CHAPTER 2 REVIEW OF LITERATURE - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/43340/11/11_chapter2.pdf · 11 CHAPTER 2 REVIEW OF LITERATURE This chapter deals with the scientific

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CHAPTER 2

REVIEW OF LITERATURE

This chapter deals with the scientific work carried out by

researchers in developing the edible film/coating, their properties and

in turn enhancing the value, quality and shelf life of foods in general

and of fruits and vegetables in particular. The chapter is divided into 4

sections namely

2.1 Formulation of edible film

2.2 Properties of edible film

2.3 Preservation of food by using edible coating/film

2.4 Edible film as means of fortification.

2.1 Formulation of Edible Film

Edible films can be prepared from various biobased materials

like carbohydrates, proteins, fat and waxes and combination thereof.

The properties of film are modified with addition of compounds like

plasticizers and cross linking agents. The edible films designed for a

particular food must be compatible with the product and also meet

the requirements of that product. The current topic is divided into

three sub topics namely

2.1.1 Protein based edible films

2.1.2 Carbohydrate based edible films

2.1.3 Composite edible films

2.1.1 Protein Based Edible Films

The protein as a source of edible films provides very good

mechanical properties like tensile strength, elongation at break and

modulus of elasticity but the problem with protein based films is that

they are poor water vapour and gas barrier properties. The research

work associated with protein based edible film is as summarized

below.

Review of Literature

12

Piermaria et al, (2011) evaluated the ability of kefiran to form

films and the effect of glycerol addition at different concentrations on

film properties. Kefiran was able to form films at concentrations

ranging from 5 to 10 g/kg. The concentration 10 g/kg was selected

because the films were easily removed from the plate. These films

exhibited good water vapor barrier properties and the addition of 25 g

of glycerol per 100 g of polysaccharide allowed the optimum value of

4.09 X 10-11 g/m s Pa to be obtained. Films without glycerol were

brittle and rigid since they showed high Young‘s modulus and tensile

strength values and low deformation at break. Glycerol addition led to

extremely high elongation values, allowing flexibilities comparable to

those of synthetic materials.

Denavi et al, (2009) investigated the influence of drying

conditions on edible films prepared from commercial soy protein

isolate (CSPI) and laboratory prepared soy protein isolate (LSPI) The

films were dried in a chamber with air circulation under controlled

conditions of relative humidity (24, 30, 45, 60, 66 percent) and air

temperature (34, 40, 55, 70, 76 ºC). It was found that mechanical

properties of films made from LSPI and CSPI are influenced in a very

different way by the drying conditions due to a diverse initial protein

conformation in both materials

Mastromatteo et al, (2008) investigated the individual and

interactive effects of the spelt and wheat bran as well as glycerol, on

the properties of wheat gluten based edible films. Results highlight

that the glycerol presence had a negative effect on water vapor

permeability (WVP) values of the films (increase of WVP), whereas the

bran presence had a positive influence (decrease of WVP). The Young‘s

Modulus of the composite films increased with the increase of bran

concentration and with the decrease of glycerol.

Cho et al, (2007) prepared edible films from membrane

processed soy protein concentrate at various film forming solution

pHs. Their mechanical, barrier, and physical properties were


13

compared with soy protein isolate films. As the film solution pH

increased from 7 to 10, the resulted MSC films were more

transparent, yellowish, and had lower oxygen permeability. However,

tensile strength, Young‘s modulus and water vapor permeability of

MSC films were not affected by film solution pHs.

Bamdad et al, (2006) prepared edible film from lentil protein

concentrate (LPC) by using LPC (5 g/100 ml water) and glycerin (50

percent, w/w of LPC). Water Vapour Permeability values and other

characteristics of the lentil protein-based edible films were comparable

with other edible protein films. LPC film had more red and less yellow

color; it was also observed that the film had good mechanical

properties and water vapor permeability together with good solubility.

Taylor et al, (2005) examined several food compatible solvents

to replace aqueous ethanol, commonly used for prolamin film casting.

Glacial acetic acid and lactic acid were identified as the best primary

solvents and 55 percent (w/w) aqueous isopropanol as a good binary

solvent. The sensory, tensile, and water barrier properties of the films

cast from glacial acetic acid at 25 0C and aqueous ethanol at 700C

were almost the same. However, the use of glacial acetic acid at 25 0C

for casting kafirin films is advantageous as it gave films of more

consistent quality.

Vanin et al, (2005) studied the effect of plasticizers and their

concentrations on the thermal and functional properties of gelatin-

based films. Four polyols (glycerol—GLY, propylene glycol—PPG, di-

DTG and ethylene glycol—ETG) were used in five concentrations: 10,

15, 20, 25, and 30 g plasticizer/100 g of gelatin to prepare the film.

Plasticizer effect and efficiency were observed with DTG and ETG on

the thermal properties, and with the GLY in terms of functional

properties.

de Carvalho and Grosso (2004) found that protein films

possess good gas barrier properties at low to intermediate relative

humidity but reduced water vapor barrier properties, which limits


14

their application. The introduction of chemical or enzymatic

modifications could be an alternative to improve the cohesion

properties of the polymeric matrix due to the formation of cross-

linkages, thus improving the barrier characteristics and the

mechanical resistance and decreasing the film solubility.

Hernandez-Munoz et al, (2004) studied the effect of cross-

linking agents glutaraldehyde (GTA), glyoxal (GLY) and formaldehyde

(FA) on relevant properties of films based on a glutenin-rich fraction

from commercial wheat gluten. The gliadin-rich fraction was separated

from glutenin-rich fraction using 70 percent (v/v) aqueous ethanol

solution. The 70 percent ethanol-insoluble fraction (glutenin-rich

fraction) was dispersed in 50 percent (v/v) aqueous ethanol at 400C

and pH 5. GTA, GLY or FA was added in concentrations of 2, 4 and 8

percent (g/100 g dry protein) to the film-forming solution. Films were

cast and dried at 230C and 40 percent relative humidity (RH) for 10 h.

