Properties and permeability of aroma compounds in food through plasticized cassava films

International Food Research Journal 16: 97-103 (2009)
Properties and permeability of aroma compounds in food
through plasticized cassava films
Boonsong, P., *Laohakunjit, N., Kerdchoechuen, O. and Tusvil, P.
School of Bioresources and Technology, King Mongkut’s University of Technology Thonburi
Bangkhuntien Bangkok, Thailand 10150
Abstract: The properties and permeability of aroma compounds in food through the cassava starch films
was investigated. Films were prepared by 5% starch and properties of the films were monitored at different
concentration of two plasticizers; glycerol and sorbitol. Sorbitol-cassava starch films showed a better
transmission rate (water vapor or/and oxygen), and had a higher mechanical properties; tensile strength and
elongation, than those glycerol-cassava starch films. 35% sorbitol-cassava starch films was the best film which
had the best mechanical properties, low tensile strength and high elongation. Thus, the 35% sorbitol-cassava
starch film was further studied for permeation of aroma compounds in foods (cinnamaldehyde, cis-jasmone,
benzyl benzoate, eugenol, 1,8-cineol, limonene, 2,4,6-trimethylpyridine (TMP)). Permeability of aroma
compounds was determined by measuring the steady-state flux (J) of both static and dynamic systems. Results
showed that benzyl benzoate had the lowest J values demonstrating that the cassava starch films revealed the
lowest permeable to this aroma compounds probably due to absorbed, adsorbed, covalently linked, and trapped
mechanism.
Keywords: Cassava, starch, film, permeability, aroma compound
Introduction
material and edible starch film is frequently used as
matrix material which gelatinized starch forms can
Biopolymer films have several advantages over interact with other molecules (Reineccius, 1991).
polymeric packaging such as mild processing, easily Edible films can also be plasticized by low molecular
modifiable physical properties, biodegradability weight carbohydrates, such as polyols (Stading et
and recyclable raw materials. The potential usage al., 2001; Mathew and Dufresne, 2002; Talja et al.,
of edible film is for coatings or wrapping various 2007). The addition of a plasticizing agent to edible
kinds of foods, fruits, meats and candies. It has been films is required to overcome film brittleness caused
suggested as a matrix material for controlled release by extensive intermolecular forces. The plasticizers
and encapsulation active agent such as flavors, also increase polymer chain mobility, improving
perfumes, essential oils, herbicides, pesticides and flexibility and extenseibilityof the film, and diffusion
pheromones (Dziezak, 1988; Gennadios and Weller, coefficients and generally lead to increased gas and
1990; Shahidi and Han, 1993; Atterholt et al., 1998) water vapor permeability (Huang et al., 2006). In
which are made available at a desired site, time, and films manufactured from whey protein isolate
at a specific rate (Pothakamury and Barbosa-Canovas, (WPI), increasing levels of glycerol and sorbitol
1995). The main function of edible film could be to have been reported to increase film permeability and
prevent mass transfer of water or other compounds, extensibility and reduce film strength (McHugh and
such as oxygen, carbon dioxide, oil and aroma Krochta, 1994). In Shaw et al. (2002) studied on
compounds, between a product and surroundings or WPI, they proposed the effects of glycerol, xylitol,
between different layers of a product (Huang et al., and sorbitol to film properties. Increasing glycerol or
2006).
sorbitol content led to increase in moisture content,
Edible films can be prepared from biomaterials water vapor permeability, and % elongation; and
such as polysaccharides and proteins (Banker, 1966; decrease in tensile strength, elastic modulus, and
Kester and Fennema, 1986). Starch is a low cost glass transition temperatures of films (Laohakunjit
*Corresponding author.
Email: nutta.lao@kmutt.ac.th, orapin.ker@kmutt.ac.th
© All Right Reserved

