0.64 3.78 0.13 2.53 11.3
0.64–0.90 6.87 0.09 10.5 4.96
0.02–0.33 P50 0.64 0.09 1.06 4.61
0.33–0.64 3.08 0.14 2.11 11.1
0.64–0.90 5.74 0.26 9.41 4.66
WF – without fibers.P50, P30 and P10 denote 0.50, 0.30 and 0.10 g fibers/g starch, respectively.
0,0 0,2 4,0 0,6 0,8 1,0
aw
0,00
2E-5
4E-5
6E-5
8E-5
1E-4
β ( g
w a t e r
/ g d r y s o l i d s . P a ) Cellulose fibers
P50
Fig. 3. Solubility coefficient values (b) for cassava starch films with cellulose fibers
(P50) and cellulose fibers as a function of water activity ( aw).
0
5
10
15
20
25
30
WF P10 P30 P50
Samples
T e n s i l e s t r e n g t h ( M P a )
0
20
40
60
80
100
120
P er c en t el on g a t i on
a t b r e ak ( % )
Tensile strength
Elongation
0
200
400
600
800
WF P10 P30 P50
Samples
Y o u n g ´ s M o d u l e ( M P a
)
a
b
Fig. 4. (a) Tensile strength and percent elongation at break of cassava starch films with
cellulose fibers incorporation. (b) Young’s modulus of cassava starch films with
cellulose fibers incorporation. WF denotes without fibers films, while P50, P30 and P10denote 0.50, 0.30 and 0.10 g fibers/g starch, respectively.
C.M.O. Muller et al. / Food Hydrocolloids 23 (2009) 1328–13331332
8/19/2019 Starch Based Films
http://slidepdf.com/reader/full/starch-based-films 6/6
4. Conclusions
Films’ water vapor permeability have strong dependency on
solubility and water diffusion coefficients and, consequently, on
relative humidity gradient range, presenting values up to 2–3 times
greater at 33–64% than at 64–90%, depending on film formulation.
Therefore, it is important to determine this property based on the
environmental conditions the film will be used.
The incorporation of cellulose fibers reinforces mechanically
starch films, which have higher tensile strength and lower defor-
mation capacity. The reinforced films present lower water vapor
permeabilities if compared with starch films without fibers. As
cellulose fibers are biodegradable and available at low cost, their
use as reinforcing agent is a viable alternative to improve the
properties of starch-based films.
Acknowledgements
This research was supported by CAPES and MCT/CNPq-Brazil.
References
ASTM – American Society for Testing and Materials. (2000). Standard test method for tensile properties of thin plastic sheeting . ASTM D882-00. Philadelphia: ASTM.8 p.
Averous, L., & Boquillo, N. (2004). Biocomposites based on plasticized starch:thermal and mechanical behaviours. Carbohydrate Polymers, 56 , 111–122.
Averous, L., Fringant, C., & Moro, L. (2001). Plasticized starch–cellulose interactionsin polysaccharides composites. Polymer, 42, 6565–6572.
Chaisawang, M., & Suphantharika, M. (2005). Effects of guar gum and xanthan gumadditions on physical and rheological properties of cationic tapioca starch.Carbohydrate Polymers, 61, 288–295.
Chaisawang, M., & Suphantharika, M. (2006). Pasting and rheological properties of native and anionic tapioca starch as modified by guar gum and xanthan gum.Food Hydrocolloids, 20, 641–649.
Chen, F., Lee, C. N., & Teoh, S. H. (2007). Nanofibrous modification on ultra-thinpoly(epsilon-caprolactone) membrane via electrospinning. Materials Science & Engineering C – Biomimetic and Supramolecular Systems, 27 (2), 325–332.
Cuq, B., Gontard, S., & Guilbert, S. (1998). Protein as agriculture polymers forpackaging production. Cereal Chemistry, 75, 1–9.
Curvelo, A. A. S., de Carvalho, A. J. F., & Agnelli, J. A. M. (2001). Thermoplastic starch-
cellulosicfiberscomposites: preliminary results.CarbohydratePolymers, 45,183–188.Dufresne, A., & Vignon, M. R. (1998). Improvement of starch film performancesusing cellulose microfibrils. Macromolecules, 31, 2693–2696.
FAO, Food and Agriculture Organization of the Unites Nations. http://www.fao.org/page/boletin.htp. Accessed 23.06.07.
Follain, N., Joly, C., Dole, P., Roge, B., & Mathlouthi, M. (2006). Quaternary starchbased blends: influence of fourth component addiction to the starch/water/glycerol system. Carbohydrate Polymers, 63, 400–407.
Funke, U., Bergthaller, W., & Lindhauer, M. G. (1998). Processing and characteriza-tion of biodegradable products based on starch. Polymer Degradation andStability, 59, 293–296.
