Jung Han. Innovations in Food Packaging
Подождите немного. Документ загружается.
Lipid-based edible
films
and coatings
375
WVP
of the thinnest film (3.8 pm) was about 20 times its value for films of
14.7-37.1 pm thickness. These researchers explained that very thin films stretch more
when peeled from the drying surfaces. They also observed that the HPMC-stearic
acid films have much higher permeability when the films have been stretched slightly.
However, films thicker than 15 pm seemed not to depend on the thickness of the film,
and the
WVP
values were lower than LDPE of 0.0529
X
10-l2 g dm2 spa. They did
not test the film thickness above 37.1 pm.~artin-polo
et
al.
(1992) also noted that the
water vapor transfer rate of cellophane films coated with paraffin wax or oil decreased
when thickness increased from 30 to 60 pm, but remained almost constant up to
120 pm. Debeaufort and Voilley (1995) showed that the
WVP
decreased exponentially
when the triglyceride layer thickness increased from 0 to 60 pm, and remained con-
stant for higher thickness, although the critical value is about 300 pm in the case of
paraffin-based films.
lnfluence
of
the
RH
differentials
The driving force of the transfer of water vapor is the vapor pressure difference
between the two sides of the film. However, it is well known that the
WVP
of
hydrophilic films depends both on the relative humidity
(RH)
difference and on the
absolute humidity values.
In
hydrophilic films, the WVP is moisture-dependent
-
that
is, at high relative humidity the moisture content of the film increases and the film
becomes plasticized. Polymer chain mobility increases, thereby increasing moisture
diffusivity. Lipid-biopolymer composite films display the same behavior, but the effect
of the RH gradient is less pronounced until extremely high
RH
conditions are reached.
Figure 21.6 shows the effect of RH differentials on the
WVP
of HPMC-stearic acid
composite films. The film exhibited greater permeability as the RH differentials
increased. At 9710% RH, the WVP of the films increased to about four times its value
at 9410% RH, and at 9910% RH it again doubled.
Kester and Fennema (1989a) also observed that the permeability to water vapor of
steariclpalmitic-cellulose
ether films increased approximately five-fold as the
RH
on
the low water vapor-pressure side of the film was elevated from 0 to 65% (9710% vs
97165%). As the RH on the low humidity side of the film was increased, the equilib-
rium RH within the film matrix was elevated. The elevation of the absorbed moisture
had a plasticizing effect, which increased the diffusion of the moisture through the
film.
lnfluence
of
temperature
Temperature affects all thermodynamic and kinetic phenomena, and thus the transfer
of water vapor through films, tremendously. Permeability is defined as the product of
diffusivity and solubility coefficients, and therefore depends both on diffusion
(kinetic factor) and sorption (thermodynamic factor). Generally, an increase in tem-
perature causes an increase in diffusion due to an increase in molecular thermal motion.
In
contrast, water sorption is favored by a decrease
in
temperature. Consequently, the
376
Innovations
in
Food
Packaging
0
I
I I I I I
I
I
84 86 88 90 92 94 96 98 100
RH
differentials
Figure
21.6
Effect of RH differentials on the
WVP
of hydroxypropyl methylcellulose composite films
containing
57%
or
61%
of stearic acid (from Hagenmaier and Shaw,
1990).
permeability can either increase or decrease when temperature increases. Kamper and
Fennema (1984b) observed approximately a six-fold increase
in
WVP
through a
bi-layer film of steariclpalmitic acids-HPMC upon decrease of the temperature from
25°C to 5OC, probably due to shrinking and breaking of the film as the components
became more rigid. This also may be due to an increase in film hydration at lower tem-
peratures, thus facilitating moisture transfer through the film. Kester and Fennema
(1989a) also showed a decrease of the
WVP when the temperature decreased from
40°C to 15OC with the activation energy of 59 Wmol, but the
WVP
increased at 4OC,
which deviated from linearity obtained from higher temperatures in the Arrhenius plot
(Figure 2 1.7). They explained that the deviation at 4OC was due to the lipid contrac-
tion at lower temperatures resulting in minor defects or flaws in the
film, thereby low-
ering its resistance to water vapor resistance. Generally, wax-laminated films are not
used at low temperatures because of the tendency for waxes to become brittle under
these conditions. However, Kester and Fennema (1989a) asserted that the beeswax-
coated lipid-cellulose ether film they developed was remarkably stable against frac-
ture at low temperatures, indicating a potential utility in frozen foods.