Water vapour permeability values decreased by around 30% when FA,

GTA or GLY were incorporated. The highest tensile strength values

were obtained using FA, followed by GTA and GLY. Glass transition

temperature of cross-linked films shifts to slightly higher values when

cross-linking agents were used. Films treated with GTA and GLY were

darker with a yellowish color. Addition of concentrations up to 2% of

cross-linker did not modify the properties of the films. Water sorption

behavior of control and cross-linked films did not differ.

Gennadios et al, (1993) evaluated the effect of pH of film

forming solution of Soy protein isolate (SPI) and wheat gluten (WG)

films. They observed that WG films formed within pH 2-4 and 9-13,

whereas SPI films formed within pH 1-3 and 6-12. Film formation was

inhibited by poor protein dispersion around the isoelectric pH region

of SPI (pH 4.5) and WG (pH 7.6). Film formation was inhibited by poor

protein dispersion around the isoelectric pH region of SPI (pH 4.5) and

WG (pH 7.6). SPI films prepared from pH 6 to 11 had significantly

higher TS, higher E, and lower WVP than films from pH 1 to 3. WG


15

films produced under alkaline conditions had significantly higher TS

than films processed under acidic conditions. The research related to

formulation of protein based edible film is summarized in Table 2.1

2.1.2 Carbohydrate Based Edible Films

Bourtoom and Chinnan (2008) developed biodegradable blend

films from rice starch chitosan by casting film-solution on leveled

trays. The influence of the ratio of starch and chitosan (2:1, 1.5:1, 1:1,

and 0.5:1) on the mechanical properties, water barrier properties, and

miscibility of biodegradable blend films was investigated. The

biodegradable blend film from rice starch chitosan showed an increase

in tensile strength (TS), water vapor permeability (WVP), lighter color

and yellowness and a decreasing elongation at the break (E ), and film

solubility (FS) after incorporation of chitosan. However, the WVP of

rice starch chitosan biodegradable film was characterized by relatively

lower WVP than chitosan films but higher than polyolefin.

Fadnis et al, (2008) studied the miscibility of Hydroxy propyl

methyl cellulose (HPMC)/polyvinyl alcohol (PVA) blends edible polymer

films. It was revealed that HPMC/PVA blend is miscible when the

HPMC content is more than 60 percent in the blend at 30 and 50 0C

and also that the change in temperature in the range of experiment

has no significant effect on the miscibility of HPMC/PVA polymer

blend.

Pinotti et al, (2007) analyzed the effect of an electrical field

applied during drying on microstructure and macroscopic properties

of films obtained with different mixtures of chitosan (CH) and methyl

cellulose (MC). CH treated films showed higher Young‘s Modulus

values than the control ones; in composite control samples, YM and

tensile strength increased with CH concentration, leading to stronger

films.


16

Table 2.1 Review on Formulation of Protein Based Edible Films

Sr

No.

Author Year Important finding

1 Piermaria et

al

2011 Edible films can be obtained from kefirin

by using glycerol as plasticizer

2 Denavi et al 2009 Drying conditions like RH and air

temperature affects on mechanical

properties of film.

3 Mastromatteo

et al

2008 Addition of bran positively affects the

WVP value whereas glycerol has negative

effect.

4 Cho et al 2007 Various properties of edible film from soy

protein isolate and membrane processed

soy protein concentrate were compared

5 Bamdad et al 2006 Edible films can be prepared from lentil

protein concentrate and their properties

are comparable with other protein films.

6 Taylor et al 2005 Aqueous ethanol can be replaced by

several food compatible solvents like

glacial acetic acid and lactic acid for

prolamine film casting.

7 Vanin et al 2005 Different plasticizers affect on thermal

and functional properties of gelatin

based edible film.

8 de Carvalho

and Grosso

2004 Water vapor barrier properties of protein

films can be improved through chemical

or enzymatic modifications.

9 Hernandez-

Munoz

2004 Different cross linking agents have their

effect on properties of wheat gluten film.

10 Gennadios et

al

1993 Wheat gluten and soy protein isolate

films requires different pH values for film

formation.


17

Muller et al, (2008) investigated the effects of plasticizer

namely glycerol and sorbitol on the water sorption isotherms and

water vapor permeability (WVP) of cassava starch films prepared by

casting. The WVP values were determined in three ranges of RH, (2–33

percent, 33–64 percent and 64–90 percent). In all cases, an increase

in WVP values was observed with increasing plasticizer concentration

and RH.

Paes et al, (2008) investigated the effect of the paste

preparation conditions on the properties of cassava starch paste and

its films. The films were prepared by casting starch pastes gelatinized

under eight different conditions: 70, 80, 90 or 100 0C at high (18,000

rpm) and low shear rate (150 rpm). It was shown that the use of a

high shear affected all mechanical properties determined by tensile

tests, which were lower for all temperatures compared to the films

prepared using low shear rate.

Alves et al, (2007) produced cassava starch films by casting.

The effects of different amylose quantities (6.3, 15.6 and 25.0 g/100 g

of starch) and glycerol contents (20.0, 32.5 and 45.0 g/100 g of

starch) on filmogenic solution were evaluated. The enrichment of

filmogenic solutions with amylose solution originates stronger and

more permeable films. Glycerol behaved as a typical plasticizer in

starch films; with increasing glycerol concentration, WVP, strain at

break and puncture deformation increased, and elongation at break,

YM and puncture strength decreased.

Tapia-Blacido et al, (2005) studied the filmogenic capacity of

amaranth flour films were obtained by casting process using glycerol

as plasticizer. The biofilms presented a yellowish color, moderate

clarity, and high flexibility but low tensile strength. Nevertheless they

showed less oxygen and water permeability than other protein and

polysaccharide films. The review of literature related to formulation of

carbohydrate based film can be summarized as shown in Table 2.2


18

Table 2.2 Review on Formulation of Carbohydrate Based Films.

Sr

No.


1 Bourtoom

and

Chinnan

2008 The biodegradable blend film prepared

from rice starch and chitosan shows

increase in tensile strength and water

vapour permeability and decrease in

elongation at break and solubility after

incorporation of chitosan.

