improved in food pakaging with biobased nanocomposites
TRANSCRIPT
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International Journal of Food
Engineering
Volume3, Issue4 2007 Article3
Improvement in Food Packaging Industry with
Biobased Nanocomposites
Zahra Akbari Talat Ghomashchi
Shahin Moghadam
Chemical Engineering Faculty, Amirkabir University, Tehran, Iran, [email protected] Engineering Department, Faculty of Engineering, Tehran University, Tehran, Iran,
[email protected] of Chemistry, Tarbiat Moallem University, Tehran, Iran, sh [email protected]
Copyright c2007 The Berkeley Electronic Press. All rights reserved.
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Improvement in Food Packaging Industry with
Biobased Nanocomposites
Zahra Akbari, Talat Ghomashchi, and Shahin Moghadam
Abstract
Nanotechnology will become one of the most powerful forces for innovation in the food pack-
aging industry. One such innovation is biobased nanocomposite technology, which holds the key
to future advances in flexible packaging. Biobased nanocomposites are produced from incorpora-
tion of nanoclay into biopolymers (or Edible films). Advantages of biobased nanocomposites are
numerous and possibilities for application in the packaging industry are endless. A comprehensive
review of biobased nanocomposite applications in food packaging industry should be necessary
because nanotechnology is changing rapidly and the food packaging industry is facing new chal-
lenges. This provides a general review of previous works. Many of the works reported in the
literature are focused on the production and the mechanical properties of the biobased nanocom-
posites. Little attention has been paid to gas permeability of biobased nanocomposites. In regard
to extensive research on Edible film, this article suggests investigating the replacement of biobased
nanocomposites instead of Edible films in different areas of food packaging.
KEYWORDS:nanotechnology, food packaging, nanocomposite, permeability, edible film
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1. INTRODUCTIONBiobased nanocomposites are a new class of materials in food packaging
industry with improved barrier and mechanical properties as compared tothose of neat biopolymers. They are biodegradable and they are also produced
from renewable resources. So, these make them environment friendly. It
should be noted that barrier properties and especially mechanical properties of
biobased nanocomposite films are stronger than Edible films and synthetic
polymeric films. Unlike Edible films, they could not have been consumed as a
part of food.
Biobased nanocomposites can be used to extend the shelf-life of the
fresh products such as fruits and vegetables by controlling of respiratory
exchange. Also it can improve the quality of fresh, frozen, and processed
meat, poultry, and seafood products by retarding moisture loss, reducing lipid
oxidation and discoloration, enhancing product appearance, and reducing oil
uptake by battered and breaded products during frying.Biobased nanocomposite is interface between two important subjects
in food packaging industry, namely Edible films and nanocomposites.
Therefore, this paper starts with short explanations about Edible films and
nanocomposites. Furthermore, a literature review about biobased
nanocomposites is presented. The last objective of this review is to explain a
procedure for the replacement of biobased nanocomposites instead of Edible
films in food packaging industry.
2. EDIBLE FILMSEdible films are defined as a thin layer of edible material formed on food as a
coating. Additionally, Edible films can carry antioxidants (Han, 2001) andantimicrobials (Pena and Torres, 1991), while traditional packaging materials
can not compete in these aspects. Edible films are used to extend the shelf life
of food and maintain its quality by inhibiting the migration of moisture,
oxygen, carbon dioxide, aromas and lipids (Quintavalla and Vicini, 2002).
Other favorable aspects of Edible films are: completely biodegradable
(Guilbert et al., 1996; Arvanitoyannis et al., 1996) can be a part of a food and
can reduce the consumption of naphtha-based polymeric films (Parra et al.,
2004). The properties of the edible films which have been mostly evaluated
are mechanical properties and specially gas permeability properties
(Robertson, 1993).