---

98
Boonsong, P., Laohakunjit, N., Kerdchoechuen, O. and Tusvil, P.
and Noomhorm, 2004). Although increasing levels Switzerland. A starch used was cassava starch, of
of xylitol have no effect on permeability, moisture Thaiwa Company, Thailand, purchased at a local
content, and glass transition temperatures of the films, market in Thailand. Starch samples were passed
%elongation, tensile strength, and elastic modulus through a 100-mesh sieve. D(-)sorbitol was obtained
decreased (Shaw et al., 2002).
from Merck, Germany. Glycerol was obtained from
Aroma compounds may be dissolved, absorbed AnalaR, U.K.
or adsorbed, covalently linked, trapped, encapsulated
and limited in their diffusion as a result of the presume Preparation of cassava starch films
of food components (Langourieux and Crouzet,
Cassava starch films were prepared by weighing 5
1994). There are several mechanisms explained for g of cassava starches, followed by the addition of 100
the transfer process of small molecule with starch. mL of demineralized water. Glycerol (10, 15, 20, 25,
Many experiments and analytical techniques have 30% (w/w)) and sorbitol (15, 20, 25, 30, 35% (w/w))
been developed to study the interaction of starch dry starch were added to the water-starch mixtures
with flavor and aroma compounds (Godshall and (Laohakunjit and Noomhorm, 2004). Gelatinization
Solms, 1992). The transfer of compounds within of the starch suspensions was performed by heating
the product and their release from its depends on the the mixtures on a hot plate under continuous mixing
functional group of the aroma compound in foods with a magnetic stirrer. During the gelatinization
such as alcohol (eugenol, 1,8-cineol), ester (benzyl procedure, the beaker was covered with watch glass
benzoate), aldehyde (cinnamaldehyde), ketone aluminum foil in order to avoid excessive evaporation
(cis-jasmone), alkene (limonene), pyridine (2,4,6-
of water. Films were obtained by casting the
trimethylpyridine; TMP), the composition and the gelatinized starch solutions into acrylic blocks (width
structure of the matrix (Seuvre et al., 2006; Habeych 17 cm x length 21 cm) and adjusting the thickness (2
et al., 2007). Edible films are mainly hydrophilic, mm). Films were subsequently dry overnight at 60°C
and sorption of aroma compound in foods is reduced at over water bath. Properties analysis of cassava
compared to that of apolar plastic packaging (Willige, starch films were water vapor transmission rate
2002), resulting in smaller permeability of aroma (WVTR) (g.mm/m2/day) by the dish method ASTM
compounds through edible films. Thus, aroma barrier E 96 (ASTM, 1995), oxygen transmission rate (OTR)
of traditional packaging could be improved with (cm3.µm/m2/d.KPa) by the standard method ASTM
edible coating films. The purposes of these studies D1434-82 (ASTM, 1992), tensile strength (TS)
were to investigate the properties of cassava starch (MPa) and elongation properties (%) by the standard
film and permeability of aroma compounds in foods method ASTM D 882-97 (ASTM, 1997).
through plasticized cassava starches films.
Determination of the flux of the aroma compounds
through the films
Materials and methods
The determination of the flux of the aroma
compounds through the films was performed using
Chemicals
glass beaker as chamber (diameter = 2.3 cm, height =
Standard substances such as cinnamaldehyde, 3.2 cm) equipped with a sample container and a cover,
cis-jasmone, benzyl benzoate, eugenol, 1,8-
in which the films were fitted. The chamber was filled
cineol, limonene, TMP were obtained from Fluka, with around 0.5 g of aroma compounds represented

Film
GC-FID
Inlet carrier gas
(Nitrogen)
Closed by septum
Figure 1. Permeation cell
International Food Research Journal 16: 97-103