2 Fadnis et

al

2008 Hydroxyl propyl methyl cellulose

/polyvinyl alcohol blend is miscible

when HPMC content is more than 60

per cent at 30 and 500C

3 Pinotti et

al

2007 Chitosan treated films showed higher

Young‘s Modulus values than the

control ones; in composite control

samples, Young‘s Modulus and tensile

strength increased with chitosan

concentration, leading to stronger

films.

4 Muller et

al

2008 The WVP values of Cassava starch

edible films are increases with

increase in plasticizer concentration

and RH.

5 Paes et al 2008 In case of cassava starch films the

high shear rates affect all mechanical

properties.

6 Alves et al 2007 The enrichment of cassava starch film

with amylose increases strength and

permeability of film.

7 Tapio-

Blacido et

al

2005 Amaranth flour with glycerol gives

films with high flexibility but low

tensile strength, oxygen and water

vapor permeability


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2.1.3 Composite Edible Films

Vargas et al, (2008) prepared edible films based on high

molecular weight chitosan (CH) and different concentrations of oleic

acid (OA). Results showed that higher the OA content, the lower the

WVP and the moisture sorption capacity. In general, the addition of

OA into the CH matrix leads to significant increase in gloss and

translucency and decrease in the tensile strength, elongation at break

and Young‘s modulus of the composite films. The mechanical and

optical properties of the films were related with their microstructure,

which was observed by Scanning Electron Microscope.

Gounga et al, (2007) prepared edible films from whey protein

isolate (WPI), five percent, seven percent and nine percent (w/v) WPI

were used at three WPI:Gly ratios (3.6:1; 3:1; and 2:1). Five percent

WPI with a 3.6:1 WPI:Gly ratio showed the best combination with

factors considered being thickness and water vapor permeability

(WVP), while the nine percent WPI with 3.6:1 WPI:Gly showed the best

result as seen from the oxygen permeability (OP). Further studies were

conducted by adding pullulan (PUL) at different WPI:PUL ratios (1:0;

1:1; 2:1; 3:1; 4:1; 5:1; 6:1; 8:1; 10:1) to the selected film. WPI–PUL

film had a good appearance and 1:1 WPI: PUL resulted in films with

greatest values of OP, WVP and transmittance.

Bertan et al, (2005) found that composite edible/degradable

films produced with hydrocolloids and lipids can result in better

functionality than films produced with the components, especially

with respect to their barrier properties. Of the lipids, waxes produce

the best water vapor barrier properties, but produce fragile/brittle

films. Films with the addition of acids, and the blend with elemi

presented better water vapor barrier properties as compared to the

gelatin/triacetin film. The mechanical resistance decrease with the

addition of the lipids. However the opacity and soluble matter

increased.


20

Xu et al, (2005) prepared chitosan/starch composite films by

combining chitosan (deacetylated degree, 90 percent) solution and two

thermally gelatinized corn starches (waxy starch and regular starch

with 25 percent amylase). Regardless of starch type, both the Tensile

Strength (TS) and Percent Elongation (E) of the composite films first

increased and then decreased with starch addition. Composite film

made with regular starch showed higher TS and E than those with

waxy starch. The addition of starch decreased WVTRs of the composite

films

Yu et al, (2004) investigated the effect of carboxymethyl

cellulose on the aggregation of formulation based on calcium

caseinate, commercial whey protein, and a 1:1 mixture of soy protein

isolate and whey protein isolate. The aggregation behavior was

enhanced by means of physical treatments, such as heating at 900C

for 30 min or gamma-irradiation at 32 kGy. A synergy resulted from

the combination of CMC to gamma-irradiation in Caseinate/CMC and

SPI/WPI/CMC formulations.

Ryu et al, (2002) prepared the edible composite films using

high-amylose corn starch (HACS) and corn zein. HACS was gelatinized

using the specially designed high-pressure container. The HACS film

containing 20 g sorbitol/100 g as a plasticizer had suitable physical

properties. The HACS film coated with corn zein containing 20 g oleic

acid/100 g had moderate physical properties and barrier properties.

Chen and Nussinovitch (2000) introduced xanthan gum into a

traditional, wax-based coating formulation for easy peelers. The

xanthan created disturbances in the ordered, regular structure of the

traditional wax coating, as observed by electron microscopy. In

addition, less off-flavors were detected by sensory evaluation of juice

extracted from the fruit coated with the wax–xanthan coating

Arvanitoyannis et al, (1998) prepared films of chitosan and

gelatin by casting their aqueous solutions (pH < 4.0) at 600C and

evaporating at 22 or 600C (low- and high-temperature methods,


21

respectively) and plasticized with water or polyols. They found that an

increase in the total plasticizer content resulted in a considerable

decrease of Young‘s modulus and tensile strength (up to 50 percent of

the original values when 30 percent plasticizer was added), whereas

the percentage elongation increased (up to 150 percent compared to

the original values).

Rhim et al, (1998) determined the effect of dialdehyde starch

(DAS) on selected physical properties of cast soy protein isolate (SPI)

films. Films were cast from heated (70°C for 20 min) alkaline (pH 10)

aqueous solutions of SPI at 5 g: 100 ml water, glycerin (50 percent, w:

w, of SPI), and DAS at 0, 5, 10, 15, or 20 percent (w: w) of SPI. The

DAS addition increased film yellowness suggesting occurrence of

cross-linking between SPI and DAS. The films with 5 or 10 percent

DAS had increased TS compared to control films, whereas film E was

not significantly affected by DAS. Small increases in WVP and MC

were observed for DAS containing films.

Shih (1996) prepared edible films using a combination of rice

protein concentrate and the polysaccharide pullulan and observed

that the protein-pullulan mixture with up to 50 percent protein

concentrate could be cast on a glass plate. into films with tensile

strength of about 18 MPa and water vapor permeability of 40 g x

mil/m2 x day x mmHg. Film strength and water vapor resistance were

improved by the addition of small amounts of propylene glycol alginate

under alkaline condition. Oils were also incorporated into the film for

improved water vapor resistance. The review of literature related to

formulation of composite edible film can be summarized as shown in

Table 2.3


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Table 2.3 Review on Formulation of Composite Edible Films

Sr

No.