A major component of Edible films is the plasticizer. The addition of a
plasticizer agent to Edible films is required to overcome film brittleness,caused by high intermolecular forces. Plasticizers reduce these forces and
increase the mobility of polymer chains, thereby improving flexibility and
extensibility of the film. On the other hand, plasticizers generally decrease gas,
water vapor and solute permeability of the film and can decrease elasticity and
cohesion (Parra et al., 2004).
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Type of degradation reactions in food systems determines optimum
gases composition in food packaging. For example, oxygen is involved in
many degradation reactions in foods, such as fat and oil rancidity,
microorganism growth, enzymatic browning and vitamin loss. Thus, manypackaging strategies seek to exclude oxygen in packaging to protect the food
product (Gontard et al., 1996). On the other hand, the permeability of Edible
film to oxygen and carbon dioxide is essential for respiration in living tissues
such as fresh fruits and vegetables. So, moderate barrier materials are more
appropriate. If an Edible film with the appropriate permeability is chosen, a
controlled respiratory exchange can be established and thus the preservation of
fresh fruits and vegetables can be prolonged. So the main characteristics to
consider in the selection of Edible film are their oxygen, carbon dioxide and
water vapor permeability (Ayranci and Tunc, 2002). The success of Edible
films for fresh products totally depends on the control of internal gas
composition (Park, 1999). Semi-permeable coatings can create a modified
atmosphere (MA) (Nisperos, 1990; Baldwin 1994) similar to controlledatmosphere (CA) storage, with less expense incurred. However, the
atmosphere created by coatings can change in response to environmental
conditions, such as temperature and humidity, due to combined effects on fruit
respiration and coating permeability (Baldwin 1994; McHugh and Krochta,
1995). Types of deteriorative reactions, required gas composition and some
case study have been summarized in Table 1 for important areas of food
industry.
Edible films have been prepared by casting solutions of proteins,
carbohydrates and lipids, in different combinations and compositions (Kester
and Fennema, 1986; Krochta, 1992). Edible films which are made of proteins
are most attractive. Firstly, they are supposed to provide nutritional value
(Gontard, and Guilbert, 1994). Secondly, protein-based films have impressivegas barrier properties compared with those from lipids and polysaccharides.
For example, oxygen permeability of soy protein-based films (when they are
not moist) was 500, 260, 540 and 670 times lower than that of low-density
polyethylene, methylcellulose, starch and pectin, respectively. On the other
hand, their mechanical properties are also better than those of polysaccharide
and fat based films because proteins have a specific structure which confers a
wider range of functional properties, especially high intermolecular binding
potential. In addition, Proteins, such as casein, whey proteins and corn zein,
have also been used in Edible film formulation as a moisture barrier since
these proteins are abundant, cheap and readily available. Therefore,
incorporation of nanoclay in Edible films, especially protein based, can greatly
improve their properties.
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Table 1. Basic information for design of edible packaging in different foods
with some case study
Types of Edible filmRequired gas
composition
Degradation
reaction
Food
Mango(Polysaccharide)
apple (whey,CMC),
Cherry, Kiwi (CMC,
soy protein),
strawberry
(Polysaccharide),
Avacado(CMC),Apricot (MC)
Carrot (starch),
Mushroom(MC), green
pepper and cauliflower
(MC),
Meat(corn zein, casein)
pork(starch/alginate)
poultry(corn zein, agar
casein), chicken(CMC)
fish (carrageenan)
lipids
Oxygen (1-5%)
CO2 (0-5%)
Oxygen (1-5%)
No CO2
Oxygen (70-
80%), CO2
(30-20%)
Low oxygen,
High CO2
CO2 (40%),
Oxygen (30%)
CO2 (40-60%),
Nitrogen
(60-40%)
------
High respiration
rate, water loss,
Microbial growth
High respiration
rate, water
loss, Microbial
growth
Photooxidation of
the pigment,
Microbial growth
Photooxidation of
the pigment,
Microbial growth
Autolysis caused
by intrinsic
enzymes,
metabolic activity
of microorganisms,
and oxidation
Bacteria growth
Fruits
Vegetables
Meat
Red meat
Other meat
Fish
low fat
high fat
Egg
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Rice (Ethyl cellulose,
pectin)
Frozen salmon (whey),
Beef (colagen), meat
(hydroxypropylated
high amylose starch),
frozen strawberries
(chitosan)
Fried potato (hydroxyl
propyl methylcellulose),
Starchy product(corn
zein), cereal (gelatine,
gellan gum, and
carrageenan)
Low oxygen
Low oxygen
Low oxygen
Fungal growth,
staling, and
moisture absorption
/ desorption
Degradation of
pigments and
vitamins, oxidation
of lipids, and
destabilization of
proteins.