Applications
The use of lipids in coatings has been practiced for centuries. Coating oranges and
lemons with wax dates back to the twelfi century (Hardenburg, 1967), whereas coat-
ing foods with fats to prevent moisture loss (a practice known as "larding") was used
in
England during the sixteenth century (Labuza and Contreras-Medellin, 1981).
Waxes (e.g. carnauba wax, beeswax, paraffin wax) and oils (mineral oil, vegetable oil)
Lipid-based edible films and coatings
377
Figure
21.7
Effect oftemperature on the watervapor permeabilityofa lipid-based edible film.
(Reproduced from Kester and Fennema, 1989a, with permission from the Institute of Food Technologists.)
have been used commercially since the 1930s as protective coatings for fresh fruits
and vegetables (Baldwin, 1994).
Potential applications of the lipid-based edible films and coatings include the
following.
Fresh and processed food products
Currently, lipids are used as edible films and coatings for meat, poultry, seafood, fruits,
vegetables, grains, candies, heterogeneous and complex foods, or fresh, cured, frozen,
and processed foods.
In the case of fruits and vegetables, coatings are used to prevent weight loss (retain
moisture), to slow down aerobic respiration, and to improve the appearance by pro-
viding gloss. Shellac and waxes are the most common coating agents used to improve
fruit gloss. However, fruits coated with shellac have been reported to develop a
whitening of the skin due to the condensation that develops when they are brought
from cold storage to ambient temperatures (Hagenmaier and Baker, 1994).
Hagenmaier and Baker (1996) also pointed that in some applications of fruit coatings,
like citrus fruit, candelilla and other waxes are more advantageous than shellac or
wood rosin because the former are more permeable to oxygen and carbon dioxide
than the latter (Hagenmaier and Shaw, 1992). Coatings with too high a barrier to
permanent gases can lead to fruit senescence and off-flavor production. Formulating
shellac coatings with a lipid component, such as candelilla or carnauba wax, maintains
the glossy appearance of a shellac coating but increases oxygen permeability, thereby
reducing the production of ethanol that can occur in shellac-coated apples (Alleyne
and Hagenmaier, 2000; Bai
et
al.,
2003).
378
Innovations
in
Food Packaging
Lipids and resins are useful in reducing surface abrasion during handling opera-
tions, by sealing tiny scratches that may occur on the surface of hits and vegetables
during harvest, handling and processing (Hernandez, 1994). Fruits and cleaned veg-
etables are often coated with waxes in cases where the peel will not be consumed
-
e.g. lemons, oranges, tangerines, and melons
-
or when the hit must be transported
over long distances. The colorless, odorless, and tasteless macrocrystalline slab waxes
are especially valuable. Small quantities of hard waxes such as carnauba, ouricouri or
montan waxes are incorporated to impart a gloss.
Wax and water spray emulsions have been used for apples, pears, citrus fruits, and
tomatoes. The emulsion must have low surface tension, good wetting power, and dry
rapidly after the coating process.
A
typical emulsion formulation is sodium hydroxide
(6
parts), triethanolamine (20 parts), stearic acid (42 parts), paraffin wax (1-5 parts),
carnauba (55 parts), shellac (100 parts) and water (2000 parts).
Paraffi wax is used in the poultry-processing industry for wax picking of ducks
and geese. The microcrystalline slab waxes are too brittle for this task, and blends of
macro- and microcrystalline waxes plus an additive of polyethylene waxes are used.
Cheese is also coated with a paraffin wax to prevent its desiccation and the loss of
flavor substances, and to protect the surface from undesired mold formation.
Stuchell and Krochta (1995) displayed efficient protection of frozen king salmon
against lipid oxidation and water loss by using a coating composed of a mixture of
whey proteins and acetylated monoglycerides. They reported that moisture loss was
reduced by 4245% during 3 weeks of storage at -23OC.
One of the main uses for shellac coatings is as a confectioner's glaze on candies and
panned confections. Shellac is used primarily to impart high gloss to these items, but
the hydrophobic character also serves as a barrier to recrystallization and to agglom-
eration of loose confections in high humidity.