1 Vargas et al 2008 In chitosan oleic acid composite film

increased amount of oleic acid increases

gloss and translucency while decreases

WVP, tensile strength and elongation at

break.

2 Gounga et al 2007 Optimization of concentration of whey

protein isolate, glycerol and pullulan.

3 Bertana et al 2005 Edible films produced with

hydrocolloids and lipid can result in

better functionality than films produced

with individual components.

4 Xu et al 2005 In chitosan starch composite films

comosition and type of starch used

affects on properties of edible film.

5 Yu et al 2004 Composite edible film from

carboxymethyl cellulose, whey protein

isolate, soy protein isolate and calcium

caseinate the aggregation behavior can

be modified by treatments like heating

and gamma irradiation.

6 Ryu et al 2002 The high amylase corn strach film

coated with corn zein containing 20 g

oleic acid/100 g had moderate physical

properties and barrier properties.

7 Chen and

Nussinovitch

2000 Xanthan gum creates disturbance in

ordered, regular structure of traditional

wax coating.

8 Arvanitoyannis

et al

1998 In chitosan gelatin film increase in total

plasticizer content decreases Young‘s

modulus and tensile strength while

percent elongation increases.

9 Rhim et al 1998 Addition of dialdehyde starch to soy

protein isolate film increases yellowness,

tensile strength and WVP values.

10 Shih 1996 Satisfactory edible film can be obtained

from rice protein concentrate and

pullulan


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2.2 Properties of Edible Film

Edible films are biodegradable , able to act as moisture, gas,

aroma and lipid barriers. Various natural materials like

polysaccharides, lipids and proteins have been used to prepare edible

films. The properties of edible films have been reported to be affected

considerably by different factors at different stages of the process, like

a) nature and composition of biopolymers b) nature of plasticizers and

degree of plasticization, c) Presence of functional additives(cross

linking agents), d) processing parameters (temperature, pH, nature of

mixing, drying etc).

The overall properties of edible films studied are grouped into

following three subcategories

2.2.1 Barrier properties

2.2.2 Mechanical properties

2.2.1 Barrier Properties

Ghanbarzadeh et al, (2007) prepared zein based edible films

by using sugars (fructose, galactose and glucose) as plasticizers. They

found that the pure zein film had high WVP and adding of sugars to

0.7 g/g zein led to decrease of WVP. The films containing galactose

had the lowest WVP.

Sothornvit and Pitak (2007) investigated the effect of banana

flour, glycerol (Gly) and pectin content on film oxygen permeability

(OP) and mechanical properties of banana films. Banana flour content

significantly affected film OP; whereas, Gly and pectin contents did

not significantly affect film OP.

Srinivasa et al, (2007) prepared chitosan films by blending

with polyols (glycerol, sorbitol and polyethylene glycol (PEG)) and fatty

acids (stearic and palmitic acids). The glycerol blend films showed

decrease, whereas sorbitol and PEG blend films showed increase in

the water vapor permeability (WVP) values. No considerable

differences in WVP were observed in fatty acid blend films.


24

Mali et al, (2006) prepared edible film from corn, cassava and

yam starch with glycerol as plasticizer and observed that unplasticized

films showed water vapor permeability (WVP) values ranged from 6.75

to 8.33 x 10-10 g m-1 s-1 Pa-1. These values decrease when glycerol

content reached at 20 g/100 g starch because a more compact

structure was formed and, then, at 40 g glycerol/100 g starch,WVP

increased because film matrixes became less dense.

Prodpran and Benjakul (2005) studied the effect of acid and

alkaline solubilizing processes on the properties of the protein based

film from surimi. Film with alkaline process had slightly lower water

vapor permeability (WVP), compared to that prepared by acid

solubilizing process. Increase in protein concentration resulted in an

increase in WVP.

Ayranci and Tunc (2003) examined the effects of the presence

of stearic acid (SA), ascorbic acid (AA) and citric acid (CA), in varying

amounts in the film composition, on the oxygen permeability (OP) of

methyl cellulose based edible films. The OP increased with increasing

SA content of the film and decreased with the inclusion of AA or CA in

the film composition.

Paramawati et al, (2003) prepared zein based edible films

plasticized individually with 20 percent lauric acid; octanoic acid;

triethylene glycol; polyethylene glycol, or lactic acid. Both octanoic

acid and lactic acid did not affect on water vapor and oxygen

permeability (WVP and OP). Lauric acid exhibited improved WVP and

OP values. On the other hand triethylene glycol and polyethylene

glycol did not affect the existing good performance of barrier properties

of films

Gaudin et al, (2000) found that sorbitol had an

antiplasticisation effect for contents below 21 percent (wt percent), as

indicated by a ten-fold drop in oxygen permeability of starch based

film. It was 1.43 x 10-16 cm3 cm/cm2 s Pa for the sample not

containing sorbitol and 0.15 x 10-16 cm3 cm/cm2 s Pa for the sample


25

containing 8.8 percent of sorbitol. For sorbitol contents above 21

percent (wt percent), oxygen permeability increased slightly.

Yang and Paulson (2000) incorporated bees wax or a 1:1 blend

of stearic-palmitic acids (S-P) into gellan films through emulsifcation

to form gellan/ lipid composite films. Addition of the lipids to gellan

films significantly improved the WVP. Bees wax was more effective

than S-P acids in reducing the WVP

Banerjee and Chen (1995) compared the functional properties

of whey protein concentrate films with those of the films derived from

sodium caseinate, potassium caseinate, calcium caseinate, and whey

protein isolate. Water vapor permeability of simple whey protein

concentrate film was lower than that for films of sodium caseinate,

potassium caseinate, and whey protein isolate. Composite whey

protein concentrate film had the lowest water vapor permeability of all

the milk protein films.