---

Properties and permeability of aroma compounds in food through plasticized cassava films
99
Table 1. Water vapor transmission rate (WVTR), oxygen transmission rate (OTR), tensile strength
(TS) and elongation properties of cassava starch films as affected by plasticizer type (glycerol and
sorbitol) and concentration.
concentration of
WVTR
OTR
TS
elongation
plasticizer
plasticizer (%
(g.mm/m2/
(cm3.µm/m2
(MPa)
(%)
w/w)
day)
.d kPa)
cassava starch
films
0
1239
27.41
3.62
1.1
10
849
23.84
2.97
1.07
15
1204
nd
2.84
1.33
glycerol-
cassava starch
20
1231
24.78
2.60
1.38
films
25
1378
nd
2.38
1.52
30
1577
30.98
2.16
1.70
15
595
nd
3.88
2.71
20
638
3.08
2.61
7.22
sorbitol-
cassava starch
25
666
nd
1.43
29.42
films
30
785
3.69
1.38
30.07
35
947
5.23
1.05
30.07
nd means not detect
by 7 chemical compounds; cinnamaldehyde, cis-
therefore, equals the experimentally determined
jasmone, benzyl benzoate, eugenol, 1,8-cineol, solubility of the volatile in the different films) (Yilmaz
limonene, TMP. The chamber was covered with the et al., 2004).
suitable plasticized cassava starch film (diameter =
2.3 cm). All connection parts were coated by wax. Determination of aroma compounds vapor
The chambers were subsequently kept in a desiccator permeability
which contained silica gel and magnesium sulphate for
Dynamic measurement method of volatile vapor
desicant. The weight of the chamber was determined fluxes through films or membranes was performed.
daily for nine days, and compared with not covered The permeation cell (Figure 1), composed of two
with cassava starch film. From the steady-state flux chambers which was divided by the film was adapted
(J) expressed in mg/cm2 .h, the diffusion coefficient for the study. Area of cassava starch film exposed
(D) expressed in cm2/h of the volatile in the starch to perform was 491.6 cm2. The two chambers were
matrix was calculated using Fick’s first law:
continuously swept by a 30 ml/min nitrogen gas
flow. Aroma in the vapor phase on the down-side of
J = D.?C/h
the cell were obtained by mixing two flows: aroma
compounds; cinnamaldehyde, cis-jasmone, benzyl
Where h is the thickness of the film in cm, ?C benzoate, eugenol, 1,8-cineol, limonene, TMP and
(mg/cm3) is the concentration difference between the nitrogen gas. The upper-side of the cell was obtained
two sides of the film (?C is equal to the concentration by nitrogen gas flow. Two milliliter of outgoing flow
of the aroma compounds at the lower end (receiving from upper-side of the cell was injected at initial
side) of the film, since the concentration the upper time, 4, 6 and 8 hours in a gas chromatography-flame
end (exciting side) is assumed to be zero, and ?C, ionizing detector (GC-FID) by using DB-WAX
International Food Research Journal 16: 97-103

---

100 Boonsong, P., Laohakunjit, N., Kerdchoechuen, O. and Tusvil, P.
Table 2. Steady-state flux (J) of various aroma compounds through cassava starch films
measured by the static system.
steady-state flux (mg cm-2 h-1)
volatile compound
covered with film
not covered with film
benzyl benzoate
0.011e
0.102c
eugenol
0.015e
0.116c
1,8-cineol
0.041de
0.112c
cis-jasmone
0.074cd
0.247b
cinnamaldehyde
0.100c
0.322a
limonene
0.176b
0.332a
TMP
0.239a
0.342a
F-test
**
**
C.V. (%)
22.614
8.413
LSD
0.050
0.045
a,b,c Means with the same letter are not significantly different at 5%, LSD. Means + standard deviation.
column. Conditions of GC-FID were helium and plasticized films compared to unplasticized film was
nitrogen (both used flow 70 kPa) for carrier gas. Air due to the hypothesis of hydrogen bonding between
zero and hydrogen (flow 50 and 60 kPa, respectively) hydroxyl groups of polyols and starch which decreases
were gas for flame. Injector temperature 200°C, oven free sorption sites for water in polyol plasticized films
temperature 40°C, hold 1 min and increased from 40°C (Aurand and Woods, 1973; Le Bot and Gouy, 1995;
to 240°C by rate 10°C/min hold 1 min and detector Talja et al., 2007). WVTR of films was depended
temperature 230°C (Debeaufort and Voilley, 1994). on both solubility coefficient and diffusion rate of
The experimental design was set up in Completely water in film and they were also depended on partial
Randomized Design (CRD) with 3 replications. All pressure of water vapor (Kester and Fennema, 1986).
data were analyzed using the SAS General Linear The OTR of plasticized films determined at 23ºC, 0%
Model, Mean separation was performed by protected RH had a lower value than unplasticized film because
LSD method at P ? 0.05.
the network micro-structure changed to decrease
pore size of plasticized films (Kester and Fennema,
1986). Plasticization of edible films was believed to
Results and discussion
disrupt intermolecular interactions between polymer
molecules with the effect of decreasing brittleness and
Table 1 showed properties of cassava starch increasing film flexibility (Lieberman and Guilbert,
films such as water vapor transmission rate (WVTR) 1973). Decrease in film strength and increase in ability
(g.mm/m2/day), oxygen transmission rate (OTR) to elongate with increasing glycerol and sorbitol
(cm3.µm/m2/d.KPa), tensile strength (TS) (MPa) content, indicated by decreasing tensile strength, and
and elongation properties (%) were similar way of increasing %elongation values, might be attributed
both plasticizers. Glycerol- and sorbitol-cassava to a reduction in the number of intermolecular cross-
starch film at the higher plasticizer content had links between polymerized starch molecules within
greater transmission properties. The lower WVTR of films (Gontard et al., 1993). The good properties of
International Food Research Journal 16: 97-103