Oxidative reaction
Bread
Frozen food
Fried foods
3. NANOCOMPOSITESThe large industrial demand for polymers has lead to an equally large interest
in polymer composites to enhance their properties. Clay-polymer
nanocomposites are among the most successful nanotechnological materialstoday. This is because they can simultaneously improve material properties
without significant trade-offs. Nanocomposites are polymer systems
containing inorganic particles with at least one dimension in the nanometer
range (Gilmer et al., 2002). Because the nanoparticles are so small and their
aspect ratios (largest dimension/smallest dimension) are very high, even at
such low loadings, certain polymer properties can be greatly improved without
the detrimental impact on density, transparency, and processability associated
with conventional reinforcements like talc or glass (Lei et al., 2006). Nano-
sized particles are carbon black, fumed silicate, nano-oxides, carbon nanotubes
and nanoclays. Nanotube-based nanocomposites are used for electrostatic
dissipation applications; nanoscale oxides and metals are used for abrasion-
resistant films; and nanoclay-based nanocomposites are used for barrier
packaging applications (Scott and Wood, 2003). Some of the improved
properties of nanoconposite are:
Improved durability due to increased strength (Angles and Dufresne, 2001;
Wang et al., 2003)
Better barrier properties, e.g. for packaging (Alexandra and Dubois, 2000)
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Better optical properties due to extremely small size of nanoparticles (Wan et
al., 2003)
Easier processing due to lower viscosity (Schartel et al., 2005)
Good recycling properties (McGlashan and Halley, 2003)Preparations methods of nanocomposite are solution included
intercalation, in-situ Polymerization and melt processing. Melt processing is
done simultaneously when the polymer is being processed through an
extruder, injection molder, or other processing machine. The polymer pellets
and clay are pressed together using shear forces to help with exfoliation and
dispersion. With in-situ polymerization, clay is added directly to the liquid
monomer during the polymerization stage. In the last method, clay is added to
a polymer solution using solvents to integrate the polymer and clay molecules.
3.1. NANOCOMPOSITE PERMEABILITY
Many factors should be taken into consideration in designing food packaging.One of the very important factors is gas permeability. Gases have different
permeability which is determined by gas molecule dimension (dynamic
diameter) and gas molecule shape. Nitrogen has the smallest permeability rate;
oxygen has bigger while carbon dioxide has the biggest. The gas permeation
can be described mathematically by Fick's first law. The flux (J), the net
amount of gas that diffuses through unit area per unit time, which is
proportional to the concentration gradient can be defined in one direction as
follows (Park, 1999):
X
CDJ
= .
(1)
Where, J is the flux (sm
gr
.2or
sm
ml
.2), D is the diffusivity coefficient (
s
m2
), C
is the concentration gradient of the gas and X is the thickness of the neat
polymeric film (m) (Crank, 1975; Jost 1960; Landrock and Proctor, 1952;
Chang, 1981). With the two assumptions, (1) the diffusion is in steady state
and (2) there is a linear gradient through the film, the flux (J) is given by:
tA
Q
X
CCDJ
.. 12 =
=
(2)
Where, Q is the amount of gas diffusing through the film (g or ml), A is area
of the film (m2) and t is the time (s). After application of Henry's law, the
driving force is expressed in terms of partial pressure differential of gas and a
rearrangement of terms yields the following equation in terms of permeability.