Park and Chinnan (1995) made edible films from proteins

(corn-zein and wheat gluten) and celluloses (methyl cellulose and

hydroxypropyl cellulose), and tested for permeability of gases. Oxygen

and carbon dioxide permeabilities of edible films were generally lower

than those of plastic films. However, water vapor permeabilities of

edible films were higher than those of plastic films. The concentration

of plasticizer significantly affected the permeability of gases. The gas

permeabilities, O2, CO2 and water vapor, of cellulose films increased

as the concentration of plasticizer increased. Addition of lipid in the

hydroxypropyl cellulose (HPC) film decreased the gas permeability

linear relationships were found between permeability of gases and film

thickness in protein films. The research related to study of barrier

properties of film can be summarized as shown in Table 2.4


26

Table 2.4 Review on Barrier Properties of Edible Film

Sr

No.


1 Ghanbarzadeh

et al

2007 WVP values of zein films can be

lowered by addition of sugars

2 Sothornvit and

Pitak

2007 In a composite edible film banana

flour affects film oxygen

permeability whereas glycerol and

pectin does not affect significantly

3 Srinivasa et al 2007 Glycerol as plasticizer in chitosan

film decreases WVP values while

sorbitol and polyethylene glycol

increases it.

4 Mali et al 2006 The WVP values of a edible film from

corn, cassava and yam starch

initially decreases with increase in

amount of plasticizer and then it

increases.

5 Prodpran and

Benjakul

2005 Acidic or alkaline solublizing

process affects on barrier properties

of surimi protein film

6 Ayranci and

Tunc

2003 Methyl cellulose based edible films

shows increase in oxygen

permeability with increasing stearic

acid content while ascorbic acid and

citric acid found to decrease it.

7 Paramawati et

al

2003 In case of Zein films octanoic acid,

lactic acid Lauric acid triethylene

glycol and polyethylene glycol as a

plasticizer exhibited different effects

on WVP and OP values.


27

8 Gaudin et al 2000 In starch based edible film sorbitol

has antiplasticization effect below

21 percent level decreasing the

oxygen permeability values and

above this level oxygen permeability

increased slightly.

9 Yang and

Paulson

2000 Addition of lipids to gellan films

significantly improves the WVP

10 Banejee and

Chen

1995 Water vapor permeability of simple

whey protein concentrate film was

lower than that for films of sodium

caseinate, potassium caseinate, and

whey protein isolate.

11 Park and

Chinnan

1995 Oxygen and carbon dioxide

permeability of edible films are

generally lower, however water

vapour permeability is film is higher

than those of plastic films,

2.2.2 Mechanical Properties

Fabra et al, (2008) optimize film composition in terms of kind

and ratio of plasticizer (glycerol and sorbitol) and lipids (oleic acid and

bees wax) for sodium caseinate based films. The glycerol was more

effective as plasticizer than sorbitol in the caseinate matrices; films

with 90 percent sorbitol had similar tensile properties to those

elaborated with 40–50 percent glycerol. Oleic acid, pure or mixed with

bees wax, has a plasticizing effect in the films, increasing their

elasticity, flexibility and stretchability. The films with a 1:0.3:0.5

protein:glycerol:lipid ratio containing a 70:30 OA:BW ratio were the

ones which showed the most adequate functional properties. (Young‘s

Modulus: 29.01 ± 9.36 MPa, Elongation at break: 23.90 ± 2.05,).


28

Ozdemir and Floros (2008) investigated the effect of protein,

sorbitol, bees wax and potassium sorbate concentrations in whey

protein films. Protein, sorbitol and potassium sorbate were important

factors influencing ultimate tensile strength, Young‘s modulus and

elongation. Bees wax did not have an impact on ultimate tensile

strength and Young‘s modulus, and it had little effect on elongation.

Cao et al, (2007) found that in soy protein isolate gelatin

composite edible film increasing gelatin ratio increased tensile

strength (TS), elongation to break (EB), Young‘s modulus and swelling

property of the SPI/gelatin composite films.

Kristo, et al (2007) investigated mechanical properties of

pullulan (P) and sodium caseinate (SC), as well as their blend and

bilayer films plasticized with sorbitol (25 percent dry basis). Increasing

the P/SC ratio decreased the Young‘s modulus (E), the tensile

strength (rmax) and increased the percent elongation at break (percent

EB), suggesting that P imparts flexibility and SC stiffness to the

composite films.

Sothornvit and Pitak (2007) investigated the effect of banana

flour, glycerol (Gly) and pectin content on film oxygen permeability

(OP) and mechanical properties of banana films. Increasing banana

flour and pectin contents enhanced film strength; thus, it showed

higher Young‘s modulus and tensile strength (TS) values but less

percent elongation values. In contrast, increasing glycerol content

reduced the film strength and improved film flexibility; therefore, it

decreased EM and TS values but increased percent elongation values.

Banana films showed good sealability, which can make these films

suitable as sachets or pouches for dry foods, thus reducing the need

for plastic materials.

Srinivasa et al, (2007) prepared chitosan films by blending

with polyols (glycerol, sorbitol and polyethylene glycol (PEG)) and fatty

acids (stearic and palmitic acids). The tensile strength of the blended

films decreased with the addition of polyols and fatty acids, whereas


29

the percent elongation was increased in polyol blend films, but fatty

acid blend films showed no significant differences.

Prodpran and Benjakul (2005) studied the effect of acid and

alkaline solubilizing processes on the properties of the protein based

film from threadfin bream surimi. Surimi films prepared from both

processes had the similar light transmission, tensile strength (TS) and

elongation at break (EAB). Increase in protein concentration resulted

in an increase in TS, and EAB.

Fakhouri, et al , (2004) developed and characterized

composite biofilms using wheat gluten and cellulose acetate phthalate.

They observed that an increase in gluten concentration in the

composite films resulted in a decrease in tensile strength. There was

no significant difference in elongation at break between the composite

films. No difference in thickness was detected either.

Turhan and Sahbaz (2004) investigated tensile strength (TS),

percent elongation (E), in methylcellulose (MC) films plasticized by

polyethylene glycol (PEG). TS determined to be between 17 and 44

N/mm2 and percent E between 14 percent and 97 percent, depending

on composition.