---

Properties and permeability of aroma compounds in food through plasticized cassava films
101
Table 3. Steady-state flux (J) of various aroma compounds through cassava starch films measured by
the dynamic system using a permeation cell.
volatile compound
steady-state flux (mg cm-2 h-1)
benzyl benzoate
1.55f
cinnamaldehyde
3.03d
1,8-cineol
4.71b
eugenol
2.16e
cis-jasmone
3.37c
limonene
4.45b
TMP
6.99a
F-test
**
C.V. (%)
5.376
LSD
0.296
a,b,c Means with the same letter are not significantly different at
5%, LSD. Means + standard deviation.
plasticized cassava starch films were low WVTR, from low to high, respectively. Cassava starch film
OTR value, and tensile strength but high %elongation could decreased permeation of aroma compounds
values. The results of comparison between glycerol- because the amylose network of cassava starch
and sorbitol-cassava starch films were shown that film could prevent diffusion of aroma compounds,
transmission properties of sorbitol were greater than reduce pore size of film, and make aroma compounds
glycerol. Because sorbitol consists of high hydroxy difficult to permeation (McHugh and Krochta, 1994).
groups compared to glycerol, greater transmission Permeation properties of aroma compounds were
properties were originating from hydrogen bonding depended on the molecule weight, boiling point and
between hydroxyl groups of sorbitol starch films than structure that could make the rate of volatilization
those glycerol films. At low concentration of sorbitol, of aroma compounds (Gallo et al., 1998). Benzyl
transmission properties were good but mechanical benzoate showed the lowest J values demonstrating
properties (TS and elongation) were poor. The best that the cassava starch films was lowest permeable to
propertiy of films (good transmission properties and this aroma compounds probably due to high molecule
flexibility) were found in cassava starch film added weight (212.25), high boiling point of the compound
with 35% sorbitol, which WVTR (947 g.mm/m2/
(323°C), absorbed, adsorbed, covalently linked, and
day), OTR (5.23 cm3.µm/m2/d.KPa), tensile strength trapped mechanism. Moreover, the most important
(10.29 MPa) and elongation (30.07%). In agreement factor in a polymer film was the forces between the
with Krochta and de Mulder (1997), they disclosed permeated molecule (Piringer, 2000; Nestorson et
that good properties of edible films were WVTR at al., 2007). Fornasiero et al. (2005) reported that the
10-100 g.mm/m2/day, OTR at 1-10 cm3.µm/m2/d.KPa, rate of permeation of small compounds through a
tensile strength at 10-100 MPa and high elongation. polymeric matrix was affected by the size and their
Thus, cassava starch film with 35% sorbitol was used physical-chemical affinity to the polymer. A common
for permeation of aroma compounds in the next study approach used to describe the diffusion through
of permeation of aroma.
matrices was the solution-diffusion model (Fornasiero
Permeation of aroma compounds through cassava et al., 2005), where the polymeric-matrix/solute
starch film was shown in Table 2. Permeation of system was considered to be a molecular solution
benzyl benzoate, 1,8-cineol, eugenol, cis-jasmone, in which solute transport is through diffusion only
cinnamaldehyde, limonene and TMP was found (Habeych et al., 2007). Other factors affected the
International Food Research Journal 16: 97-103