( )X
PP
X
PPSD
tA
Q =
=
..
.
12 (3)
Where, S is the Henry's law solubility coefficient (mole/atm), p is partial
pressure difference of the gas across the film (Pa) and P is the permeability of
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neat polymeric film ((ml or g) m/m2.s.Pa). Then, the permabilities of O2, CO2
and H2O vapor can be calculated from the following equation:
PtA
XQp
=
..
.
(4)
The gaseous barrier property improvement that can result from incorporation
of relatively small quantities of nanoclay materials is shown to be substantial.
Further data reveals the extent to which both the amount of clay incorporated
in the polymer (Thomassinet al., 2006; Kim et al., 2005) and the aspect ratio
of the filler (Xu et al., 2006) contributes to overall barrier performance.
As mentioned above, Nanocomposites are constructed by dispersing a
filler material into nanoparticles that form flat platelets. Different types of
fillers are utilized; the most common is montmorillonite, layered smectite clay.
These platelets are then distributed into a polymer matrix creating multiple
parallel layers which force gases to flow through the polymer in a torturous
path, forming complex barriers to gases and water vapor. As more tortuosity is
present in a polymer structure, higher barrier properties will result (Figure 1).
Figure1.Definition of the tortuosity factor
Simple models (Yano et al., 1993; Liu et al., 2003) have been developed to
predict the gas permeability through a polymer matrix in the presence of sheet-
shaped barriers such as nanoclays, which obstruct the passage of permeant
through the matrix. Several important parameters were considered, including
the volume fraction of nanocaly ( ) and the aspect ratio of the barrier (L/W),
with higher aspect ratios providing greater barrier improvement according to
the following equation (Kim et al., 2005):
1
1 ( / 2 )
P
p L W=
+
(5)
Where P and p are the permeability coefficients of the nanocomposite and the
neat polymer, respectively. The term'
1 ( / 2 )d
L Wd
= = + is called the
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tortuosity factor (Yano et al., 1993). L and W are length and thickness of the
silicate layers respectively.
The permeability coefficient of nanocomposite films is determined
using two factors: diffusion and solubility coefficients. Effectively, morediffusion of nanoparticles throughout a polymer significantly reduces its
permeability. The degree of dispersion of the nanoparticles within the polymer
relates to improvement in mechanical and barrier properties in the resulting
nanocomposite films over those of polymer films.
Such excellent barrier characteristics have resulted in considerable
interest in nanoclay composites in food packaging applications, both flexible
and rigid. Specific examples include packaging for processed meats, cheese,
confectionery, cereals and boil-in-the-bag foods.
4. BIOBASED NANOCOMPOSITE FILMBiobased nanocomposites are composed of biopolymer, nanoclay and usuallycompatibilizing agents. Major component of biobased nanocomposites is
biopolymers. Biopolymers have great commercial potential for bioplastic and
Edible films, but some of the properties such as brittleness, low heat distortion
temperature; high gas permeability and low melt viscosity for further
processing restrict their use in a wide range of applications (Sinha and
Bousmina et al., 2005). As mentioned before, modification of biopolymers
with nanotechnology is an effective way to improve their properties.
Biopolymers derived from renewable resources are broadly classified
according to method of production. This gives the following three main
categories (Petersen et al., 1997):
1. Biopolymers directly extracted/removed from natural materials (mainly
plants) such as hydrocolloids (polysaccharides and proteins). The mostfrequently utilized polysaccharides were cellulose and starch (and their
derivatives), chitosan, seaweed extracts (carrageenans and alginates), exudate
(arabic gum), seed (guar gum), xanthan and gellan gum and pectin. Proteins
include collagen, gelatin, casein, whey proteins, corn zein, wheat gluten and
soy proteins.
2. Biopolymers produced by classical chemical synthesis from renewable
bioderived monomers like polylactate (PLA).