Paramawati et al, (2003) prepared zein based edible films

plasticized individually with 20 percent lauric acid; octanoic acid;

triethylene glycol; polyethylene glycol, or lactic acid. They observed

that all plasticizer indicated increased film flexibility and also affected

tensile properties. Both octanoic acid and lactic acid increased all

tensile parameters such as tensile strength (TS), puncture strength

(PS) and elongation to break (ETB). Lauric acid exhibited improved TS

and PS values. On the other hand triethylene glycol and polyethylene

glycol did not affect the existing good performance of tensile

properties of films, however, polyethylene glycol indicated excellent in

improving film flexibility.


30

Rhim et al, (2002) determined the effect of sodium dodecyl

sulfate (SDS) on selected physical properties of glycerin-plasticized soy

protein isolate (SPI) films. Films were cast from heated (70 °C for 20

min), alkaline (pH 10) aqueous solutions of SPI (5 g/100 ml water),

glycerin (50 percent w/w of SPI), and SDS (0, 5, 10, 20, 30, or 40

percent w/w of SPI). SDS reduced film TS by as much as 43 percent

for films with 40 percent SDS (6.2 vs. 10.9 MPa for control SPI films).

In contrast, film E increased notably with addition of SDS even at 5

percent.

Paramawati et al, (2001) observed the effects of the proportion

of polyethylene glycol (PEG) and lauric acid (LA) used as composite

plasticizer on mechanical properties of zein-based film. Flexibility of

plasticized-zein films increased as the portion of PEG was increased,

as shown by the trend of decreasing Young‘s modulus (EM) and

increasing elongation to break (ETB). Tensile and puncture strength

values were also affected by increase in the PEG portion, although

they were not as consistent as EM and ETB values.

Yang and Paulson (2000) incorporated bees wax or a 1:1

blend of stearic-palmitic acids (S-P) into gellan films through

emulsifcation to form gellan/ lipid composite films. Addition of the

lipids to gellan films lowered the mechanical properties and films with

bees wax showed better mechanical properties overall than those with

S-P acids. The tensile properties of gellan films containing 14.3percent

bees wax were evaluated as a function of water activity (aw) of the

film. Increasing the aw decreased the tensile strength (TS) and

Young‘s modulus but tensile elongation was not affected. The extent of

the decreases in TS for the composite film was less pronounced than

that for a similar film without lipids, suggesting that lipids help to

alleviate moisture sensitivity of gellan films.


31

Jangchud and Chinnan (1999) formed peanut protein films by

using four types of plasticizer (glycerin, sorbitol, polyethylene glycol

and propylene glycol)at three levels (0.67, 1.17, 1.67 g/g of protein

content). Tensile strength decreased (from5.14 to 4.10 MPa), with an

increase of glycerin from 1.17 to 1.67 g/g of protein and percent

elongation increased (from 105 to 164 percent) when glycerin

increased from 0.67 to 1.67 g/g of protein

Banerjee and Chen (1995) compared the functional properties

of whey protein concentrate films with those of the films derived from

sodium caseinate, potassium caseinate, calcium caseinate, and whey

protein isolate. The ultimate tensile strengths of simple whey protein

concentrate films were similar to those of caseinate films. Whey

protein concentrate films exhibited lower puncture strengths than did

films from other milk proteins except simple film from sodium

caseinate. Whey protein concentrate and isolate films had higher

elongation values than did simple calcium caseinate films.

Gennadios et al, (1993) evaluated the effect of pH of film

forming solution of Soy protein isolate (SPI) and wheat gluten (WG)

films. He found that SPI films prepared from pH 6 to 11 had

significantly higher Tensile Strength(TS) and higher Elongation at

break (E) than films from pH 1 to 3. WG films produced under alkaline

conditions had significantly higher TS than films processed under

acidic conditions. The research related to mechanical properties of

edible film can be summarized as shown in Table 2.5


32

Table 2.5 Review on Mechanical Properties of Edible Film

Sr

No.


1 Fabra et al, 2008 Sodium caseinate films are affected by

kind and ratio of plasticizer and lipids.

2 Ozdemir

and Floros

2008 In whey protein film protein, sorbitol

and potassium sorbate influence

tensile strength, young‘s modulus and

elongation.

3 Cao et al 2007 In soy protein isolate gelatin composite

edible film increasing gelatin ratio

increased tensile strength, elongation

to break , Young‘s modulus and

swelling property

4 Kristo, et al 2007 Increasing the Pullulan/Sodium

Caseinate ratio decreases the Young‘s

modulus, tensile strength) and

increases the percent elongation at

break.

5 Sothornvit

and Pitak

2007 Increasing banana flour and pectin

contents enhances film strength while

increasing glycerol content reduces

film strength and improves film

flexibility in banana flour based edible

film.

6 Srinivasa et

al

2007 The tensile strength of the blended

chitosan films decreases with the

addition of polyols and fatty acids,

whereas the percent elongation

increases in polyol blend films

7 Prodpran

and

Benjakul

2005 In case of protein based film from

threadfin bream surimi increase in

protein concentration resulted in an

increase in TS, and EAB.

8 Fakhouri,

et al

2004 In wheat gluten and cellulose acetate

phthalate composite film increase in

gluten concentration results in

decrease in tensile strength.


33

9 Turhan

and Sahbaz

2004 Investigated tensile strength (TS),

percent elongation (E), in

methylcellulose (MC) films plasticized

by polyethylene glycol (PEG).

10 Paramawati

et al

2003 In zein based edible films all

plasticizer increases film flexibility and

also affected tensile properties.

11 Rhim et al 2002 In glycerin-plasticized soy protein

isolate (SPI) films Sodium Dodecyl

Sulphate (SDS) reduces film Tensile

strength, while elongation at break

increased notably with addition of

SDS.