---

102 Boonsong, P., Laohakunjit, N., Kerdchoechuen, O. and Tusvil, P.
permeability were the volatility and molar volume of References
the aroma compounds (Nestorson et al., 2007). Table
3 showed that the steady-state fluxes of particular the ASTM. 1992. Standard methods for oxygen transmission
compounds through the cassava starch film utilizing
of material. In Annual Book of ASTM Standards.
the vapor permeability measurements method.
American Society for Testing and Materials.
Permeability of TMP by dynamic system was highest
Philadelphia. PA.
at 6.99 mg/cm2.h but permeability of 1,8-cineol, ASTM. 1995. Standard methods for water vapor
limonene, cis-jasmone, cinnamaldehyde, eugenol and
transmission of material. In Annual Book of ASTM
benzyl benzoate were lower at 4.71, 4.45, 3.37, 3.03,
Standards. American Society for Testing and Materials.
2.16, and 1.55 mg/ cm2. h, respectively. Permeation
Philadelphia. PA.
of 7 compounds in dynamic system showed similar
pattern as the static system which TMP resulted in ASTM. 1997. Standard test methods for tensile properties
the highest permeation and benzyl benzoate showed
of thin plastic sheeting. In Annual Book of ASTM
the lowest permeation. This finding indicated that
Standards. American Society for Testing and Materials.
there was no different between permeability by static
Philadelphia. PA.
and dynamic systems of aroma compounds through
plasticized cassava films. From the above data Atterholt, C.A., Delwiche, M.J., Rice, R.E. and Krochta,
J.M. 1998. Study of biopolymers and paraffin
it could also be seen that the permeation of aroma
as potential controlled release carriers for insect
compounds through cassava starch film depended
pheromones. Journal of Agricultural and Food
on film properties (good transmission properties and
Chemistry 46: 4429-4434.
flexibility), physicochemical characteristics of aroma
compounds (volatility, molecule weight, and boiling Aurand, L.W. and Woods, A.E. 1973. Food Chemistry. In
point) and interaction between aroma compounds, and
Aurand, L.W. and Woods, A.E. (Eds), 363 p. The AVI
cassava starch films (absorbed, adsorbed, covalently
Publishing Company: Westport, Connecticut.
linked, and trapped mechanism).
Banker, G.S. 1966. Film coating theory and practice.
Journal Pharmaceutical Sciences 55: 81.
Conclusion
Beerler, A.D. and Finney, D.C. 1983. Plasticizers, In
Modern Plastics Encyclopedia. McGraw-Hill: New
The study of plasticizer-cassava starch film
York.
properties were found that higher plasticizer contents
increased transmission properties, the film structure Debeaufort, F. and Voilley, A. 1994. Aroma compound
was soften and sticky, low tensile strength and
and water vapor permeability of edible films and
high elongation. 35% sorbitol-cassava starch films
polymeric packaging. Journal of Agricultural and
showed that 35% sorbitol had greater properties in
Food Chemistry 42 (12): 2871-2875.
low WVTR, OTR, and low tensile strength, but high
%elongation compared with 30% glycerol-cassava Dziezak, J. D. 1988. Microencapsulation and encapsulated
ingredients. Food Technology 4: 136-159.
starch films.
The permeation of aroma compounds Fornasiero, F., Krull, F., Prausnitz, J.M. and Radke, C.J.
(cinnamaldehyde, cis-jasmone, benzyl benzoate,
2005. Steady state diffusion of water through soft-
eugenol, 1,8-cineol, limonene, TMP) through
contact-lens materials. Biomaterials 26 (28): 5704-
sorbitol-cassava starch films was found that
5716.
permeability of aroma compounds was determined
by measuring the steady-state flux (J) by the static Gallo, J.A.Q., Debeaufort, F. and Voilley, A. 1998.
and dynamic systems. Permeation of benzyl
Interactions between aroma and edible films. 1.
benzoate showed the lowest J values. On the other
Permeability of methyl cellulose and loe-density
hand, cassava starch film decreased the permeation
polyethylene films to methyl ketones. Journal of
Agricultural and Food Chemistry 47(1): 108-113.
of aroma compounds. Permeation ability varied due
apparently to differences in properties of the aroma Gennadios, A. and Weller, C.L. 1990. Edible film and
compounds. The improvement of flavor and edible
coating from wheat and corn properties. Food
film interaction would be the subject of continuing
Technology 44: 63-68.
studies.
International Food Research Journal 16: 97-103