Lipid coatings have been effective at reducing moisture uptake or loss, and mini-
mizing or delaying oxidative rancidity and moisture uptake in raisins and nuts. For
example, mixtures of various antioxidants (TBHQ, BHA, BHT) and citric acid in
hydrogenated vegetable oil or in acetylated monoglycerides have been effective at
minimizing oxidative rancidity in peanuts. Mineral oil has traditionally been used to
prevent the clumping of raisins, as well as to improve their appearance (Kochar and
Rossell, 1982). Furthermore, raisins have been stabilized against moisture loss by
coating with beeswax (Watters and Brekke, 1961).
Minimally processed
fruits
and vegetables
The growing demand for convenience has influenced the product form in which
fruits and vegetables are consumed. Pre-packaged salads, pre-cut fruits, broccoli and
cauliflower florets, stir-fiy mixes, and packaged carrot and celery sticks are examples
of value-added produce that appeal to consumers seeking health and convenience.
Minimally processed fruits and vegetables are often exposed to substantial mechan-
ical injury and wounding, inducing increased respiration, accumulation of secondary
metabolites, increased ethylene synthesis, and cellular disruption (Rolle and Chism,
1987). Maintaining the cell membrane integrity and reducing the chemical and
enzymatic reactions are major concerns in extending the shelf life of minimally
~ipid-based edible films and coatings
379
processed fruits and vegetables. The application of semi-permeable edible coatings is
promising in this field (Baldwin
et
al., 1997). Avena-Bustillos
et
al. (1994) showed
that using an edible coating of sodium caseinate-stearic acid emulsion on peeled car-
rots reduced surface dehydration and white blush formation. This is important, since
white blush on the surface is a major factor in reducing consumer acceptance of
min-
imally processed carrots.
Active packaging
Active packaging is an innovative packaging system in which the package, the prod-
uct, and the environment interact to prolong the shelf life or to enhance the safety or
sensory properties, while maintaining the quality of the product. This is particularly
important in the area of fresh and extended shelf-life foods. Floros
et
al. (1997)
reviewed active packaging and recognized antimicrobial packaging as one of the most
promising versions of an active packaging system. Recently, Han (2000) and Vermeiren
et
al. (2002) reviewed antimicrobial packaging, and Suppakul
et
al. (2003) published
a review article on active packaging with an emphasis on antimicrobial packaging.
The incorporation of preservatives into edible films and coatings to control surface
microbial growth in foods is being explored. Film composition is one of the primary
factors affecting the difisivity of preservatives in edible films (Ozdemir and Floros,
2003). In particular, lipid materials are known to have pronounced effects on such dif-
fusion processes. Red1
et
al. (1996) found that films containing lipids had lower difi-
sion coefficients than those without a lipid component. Similarly, Vojdani and Torres
(1 990) showed that the type and concentration of fatty acids used in the formulation
of polysaccharide films affected the permeability of potassium sorbate through these
films. Potassium sorbate permeation decreased. Palmitic, stearic, and arachidonic
acids were effective in decreasing the potassium sorbate permeation through MC and
HPMC films. The application of a lipid material such as beeswax in the form of a sec-
ond layer on polysaccharide films containing potassium sorbate resulted in films with
extremely low potassium sorbate permeability values (Vojdani and Torres, 1989).
Edible packaging
Edible packaging refers to the use of edible films, pouches, bags, and other containers
for packaging of food products (McHugh and Krochta, 1994~). Potential uses for edi-
ble packages include the pre-measuring of ingredients, and controlling the atrnos-
phere around fresh fruits and vegetables. When the consumption of the final package
is not desirable, such as for short-term storage of foods using wraps or bags, edible
packages could quickly be composted using domestic or municipal facilities. Edible
packages offer environmental advantages, as well
as
cost and convenience advantages,
over conventional synthetic packaging systems. Lipid-based edible films can be used
where traditional plastic packaging materials cannot be applied
-
that is, they can sep-
arate and reduce migration of moisture in multi-component foods. Kamper and
Fennema (1 985) used a bi-layer film consisting of lipid and a layer of HPMC between
tomato-paste ground crackers. The film substantially slowed the transfer of water
from the salted tomato paste to the crackers.