12 Paramawati

et al,

2001 Flexibility of plasticized-zein films

increases as the amount of

Polyethylene Glycol increases tensile

and puncture strength values are also

affected by increase in the PEG

content,

13 Yang and

Paulson

2000 Addition of the lipids to gellan films

lowers the mechanical properties and

films with bees wax shows better

overall mechanical properties than

those with blend of stearic palmitic

acids

14 Jangchud

and

Chinnan

1999 In peanut protein films tensile

strength decreases with an increase of

glycerin from 1.17 to 1.67 g/g of

protein and percent elongation

increases when glycerin increased

from 0.67 to 1.67 g/g of protein

15 Banerjee

and Chen

1995 Compared the functional properties of

whey protein concentrate films with

those of the films derived from sodium

caseinate, potassium caseinate,

calcium caseinate, and whey protein

isolate.

16 Gennadios

et al

1993 SPI films prepared from pH 6 to 11

had significantly higher tensile

strength and higher elongation at

break than films from pH 1 to 3.


34

2.3 Preservation of Foods by Using Edible Coating /Film

Edible films and coatings can be used to help in the

preservation of fruit and vegetables because they provide a partial

barrier to moisture, O2 and CO2, also improving mechanical handling

properties, carrying additives, avoiding volatiles loss and even

contributing to the production of aroma volatiles Edible surface

coatings are applied to fruits to improve cosmetic features, such as

sheen or perceived depth of colour, to reduce deterioration by

suppressing water loss or to achieve modified atmosphere benefits.

Application of edible coating for food preservation has been divided

into following two subclasses

2.3.1 Fruits and vegetables

2.3.2 Other foods

2.3.1 Fruits and Vegetables

Fisk et al (2008) investigated calcium caseinate, chitosan,

PrimaFresh® 50-V, and SemperfreshTM edible coatings for their

potential to enhance the quality and extend the storage life of hardy

kiwifruit cv ‗Ananasnaya‘ .Coatings provided an attractive sheen to the

fruit surface and did not impair ripening. The consumer test indicated

that both coated and uncoated fruit were well liked.

Geraldine et al, (2008) evaluated effects of agar-agar based (1

percent) coatings incorporated with 0.2 percent chitosan and 0.2

percent acetic acid on minimally processed garlic cloves. Moisture loss

of coated garlic cloves was, on average, three times lower when

compared to the control samples. There was a marked increase in

color difference values for control cloves compared to the other

treatments. Filamentous fungus and aerobic mesophilic were inhibited

on garlic cloves coating incorporated with acetic acid + chitosan

antimicrobial compounds. During 6 days-storage, at 250C, the

filamentous fungus and yeasts count was maintained between 102

and 103 CFU g-1 for the coated garlic cloves and around 106 CFU g-1

for the control. The coatings provided significant reduction in clove


35

respiration. Coated garlic cloves, had a respiration rate (≈ 30 mg CO2

h-1 kg-1) halved compared to the non-coated garlic cloves.

Sothornvit and Rodsamran (2008) determined the effect of a

mango edible film and storage conditions on fresh mango quality and

shelf-life. A mango film provided a good oxygen barrier with sufficient

mechanical properties to wrap whole and minimally processed

mangoes. The film reduced weight loss and extended the ripening

period of whole fresh mangoes. The shelf-life of unwrapped minimally

processed mangoes kept in cellophane bags at room temperature

(300C) and cold storage (50C) were 2 and 4 days, respectively. When

the minimally processed mangoes were wrapped in a mango film and

kept in cellophane bags, the shelf-life was extended to 5 and 6 days,

when stored at 30 and 50C, respectively.

Tapia et al (2008) used alginate- (2% w/v) or gellan-based

(0.5% w/v) coating formulations on fresh-cut papaya pieces.

Formulations containing 2% (w/v) glycerol+1% ascorbic acid or 1%

glycerol+1% ascorbic acid exhibited slightly improved water barrier

properties for both types of coatings, as compared to the uncoated

samples. The incorporation of 0.025% (w/w) sunflower oil into the

alginate or the gellan-based formulations resulted in a 16% and 66%

increase in the WVR of the coated samples, respectively. In general,

coatings improved firmness of the fresh-cut product during the period

studied. Furthermore, the addition of ascorbic acid as antioxidant in

the coatings aided to preserve the natural ascorbic acid content of the

freshcut papaya, helping to maintain its nutritional quality

throughout storage. The gas barrier properties of the formulated

coatings were not modified to allow substantial changes on respiratory

rate and ethylene production of the coated papayas.

Albanese et al (2007) observed the effect of trehalose as an

edible coating on minimally processed Annurca apple slices during

cold storage. During storage at 60C the following parameters were

monitored: weight loss, colour and whitening index (WI)), firmness,


36

malic and ascorbic acids, polyphenol content, microstructure by

scanning electron microscopy (SEM) and microbial count. The results

showed that such a coating reduced the browning phenomena; in fact

the WI and hue values were significantly lower in coated samples than

untreated ones. Moreover, decreases in weight loss and in the

reduction of organic acids were observed in coated samples.

Chien et al (2007) observed the effect of treatment of sliced

mango with aqueous solutions of 0%, 0.5%, 1% or 2% chitosan and

then stored at 60C. Changes in the sensory qualities of taste, color

and water loss, were evaluated. A chitosan coating retarded water loss

and the drop in sensory quality, increasing the soluble solid content,

titratable acidity and ascorbic acid content. It also inhibited the

growth of microorganisms.

Chlebowska-Smigiel et al, (2007) studied the influence of the

pullulan and pullulan--protein edible coatings on the reduction of the

apples mass loss during the storage. Pullulan edible coating

significantly limited apples mass losses. Apples covered with coatings

showed lower mass losses than the ones uncovered. The smallest

mass losses were observed in apples covered with the coatings where

the pullulan to protein ratios were: 6:4 and 5:5. It was observed that

by adding protein to pullulan the coating stuck better to apples

surface. During the storage process the protein-containing layer was

less susceptible to crumbling and to peeling off.

Olivas et al, (2007) investigated effectiveness of edible coatings

made from alginate to preserve the quality of minimally processed

‗Gala‘ apples. Apple wedges were immersed in a calcium chloride

solution and subsequently coated with one of three different coating

formulations: alginate, alginate-acetylated monoglyceride-linoleic acid,

and alginate-butter-linoleic acid. Overall, it was found that alginate

coatings prolonged the shelf-life of cut apples without causing

anaerobic respiration. All coatings used minimized the weight loss

during storage, and apples with coatings containing acetylated


37

monoglyceride in particular remained the closest to original weight.