---

Properties and permeability of aroma compounds in food through plasticized cassava films
103
Godshall, M.A. and Solms, J. 1992. Flavor and sweetener
Nestorson, A., Leufven, A. and Jarnstrom, L. 2007. Control
interaction with starch. Food Technology 46 (6): 142-
of aroma permeability in latex coatings by altering
145.
the vinyl acid content and the temperature around T .
g
Polymer Testing 26: 916-926.
Gontard, N., Guilbert, S. and Cuq, J.L. 1993. Water and
glycerol as plasticizers affect mechanical and water
Piringer O. 2000. Permeation of gases, water vapor and
vapor barrier properties of edible wheat gluten films.
volatile organic compounds. In Baner A.L. (Ed.).
Journal of Food Science 58(1): 206-211.
Plastic Packaging Materials for Food: Barrier Function.
Mass Transport, Quality Assurance and Legislation, p.
Habeych, E., Goot, A.J. and Boom, R. 2007. Prediction
239-285. Wiley-VCH: Weinhein.
of permeation fluxes of small volatile components
through starch-based films. Carbohydrate Polymers
Pothakamury, U.R. and Barbosa-Canovas, G.V. 1995.
68: 528-536.
Fundamental aspects of controlled release in food.
Trends in Food Science and Technology 6: 397-406.
Huang, C.B., Jeng, R., Sain, M., Saville, B.A. and Hubbes,
M. 2006. Production, characterization, and mechanical
Reineccius, G.A. 1991. Carbohydrates for Flavor
properties of starch modified by Ophiostoma spp.
Encapsulation. Food Technology 45(3): 144-146,
BioResources 1(2): 257-269.
149.
Kester, J.J. and Fennema, O.R. 1986. Edible films and
Seuvre, A.M., Philippe, E., Rochard, S. and Voilley,
coatings: A review. Food Technology 40(12): 47-59.
A. 2006. Retention of aroma compounds in food
matrices of similar rheological behaviour and different
Krochta, J. M. and de Mulder, J.C. 1997. Edible and
compositions. Food Chemistry 96 (1): 104-114.
biodegradable polymer films - challenges and
opportunities. Food Technology 51(2): 61-74.
Shahidi, F. and Han, X. Q. 1993. Encapsulation of food
ingredients. Critical Reviews in Food Science and
Langourieux, S. and Crouzet, J. 1994. Interaction
Nutrition 33 (6): 501-547.
between polysaccharides and aroma compounds. In
G. Charalmabus (Ed.), Food Flavors: Generation,
Shaw, N.B., Monahan, F.J., O’Riordan, E.D. and
Analysis and Process Influence, p. 1173-1199. Elsevier
O’Sullivan, M.O. 2002. Physical properties of WPI
Science Publishers. United Kingdom:
films plasticized with glycerol, xylitol, or sorbitol.
Journal of Food Science 67 (1): 164-167.
Laohakunjit, N., and Noomhorm, A. 2004. Effect of
plasticizers on mechanical and barrier properties of
Stading, M., Rindlav-Westling, A. and Gatenholm, P. 2001.
rice starch film. Starch/Stake 56 (8): 348-356.
Humidity induced structural transitions in amylose
and amylopectin films. Carbohydrate Polymers 45 (3):
Le Bot, Y. and Gouy, P.A. 1995. Handbook of starch
209-217.
hydrolysis products and their derivatives. In Kearsley,
M.W. and Dziedzic, S.Z. (Eds). p. 155-177. Blackie
Talja, R.A., Helen, H., Roos, Y.H. and Jouppila, K. 2007.
Academic and Professional: New York
Effect of type and content of binary polyol mixtures
on physical and mechanical properties of starch-based
Lieberman, E.R. and Guilbert, S.G. 1973. Gas permeation
edible films. Carbohydrate Polymers 71: 269-276.
of collagen films as affected by cross-linkage,
moisture, and plasticizer content. Journal of Polymer
Willige R.W.G. 2002. Effects of flavour absorption on foods
Science 41: 33-43.
and their packaging materials, 140 p. Wageningen
(Netherlands): Wageningen University.
Mathew, A.P. and Dufresne, A. 2002. Plasticized waxy
maize starch: Effect of polyols and relative humidity
Yilmaz, G., Jongboom, R., Feil, H., Dijk, C.V. and Hennink,
on material properties. Biomacromolecules 3(5):
W.E. 2004. Permeation of volatile compounds through
1101-1108.
starch films. Biomacromolecules 5: 650-656.
McHugh, T.H. and Krochta, J.M. 1994. Sorbitol- vs
glycerol-plasticized whey protein edible films:
Integrated oxygen permeability and tensile property
evaluation. Journal of Agricultural and Food Chemistry
42 (4): 841-845.
International Food Research Journal 16: 97-103

---