380
Innovations in
Food
Packaging
Another major potential use of lipid-based edible films composed with hydrocol-
loids (e.g. starch) is as bags for fresh fruits, vegetables, and bread. Though the size of
this market is still very limited as a result of the price difference in comparison with
traditionally used synthetic plastics, the advantages of these films (selective perme-
ability, biodegradability, and maintenance of the high quality of foods) may ultimately
drive their commercial acceptance.
Conclusions
Edible films and coatings have shown potential for controlling the transfer of moisture,
oxygen, lipids, aroma and flavor compounds in food systems, with a resulting increase
in food quality and shelf life, while reducing the use of synthetic plastic packaging
materials. Many materials have been used for film and coating formulations, such as
carbohydrates, proteins, lipids, and mixtures of these. Due to the hydrophilic nature of
most biopolymers, achieving adequate moisture barriers requires the formation of
composite films that contain hydrophobic materials such as edible fatty acids or waxes.
Two primary preparation systems exist for lipid-based edible films; emulsion films
and bi-layer films. Pure lipid coatings are used in most cases, while freestanding lipid
films cannot be manufactured due to their low mechanical strength. Film properties
such as barrier, mechanical, thermal, and optical properties all vary depending on the
film
formulation and preparation methods, and on other external conditions such as
RH
differentials across the film, the temperature, and the packaging methods used.
The specific functional properties of lipid-based edible films and coatings can be
exploited for many foods, agricultural, pharmaceutical, and medical applications.
Indeed, lipid-based edible films and coatings will continue to play an important role
in the food industry by extending the shelf life or improving the quality of many prod-
ucts, and in some cases alleviating environmental packaging-related concerns.
References
Alleyne,
K
and Hagenmaier,
R.
D. (2000). Candelilla-shellac: an alternative formulation
for coating apples.
HortSci.
35(4), 691-693.
Avena-Bustillos,
R.
J. and Krochta, J. M. (1993). Water vapor permeability of caseinate-
based edible films as affected by pH, calcium crosslinking and lipid content.
.I
Food
Sci.
58,904-907.
Avena-Bustillos, R. J., Krochta, J. M., Saltveit,
M.
E., Rojas-Villegas,
R.
J.
and Sauceda-
Pbrez, J. A. (1994). Optimization of edible coating formulations on zucchini to
reduce water loss.
J
Food Eng.
21,
197-214.
Bai, J., Hagenmaier, R.
D.
and Baldwin, E.
A.
(2003). Coating selection for 'Delicious'
and other apples.
Postharvest Biol. Technol.
28(3), 381-390.
Baldwin,
E.
A.
(1994). Edible coatings for hits and vegetables, past, present and future.
In:
Edible Coatings and Films to Improve Food Quality
(J.
M.
Krochta,
E.
A. Baldwin
and M. Nisperos-Carriedo, eds), pp. 25-64. Technomic Publishing Company, Inc.,
Lancaster, PA.
Baldwin,
E.
A., Nisperos-Carriedo, M.
O.,
Hagenmaier,
R.
D. and Baker, R. A. (1997).
Use of lipids in coatings for food products.
Food Technol.
51(6),
56-64.
Lipid-based edible
films
and coatings
381
Banerjee, R. and Chen, H. (1997). Functional properties of edible films using whey pro-
tein concentrate.
J;
Dairy Sci.
78, 1673-1683.
Banker, G. S. (1966). Film coating theory and practice.
J;
Pharm. Sci.
55,81-89.
Cuq, B., Gontard, N. and Guilbert, S. (1995). Edible films and coatings as active layers. In:
Active Food Packaging
(M.
L.
Rooney, ed.), pp. 112-142. Chapman and Hall,
London, UK.
Debeaufort, F. andvoilley, A. (1995). Effect of surfactants and drying rate on barrier prop-
erties of emulsified edible films.
Int.
J;
Food Sci. Technol.
30, 183-190.
Debeaufort, F., Martin-Polo, M. and Voilley, A. (1 993). Polarity homogeneity and structure
affect water vapor permeability of model edible films.
J;
Food Sci.
58,426-429,434.
Debeaufort, F., Quezada-Gallo, J. A. and Voilley, A. (1998). Edible films and coatings:
Tomorrow's packagings: a review.
Crit.
Rev.
Food Sci.
38,299-3 13.
Fairley,
P.,
Krochta,
J.
M.
and German, J. B. (1997). Interfacial interactions in edible emul-
sion films from whey protein isolate.