Gaspar, M., Benko, Z., Dogossy, G., Reczey, K., & Czigany, T. (2005). Reducing waterabsorption in compostable starch-based plastics. Polymer Degradation andStability, 90, 563–569.
Gennadios, A. (2002). Protein-based films and coatings. Boca Raton, USA: CRC Press.646 pp.
Godbillot, L., Dole, P., Joly, C., Roge , B., & Mathlouthi, M. (2006). Analysis of waterbinding in starch plasticized films. Food Chemistry, 96 , 380–386.
Gontard, N., Guilbert, S., & Cuq, J. L. (1993). Water and glycerol as plasticizers affectmechanical and water vapor barrier properties of an edible wheat gluten films. Journal of Food Science, 58, 206–211.
Imam, S. H., Cinelli, P., Gordon, S. H., & Chiellini, E. (2005). Characterization of biodegradable composite films prepared from blends of poly(vinyl alcohol),cornstarch, and lignocellulosic fiber. Journal of Polymers and the Environment, 13,47–55.
Krochta, J. M. (2002). Protein as raw materials for films and coating: definitions,current status and opportunities. In A. Gennadios (Ed.), Protein-based films andcoating (pp. 1–32). Boca Raton, USA: CRC Press.
Krochta, J. M., & Miller, K. S. (1997). Oxygen and aroma barrier properties of ediblefilms: a review. Trends in Food Science and Technology, 8, 228–237.
Krochta, J. M., & Mulder-Johnston, C. (1997). Edible and biodegradable polymerfilms: challenges and opportunities. Food Technology, 51, 61–74.
Labuza, T. P., & Ball, L. N. (2000). Moisture sorption – Practical aspects of isothermmeasurement and use (2nd ed.). American Association. pp. 35–45.
Larotonda, F. D. S., Matsui, K. N., Sobral, P. J. A., & Laurindo, J. B. (2005). Hygro-scopicity and water vapor permeability of Kraft paper impregnated with starchacetate. Journal of Food Engineering, 71, 394–402.
Lu, Y., Weng, L., & Cao, X. (2006). Morphological, thermal and mechanical propertiesof ramie crystallites-reinforced plasticized starch biocomposites. CarbohydratePolymers, 63, 198–204.
Mali, S., Grossmann, M. V. E., Garcıa, M. A., Martino, M. N., & Zaritzky, N. E. (2005).Mechanical and thermal properties of yam starch films. Food Hydrocolloids, 19,157–164.
Mali, S., Sakanaka, L. S., Yamashita, F., & Grossmann, M. V. E. (2005). Water sorptionand mechanical properties of cassava starch films and their relation to plasti-cizing effect. Carbohydrate Polymers, 60, 283–289.
Martelli, S. M., Moore, G., Paes, S. S., Gandolfo, C., & Laurindo, J. B. (2006).Influence of plasticizers on the water sorption isotherms and water vaporpermeability of chicken feather keratin films. LWT – Food Science and Tech-nology, 39, 292–301.
Ma, X., Yu, J., & Kennedy, J. F. (2005). Studies on the properties of natural fibers-reinforced themoplastics starch composites. Carbohydrate Polymers, 62, 19–24.
Moore, G. R. P., Martelli, S. M., Gandolfo, C., Sobral, P. J. A., & Laurindo, J. B. (2006).Influence of the glycerol concentration on some physical properties of featherkeratin films. Food Hydrocolloids, 20, 975–982.
Muller, C. M. O., Yamashita, F., & Laurindo, J. B. (2007). Evaluation of the effect of glycerol and sorbitol concentration and water activity on the water barrierproperties of cassava starch films through a solubility approach. Carbohydrate
Polymers. doi:10.1016/jcarbpol.2007.07.026.Sarantopoulos, C. I. G. L., Oliveira, L. M., Padula, M., Coltro, L., Alves, R. M. V., &Garcia, E. E. C. (2002). Embalagens plasticas flexıveis: Principais polımeros eavaliaçao de propriedades. Campinas, Brazil: CETEA/ITAL. 267 pp.
Straadt, I. K., Rasmussen, M., Andersen, H. J., & Bertram, H. C. (2007). Aging-inducedchanges in microstructure and water distribution in fresh and cooked pork inrelation to water-holding capacity and cooking loss – a combined confocal laserscanning microscopy (CLSM) and low-field nuclear magnetic resonance relax-ation study. Meat Science, 75, 687–695.
Wollerdorfer, M., & Bader, H. (1998). Influence of natural fibres on mechanicalproperties of biodegradable polymers. Industrial Crops and Products, 8, 105–112.
C.M.O. Muller et al. / Food Hydrocolloids 23 (2009) 1328–1333 1333