3. Biopolymers produced by microorganisms or genetically transformed
bacteria like Polyhydroxyalkanoates.
Hence, biopolymers which can be used in biobased nanocomposites
formulation are numerous.
The utilization of special compatibilizing agents (modifier) betweenthe two basic materials (biopolymer and nanoclay) for the preparation of
biobased nanocomposite is necessary. Layered silicates are characterized by a
periodic stacking of mineral sheets with a weak interaction between the layers
and a strong interaction within the layer. The space in-between the layers is
occupied by cations. By cation exchange reactions between the clay and
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organic cations (such as alkyl ammonium salts), the layered silicate can be
transformed into organically modified clay. The inter-layer distance will
increase by using voluminous modifiers. If this modifier is compatible with
biopolymer as well, a homogeneously and nanoscaled distribution(exfoliation) of the clay sheets can be effected in the polymer matrix. The pure
clay shows an interlayer distance of 1.26 nm. It has been proven by XRD
analysis that most of the layers are indeed swollen after the modification
reaction. The inter-layer distance changes to 2.34 nm, an increase of nearly
100% compared to the pure clay.
A comprehensive review of biobased nanocomposite film applications
in food packaging industry is necessary. Therefore, continuing this section,
several studies which are concentrated on biobased nanocomposites have been
presented.
Avella (2005) investigated on mechanical properties of biodegradable
starch/clay nanocomposite films for food packaging applications. Starch is
composed of a mixture of two substances, an essentially linear polysaccharide-amylose and a highly branched polysaccharide-amylopectin. Both forms of
starch are polymers of a-D-Glucose. Starch/clay nanocomposite films were
obtained by homogeneously dispersing montmorillonite nanoparticles in
different starch-based materials via polymer melt processing techniques. The
results show that in the case of starch/clay material, a good intercalation of the
polymeric phase into clay interlayer galleries, together with an increase of
mechanical parameters, such as modulus and tensile strength.
Biopolymers like starch present some drawbacks, such as the strong
hydrophilic behavior (poor moisture barrier) and poorer mechanical properties
than the conventional non-biodegradable plastic films used in the food
packaging industries (McGlashan and Halley, 2003; Park et al., 2003; Park et
al., 2002). So, Incorporation of nanoclay in biopolymers like starch canimprove its properties such as barrier and mechanical properties (Vaia, 2000).
The most commonly used nanoclays include montmorillonite, a 2:1
phyllosilicate (Chiou et al., 2005).
Kampeerapappun et al (2006) investigated on preparation of cassava
starch/ montmorillonite composite film. Cassava is an abundant and cheap
agricultural source of starch. This research was focused on the exploitation of
chitosan as a compatibilising agent in order to homogeneously disperse the
clay particles in a starch matrix. Mixtures of cassava starch, montmorillonite
(MMT), chitosan, glycerol as a plasticizer, and distilled water adjusted to pH 3
by acetic acid addition was well mixed with a homogenizer and gelatinized by
heating to temperatures of 7080 C. The obtained homogeneous starch
solution was cast onto an acrylic mold and allowed to dry in open air. Thepreparation of starch/montmorillonite composite film also achieved an
improvement in the physical properties including reduced surface wettability,
a decrease in water vapor transmission rate (WVTR) and moisture absorption.
The WVTR value of the biobased nanocomposite film is decreased from 2000
g m-2
day-1
(0 % wt MMT) to 1082 g m-2
day-1
(10 % wt MMT). At a fixed
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amount of MMT (10 wt%), the moisture absorption values decrease
significantly from 125% to 95%, 83%, 74%, and 61% with respect to the
chitosan contents of 0, 5, 10, 15, and 20 wt%, respectively.
Chiou et al (2005) has examined the effects of incorporating variousmontmorillonite nanoclays into starch by rheology. The nanoclays included
the hydrophilic Cloisite NaC clay as well as the more hydrophobic Cloisite
30B, 10A, and 15A clays. Frequency sweep and creep results for wheat
starchnanoclay samples at room temperature indicated that the Cloisite NaC
samples formed more gel-like materials than the other nanoclay samples.