Food Hydrocolloids
11,245-252.
Floros,
J.
D., Dock,
L. L.
and Han, J.
H.
(1997). Active packaging technologies and appli-
cations.
Food Cosmet. Drug Packag.
20(1), 10-17.
Gennadios, A., Weller, C. L. and Testin, R. F. (1993). Modification of physical and barrier
properties of edible wheat gluten-based films.
Cereal Chem.
70(4), 426429.
Gennadios, A., McHugh, T. H., Weller, C.
L.
and Krochta,
J.
M. (1994). Edible coatings and
films based on proteins.
In:
Edible Coatings and Films to Improve Food Quality
(J.
M.
Krochta, E. A. Baldwin and M. Nisperos-Carriedo, eds), pp. 201-277.
Technomic Publishing Co., Inc., Lancaster, PA.
Gontard, N., Duchez, C., Cuq,
J.
L.
and Guilbert,
S.
(1994). Edible composite films of
wheat gluten and lipids: Water vapor permeability and other physical properties.
Intl.
J;
Food Sci. Technol.
29,39-50.
Gontard, N., Marchesseau, S., Cuq, J. L. and Guilbert, S. (1995) Water vapor permeabil-
ity of edible bilayer films of gluten and lipids.
Intl.
J;
Food Sci. Technol.
30,49-56.
Greener,
I.
K.
and Fennerna,
0.
(1989a). Barrier properties and surface characteristics of
edible bilayer films.
J;
Food Sci.
54, 1393-1399.
Greener, I.
K. and Fennema,
0.
(198913). Evaluation of edible, bilayer films for use as
moisture barriers for food.
J;
Food Sci.
54, 1400-1406.
Greener,
I.
K.
and Fennema,
0.
(1992). Lipid-based edible films and coatings.
Lipid Tech.
4,3638.
Griffin,
W. C. (1995). Emulsions. In:
Kirk-Othmer Encyclopedia of Chemical Technology,
3rd edn. Vol. 8, pp. 9 13-9 16. Wiley Interscience, New York, NY.
Guilbert,
S.
(1986). Technology and application of edible protective films.
In:
Food
Packaging and Preservation: Theory and Practice.
(M.
Mathlouthi, ed.), pp. 371-394.
Elsevier Applied Science Publishing Co., London,
UK.
Guilbert, S., Gontard, N. and Gorris, L. G.
M.
(1996). Prolongation of the shelf-life of
perishable food products using biodegradable films and coatings.
Lebensm.-JRss.
Technol.
29,10-17.
Hagenmaier, R.
D. and Shaw, P. E. (1990). Moisture permeability of edible films made
with fatty acid and (hydroxypropyl) methylcellulose.
J
Agric. Food Chem.
38,
1799-1803.
Hagenmaier,
R.
D. and Shaw, P. E. (1992). Gas permeability of fruit coating waxes.
J
Am.
SOC. Hort. Sci.
117, 105-109.
382
Innovations
in
Food
Packaging
Hagenmaier, R. D. and Baker, R. A. (1994). Wax microemulsions and emulsions as citrus
coatings.
.l
Agric. Food Chem.
42,899-902.
Hagenmaier, R. D. and Baker, R. A. (1995). Layered coatings to control weight loss and
preserve gloss of citrus fruit.
HortSci.
30,296298.
Hagenmaier, R. D. and Baker, R. A. (1996). Edible coatings from candelilla wax
microemulsions.
J
Food Sci.
61,562-565.
Hamilton, R. J. (1995). Commercial waxes: Their composition and applications. In:
Waes:
Chemistry, Molecular Biology and Functions
(R. J. Hamilton, ed.), pp. 257-309. The
Oily Press, Dundee,
UK.
Han, J. H. (2000). Antimicrobial food packaging.
Food Technol.
54(3), 56-65.
Hardenburg, R. E. (1967). Wax and related coatings for horticultural products.
A
bibliog-
raphy.
Agric. Res. Service Bull.
pp. 51-55. USDA, Washington, DC.
Hernandez,
E.
(1994). Edible Coatings from Lipids and Resins. In:
Edible Coatings and
Films to Improve Food Quality
(J.M. Krochta, E.A. Baldwin and M. Nisperos-
Carriedo, eds), pp. 279-303. Technomic Publishing Company, Inc., Lancaster, PA.