When the various wheat starchnanoclay samples were heated to 95 0C, the
Cloisite NaC samples exhibited a large increase in modulus. In contrast, the
more hydrophobic nanoclay samples had comparable modulus values to the
neat starch sample. One of the major problems with granular starch
composites is their limited processability, due to the large particle sizes (5100
lm). Therefore, it is very difficult to make blown thin films of starch for
packing applications. For this reason, thermo plastic starch (TPS) has beendeveloped by gelatinizing granular starch with 610 wt% moisture in the
presence of heat and pressure (Sinha and Bousmina, 2005).
Park et al (2003) has shown that the tensile strength of TPS was
increased from 2.6 to 3.3 MPa with the presence of 5 wt% sodium
montmorillonite, while the elongation at break was increased from 47 to 57%.
Also the relative water vapor diffusion coefficient of TPS was decreased to
65% and the temperature at which the composite lost 50% mass was increased
from 305 to 336 0C.
Huang et al (2006) investigated on preparation of high mechanical
performance MMT urea and formamide-plasticized thermoplastic cornstarch
(UFTPCS) biodegradable nanocomposites. It was revealed that UFTPCS were
intercalated into the layers of MMT successfully, and layers of MMT werefully exfoliated and so formed the exfoliated nanocomposites with MMT. This
manufacturing process is simple and environmentally friendly.
Song et al (2006) studied compressive properties of epoxidized
soybean oil/clay nanocomposites by. Strain-rate and nanoclay weight effects
on the compressive properties of the nanocomposites were experimentally
determined. A phenomenological strain-rate-dependent material model was
presented to describe the stressstrain response. The model agrees well with
the experimental data at both large and small strains as well as high and low
strains rates.
Zengshe et al (2005) prepared epoxidized soybean oil (ESO)/clay
nanocomposites with triethylenetetramine (TETA) as a curing agent. Results
have shown that the ESO/clay nanocomposites are thermally stable attemperatures lower than 180 C, with the maximum weight loss rate after
325 C. The nanocomposites with 510 wt% clay content possess storage
modulus ranging from 2.0106to 2.7010
6Pa at 30 C. The Young's modulus
(E) of these materials varies from 1.20 to 3.64 MPa with clay content ranging
from 0 to 10 wt%. The ratio of epoxy (ESO) to hydrogen (amino group of
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TETA) greatly affects dynamic and tensile mechanical properties. At higher
amount of TETA, nanocomposites exhibit stronger tensile and dynamic
properties.
Miyagawa et al (2005) reported the preparation of novel biobasednanocomposites from functionalized vegetable oil and organically-modified
layered silicate clay. They used anhydride-cured epoxidized linseed oil / or
octyl epoxide linseedate /diglycidyl ether of bisphenol epoxy matrix for the
preparation of nanocomposites. MMT is modified by methyl, tallow, bis (2-
hydrpxyethl) quaternary ammonium. It could be concluded from both the
TEM micrographs and XRD data that clay nanoplatelets were completely
exfoliated. Homogeneous dispersion and complete exfoliation result in the
excellent improvement for elastic modulus of clay nanocomposites.
Wibowo et al (2005) have investigated on cellulose acetate (CA)
nanocomposites. They were fabricated using extrusion followed by
compression molding or injection molding. Improvements in tensile strength
by approximately 38%, tensile modulus by approximately 33%, were observedafter adding (5 wt %) clay to fabricated CA plastic matrix. Incorporating a
small amount of appropriate compatibilizer is expected to enhance miscibility
of CA matrix and clay nanofillers and thus further improve mechanical and
thermal properties of the nanocomposites. Edible films or biobased
nanocomposites based on cellulose have been extensively applied to delay loss
of quality in fresh products such as tomatoes, cherries, fresh beans,
strawberries, mangoes and bananas. Cellulose derivatives such as hydroxyl
propyl cellulose, methylcellulose, carboxyl methyl cellulose and ethyl
cellulose are widely reported as Edible films and coatings in the scientific
literature.