Kamper,
S.
L. and Fennema, 0. (1984a). Water vapor permeability of edible bilayer films.
.l
Food Sci.
49,1478-1481,1485.
Kamper, S. L. and Fennema, 0. (1984b). Water vapor permeability of an edible, fatty acid
bilayer film.
.l
Food Sci.
49, 1482-1485.
Kamper, S. L. and Fennema, 0. (1985). Use of an edible film to maintain water vapor gra-
dient in foods.
.l
Food Sci.
50,382-284.
Kester, J. J. and Fennema, 0. (1986). Edible films and coatings: A review.
Food Technol.
40(12), 47-59.
Kester, J. J. and Fennerna,
0.
(1989a). An edible
film
of lipids and cellulose ethers: Barrier prop-
erties to moisture vapor transmission and structud evaluation.
J
FoodSci.
54,1383-1389.
Kester, J. J. and Fennema,
0.
(1989b).
An
edible film of lipids and cellulose ethers:
Performance in a model frozen-food system.
J
Food Sci.
54,1390-1 192,1406.
Kochhar,
S.
P.
and Rossell, J. B. (1982). A vegetable oiling agent for dried fruits.
.l
Food
Technol.
17,661.
Koelsch, C.
M.
(1994). Edible water vapor barriers: properties and promise.
Trends Food
Sci. Technol.
5,768 1.
Koelsch, C. M. and Labuza, T.
P.
(1992). Functional, physical and morphological proper-
ties of methyl cellulose and fatty acid-based edible barriers.
Lebensm. Wiss. Technol.
25,404-4 1 1.
Krochta, J. M. and De Mulder-Johnston, C. (1997). Edible and biodegradable polymer
films: Challenges and opportunities.
Food Technol.
51(2), 61-74.
Labuza, T. P. and Contreras-Madellin, R. (1981). Prediction of moisture protection
requirements for foods.
Cereal Foods World
26,335-343.
Martin, J. (1982). Shellac. In:
Kirk-Othmer Encyclopedia of Chemical Technology,
pp. 737-747. Wiley Interscience, New York,
NY.
Martin-Polo, M., Mauguin, C. and Voilley, A. (1992). Hydrophbic films and their efficiency
against moisture transfer. 1. Influence of the film preparation technique.
.l
Agric.
Food Chem.
40,407412.
McHugh, T. H., Avena-Bustillos, R. and Krochta, J. M. (1993). Hydrophilic edible films:
Modified procedure for water vapor permeability and explanation of thickness
effects.
.l
Food Sci.
58, 899-903.
Lipid-based edible films and coatings
383
McHugh, T. H. and Krochta, J. M. (1994a). Water vapor permeability properties of edible
protein-lipid emulsion films.
J
Am. Oil. Chem. Soc.
71,307-312.
McHugh, T. H. and Krochta, J. M. (1994b). Dispersed phase particle size effects on water
vapor permeability of whey protein-beeswax edible emulsion films.
J
Food Process.
Presew.
18,173-188.
McHugh, T. H. and Krochta, J. M. (1994~). Milk protein based edible films and coatings.
Food Technol.
48(1), 97-1 03.
Morillon,
X,
Debeaufort, F., Blond, G., Capelle, M. andvoilley,
A.
(2002). Factors affect-
ing the moisture permeability of lipid-based edible films:
A
review.
Crit.
Rev.
Food
Sci.
Nutr.
42,67-89.
Ozdemir, M. and Floros, J.
D.
(2003). Film composition effects on diffusion of potassium
sorbate through whey protein films.
J
Food Sci.
68,511-5 16.
Park, J. W., Testin, R.
E,
Park, H. J., Vergano,
P.
J. and Weller, C.
L.
(1994). Fatty acid con-
centration effect on tensile strength, elongation and water vapor permeability of lam-
inated edible films.
J
Food Sci.
59,9 16-9 19.
Pkrez-Gago, M. B. and Kcrochta, J. M. (1999). Water vapor permeability of whey protein
emulsion films as affected by pH.
J
Food Sci.
64,695-698.
Redl, A., Gontard,
N.
and Guilbert, S. (1996). Determination of sorbic acid diffusivity in
edible wheat gluten and lipid based films.
1
Food Sci.
61, 116-120.
Rhim, J. W., Wu, Y., Weller,
C.
L. and Schnepf, M. (1999). Physical characteristics of
emulsified soy protein-fatty acid composite films.
Sci. Alimentas
19,57-71.
Rolle, R. S. and Chism, G. W. 111. (1987) Physiological consequences of minimally
processed hits and vegetables.
J
Food Quality
10, 157-177.
Shellhammer, T. H. and Krochta, J. M. (1997). Whey protein emulsion film performance
as affected by lipid type and amount.
J
Food Sci.
62,390-394.
Stuchell, Y. M. and Krochta, J. M. (1995). Edible coatings on frozen king salmon: effect
of whey protein isolate and acetylated monoglycerides on moisture loss and lipid oxi-
dation.
J
Food Sci.
60,28-3 1.
Suppakul,
P.,
Miltz, J., Sonneveld, K. and Bigger, S. W. (2003).
J
Food Sci.
68,408-420.
Tanaka, M., Ishizaki, S., Suzuki, T. and Takai, R. (2001). Water vapor permeability of edi-
ble films prepared from fish water soluble proteins as affected by lipid type.
J
Tokyo
Univ. Fisher.
87,3 1-37.
Vermeiren, L., Devlieghere,
E
and Debvere, J. (2002). Effectiveness of some recent
antimicrobial packaging concepts.
Food Add. Contam.
19(suppl.), 163-1 7 1.
Vojdani, F. and Torres,
J. A.
(1989). Potassium sorbate permeability of edible cellulose
ether films.
J
Food Process. Presew.
13,417430.
Vojdani, F. and Torres, J.
A.
(1990). Potassium sorbates permeability of methylcellulose and
hydroxypropyl methylcellulose coatings: Effect of fatty acids.
J
Food Sci.
55,841-846.
Watters, G. G. and Brekke, J. E. (1961). Stabilized raisins for
dry
cereal products.
Food
Technol.
5,236-238.
Weller, C. L., Gennadios, A. and Saravia, R. A. (1998). Edible bilayer films from zein and
grain sorghum wax or carnauba wax.
Lebensm. -Wiss. u. -Technol.
31,279-285.
Wong, D. W. S., Tillin, S. J., Hudson, J. S. and Pavlath,
A.
E. (1994). Gas exchange in cut
apples with bilayer coatings.
J
Agric. Food Chem.
42,2278-2285.
Emulsion
and bi-layer
edible
films
Maria
B.
Perez-Gago
and
John
M.
Krochta
Introduction
...........
Composite film formation
.
.
Properties of bi-layer films .....
Properties of emulsion films
....
Conclusions
................
References ..............
Introduction
An
edible film is defined as a thin layer of edible material, either formed on a food as
a coating, or preformed and then wrapped around a food or placed between food com-
ponents (Krochta, 1997a). The ability to provide a barrier to moisture, oxygen, carbon
dioxide, oil, and flavor/aroma migration between adjacent food components, andlor
between the food and the environment, is the reason for the great interest in edible
films in recent years (Guilbert, 1986; Kester and Fennema, 1986; Krochta, 1992).
The barrier characteristics of edible films can also enable a reduction and simplifica-
tion of the packaging material required for a food product. Additional benefits are
the improvement of the mechanical integrity or handling characteristics of the food,
and functionality by incorporating food ingredients such as antioxidants, antimicro-
bials, or flavors.
Development of edible films has been mainly focused upon barriers containing pro-
teins, polysaccharides, or lipids. The functional properties of the resulting film depend
on the nature of the film-forming material.
In
general, polysaccharides and proteins,
which are polymeric and hydrophilic by nature, are good film-formers and excellent
oxygen, aroma, and lipid barriers at low relative humidity. However, they are poor
moisture barriers compared to synthetic moisture-barrier films such as low-
density polyethylene (LDPE) (Table 22.1). Lipids, which are hydrophobic, are better
moisture barriers than polysaccharides and proteins, and are comparable to synthetic
films (Table 22.1). However, their non-polymeric nature limits their ability to form
cohesive films.
In
addition, some lipids require solvents or
high
temperatures for casting
Innovations in Food Packaging
ISBN:
0-12-31 1632-5
Copyright
O
2005
Elsevier
Ltd
All rights of reproduction in
any
form resewed