Gindl et al (2005) produced cellulose based nanocomposite films with
different ratio of cellulose by means of partial dissolution of microcrystallinecellulose powder in lithium chloride/N,N-dimethylacetamide and subsequent
film casting. Mechanical and structural properties of the biobased
nanocomposites were measured. The films are isotropic, transparent to visible
light, highly crystalline. Results have shown that, by varying the cellulose
ratio, the mechanical performance of the nanocomposites can be tuned.
Depending on the composition, a tensile strength up to 240 MPa, an elastic
modulus of 13.1 GPa, and a failure strain of 8.6% were observed.
Petersson et al (2006) compared the mechanical and barrier properties
of two different types of biopolymer based nanocomposites. The two
nanoreinforcements chosen for this study were bentonite a layered silicate and
microcrystalline cellulose (MCC). The polymer matrix was poly lactic acid
(PLA). PLA is linear aliphatic thermoplastic polyester. The PLA/bentonitenanocomposite showed a 53% increase in tensile modulus and a 47% increase
in the yield strength compared to pure PLA. The PLA/S-MCC system on the
other hand showed no increase in tensile modulus and only a 12% increase in
yield strength compared to pure PLA. These results were lower than expected.
Also, the bentonite nanocomposite is able to reduce the oxygen permeability
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of the PLA while the MCC nanocomposite drastically increased the oxygen
permeability of the PLA.
Table 2.Comparison of the oxygen permeability of nanocomposite films andconventional synthetic polymer films
Ref
Unit
Permeability
(neat polymer/
nanocomposite)
Test
condition
Type of
polymer
)(Cebacedo,2004
(Ke , 2005)
)Maiti, 2003(
)Frunchi, 2006(
)Takahashi,2006(
)Guilbert, 1996(
)Guilbert, 1996(
)Guilbert, 1996(
)Guilbert, 1996(
5
2
3
10*6.3*
dayatmm
mcm
3
2
0.1cm mm
m d atm
Mpadaym
mmml
.
.2
218
*7.5*10.
m
s Pa
----
dayatmm
mmml2
.
dayatmm
mmml2
.
dayatmm
mmml2
.
dayatmm
mmml2
.
3.5/less than1
7.45/3.75
200/71
9.04/3.4
1.3/0.0247
57.5/---
4/---
190/---
91.4/---
45C,0%RH
---
STP
STP
30C
25C,27%RH
25C,42%RH
25C,92%RH
25C,91%RH
EVOH*
PET
PLA
PP
Butyl
rubber
Pectin
MC
Wheat
Gluten
Chitosan
*EVOH: Ethylene vinyl alcohol copolymer, PLA: Polylactide, PET: Poly ethylene
terephthalate, MC: Methyl cellulose, HDPE: High Density, poly ethylene, PP: Polypropylene
In spite of the fact that exact determination of gas permeability through
a biobased nanocomposite film is critical for food packaging industry, but
many of the researches reported in the literature indicated that there are a few
documents about measurement of gas permeability and effect of nanoclay on
it. Results illustrated in Table 2 reveal this fact. In regard to extensive
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researches on Edible films in different areas of food packaging industry,
therefore there is more information about most kinds of biopolymer which
have been used in formulation of Edible films. Table 3 indicates that many
papers have been published about the utilization of Edible films in variousareas of food packaging industry. But little attention has been paid to
application of biopolymers for production of biobased nanocomposites.
Table 3. Different type of biopolymer for preparation of Edible films and
Biobased nanocomposites in various areas food packaging industry
Type of
biopolymer
Edible film Biobased
nanocomposite
Lipid and
oil based
Polysaccharide
based
Carnauba wax (Mcgrath et al., 1955;
Gago et al., 2005; Baldwin, 1999),
Bees wax (Mcgrath et al., 1955; Gago
et al., 2005), Paraffin wax (Mcgrath et
al., 1955). Mineral oil (Mcnally,
1955), Vegetable oil (Seleeth et al.,
1965). Monoglycerides (Brissey et al.,
1961; Schneide, 1972), diglycerides
(Brissey et al., 1961; Schneide, 1972)
triglycerides (Schneide, 1972),
acetoglycerides (Woodmansee and
Abbott, 1958; aykes, 1959; Dawson et
al., 1962; Zabic et al., 1963; Stemmler
et al., 1979; Hirasa, 1991), acetylated
glycerol monostearate (Stuchell and
krochta, 1995; Jokay et al., 1967; Roth
and Mehltretter, 1967).
Starch and starch derivative: Hydroxy
propylated starch (Jokay et al., 1967;
Roth and Mehltretter, 1967)
Alginates (Berlin, 1975; Mountney
and Winter, 1961; Nelson 1963;Hartel, 1966), Carragineen (Stoloff et
al., 1948; Allinaham, 1949; Pearce
and Lavees, 1949; Meyer et al., 1959),
Dextran (Toulmin, 1959 a,b),
Cellulose ethers: Methylcellulose
Epoxidized soy bean
oil/OMM (Song et
al., 2006), Vegetable
oil / modified layered
silicate (Miyagawa et
al., 2005)
Chitosan/glassy
carbon electrode (Lu
et al., 1999; Misra et
al., 2006), Chitosan
/layered silicate
(Hedenqvist et al.,
2006),
Cellulose/ organoclay
(Misra et al., 2006;
Gindl and Keckes,
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Protein based
(Nelson and Fennema, 1991; Bauer
and Neuser 1969), hydroxypropyl
cellulose, hydroxylpropylmethyl
cellulose (Balasubramaniam 1994;
Anon, 1993), and carboxymethyl
cellulose [Baldwin, 1994; Funk et al.,
1971), Agar (Ayres, 1956; Nateajan
and Sheblon, 1995).
Collagen (Smits, 1985; Mullen, 1971;
Maser, 1987), Gelatin (Rice, 1994;
Harvard and Harmony, 1986; Morrisand parker, 1895; Klose et al., 1952;
Childs, 1957).
Milk protein: whey (Takahashi et al.,
2006; Heine et al., 1979; Keil et al.,
1960; Chen, 1995; Mate and Krochta,
1995; Morean and Rosenberg, 1993;
Rosenberg and young, 1993; Young et
al., 2003, Sheu and Rosenberg, 1994),
casein (Stemmler M and H, 1974).
Cereal protein: Corn zeins (Hargen,
1995; Clark and Ralow, 1949; Herald,
1996), Wheat gluten (Gennadois andWeller, 1992), soy protein isolate
(Stuchell et al., 1994; Roy et al.,
1995).
2005; Wibowo et al.,
2005; Petersson et al,.
2006), starch /MMT
(Park et al., 2003;
Chen and Evann,
2005; Huang et al.,
2006; Park et al.,
2002, 2003; Avella et
al., 2005)
Whey protein isolate
(Hedenqvist et al.,
2006),
As mentioned before, to select biobased nanocomposite packaging
materials, it is very important to know deteriorative reactions in food products.
Deteriorative chemical changes in foods include nonenzymatic browning, lipid
hydrolysis, lipid oxidation, protein denaturation, protein cross linking,
hydrolysis of proteins and oligo and polysaccharides, polysaccharide
synthesis, degradation of natural pigments and glycolytic changes. After
recognition of degradation reaction in food product (refer to Table 1), required
gas composition is determined approximately. Then, optimum rate of gas
permeability can be calculated. So, base on this information, type of
biopolymer will be selected (Table 3). In regard to type of biopolymer,
amount of nanoclay, optimum thickness of biobased nanocomposite film, type
of compatibilizing agents and also preparation method should be determined.
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