Firmness of coated apples remained practically constant regardless of

the type of coating, while control apples had a large decrease in

firmness during storage. Browning of apple slices was retarded in all

coated apples. A higher production of hexanol and trans-2-hexenal

was observed in coated apples containing butter and acetylated

monoglyceride.

Durango et al (2006) developed an edible antimicrobial coating

based on a starch–chitosan matrix to evaluate its effect on minimally

processed carrot by means of microbiological analyses. Coatings based

on 4% yam starch (w/w) + 2% glycerol (w/w) and coatings based on

4% yam starch (w/w) + 2% glycerol (w/w) + chitosan in 0.5% and

1.5% concentrations were prepared. Samples of minimally processed

carrot slices were immersed into these coatings. During storage, all

the samples had counting <100 CFU/g for Staphylococcus aureus and

<3 MPN/g for Escherichia coli. Starch + 0.5% chitosan coating

controlled the growth of mesophilic aerobes, yeasts and molds and

psychrotrophs during the first five days of storage, ultimately

presenting reductions of only 0.64, 0.11 and 0.16 log cycles,

respectively, compared to the control. Starch + 1.5% chitosan coated

samples showed reductions in mesophilic aerobes, mold and yeast

and psychrotrophic counting of 1.34, 2.50 and 1.30 log cycles,

respectively, compared to the control. The presence of 1.5% chitosan

in the coatings inhibited the growth of total coliforms and lactic acid

bacteria throughout the storage period.

Hernandez-Munoz et al, (2006) evaluated the effectivenss of 1

and 1.5 percent chitosan (CS) or chitosan combined with calcium

gluconate to extend the shelf life of Strawberries. No sign of fungal

decay was observed during the storage period for fruit coated with 1.5

percent CS (with or without the addition of CaGlu) or 1 percent CS +

0.5 percent CaGlu. By contrast, 12.5 percent of the strawberries

coated with 1 percent CS lacking calcium salt were infected after five


38

days of storage. The chitosan coating reduced respiration activity,

thus delaying ripening and the progress of fruit decay due to

senescence. Strawberries coated with 1.5 percent chitosan exhibited

less weight loss and reduced darkening than did those treated with 1

percent chitosan, independently of the presence or absence of CaGlu.

However, addition of calcium to the 1 percent chitosan solution

increased the firmness of the fruit.

Martınez-Romero et al (2006) used a novel edible coating

based on Aloe vera gel, as postharvest treatment to maintain sweet

cherry quality and safety. During cold storage, uncoated fruit showed

increases in respiration rate, rapid weight loss and colour changes,

accelerated softening and ripening, stem browning and increased

microbial populations, these processes being more intense during the

shelf life periods. On the contrary, sweet cherry treated with A. vera

gel significantly delayed the above parameters related to postharvest

quality losses, and storability could be extended. The sensory analyses

revealed beneficial effects in terms of delaying stem browning and

dehydration, maintenance of fruit visual aspect without any

detrimental effect on taste, aroma or flavours.

Matuska et al (2006) found that coating of whole strawberries

with selected edible (polysaccharide) films before osmotic processing

favor water removal and prevent solute uptake. Among tested

materials and coating procedures, double coating with a 0.5% sodium

alginate (SA) solution gave the best results in terms of a high water

loss (WL) to solid gain (SG) ratio (WL/SG). Single or double SA coating

inhibited leakage losses upon freeze/thawing of osmotically treated

strawberries.

Vargas et al, (2006) used edible coatings based on high

molecular weight chitosan combined with oleic acid to preserve quality

of cold-stored strawberries. Coatings had no significant effects on

acidity, pH and soluble solids contents of strawberries throughout

storage. In contrast, coatings slowed down changes in the mechanical


39

properties and slightly modified respiration rates of samples. Addition

of oleic acid not only enhanced chitosan antimicrobial activity but also

improved water vapour resistance of chitosan-coated samples.

Sensory analysis showed that coating application led to a significant

decrease in strawberry aroma and flavour, especially when the ratio

oleic acid:chitosan was high in the film.

Del-Valle et al (2005) investigated use of prickly pear cactus

mucilage (Opuntia ficus indica) as an edible coating to extend the

shelf-life of strawberries. Different methods for mucilage extraction

were tested in order to obtain the best coating. Edible films were

tested to determine their effects on colour, texture and sensory quality

of the fruit. From the results, it was concluded that the use of

mucilage coatings leads to increased strawberry shelf life.

Maftoonazad and Ramaswamy (2005) evaluated the effect of a

methyl cellulose-based coating on the respiration rate, color and

texture of avocados stored at room temperature. Coated avocados

demonstrated lower respiration rates, greener color and higher

firmness as compared with the uncoated control during the entire

storage. The appearance of brown spots and mesocarp discoloration

normally associated with fruit ripening were delayed in the coated

fruits.

Perez-Gago et al (2005) prepared edible composite coatings

from whey protein isolate (WPI), whey protein concentrate (WPC) or

hydroxypropyl methylcellulose (HPMC) as the hydrophilic phase, and

bees wax (BW) or carnauba wax (CarW) as the lipid phase and coated

on apple pieces. Results show that apple pieces coated with whey

protein-based coatings had higher L, and lower b, a and Browning

Index values than HPMC-based coated and uncoated apple pieces,

which indicate that whey proteins exert an antibrowning effect.

Coatings containing BW were more effective in decreasing enzymatic

browning than coatings containing CarW.


40

Tanada-Palmu et al (2005) studied the effect of different wheat

gluten-based coatings and films on refrigerated strawberry quality and

shelf life. The bilayer coating of wheat gluten and lipids (bees wax,

stearic and palmitic acids) had a significant effect on the retention of

firmness, reduced the weight loss and showed better results from the

physico-chemical analysis compared to the control fruit. All the

treatments with gluten film (except with the film pouch) also showed a

beneficial effect on firmness retention compared to the control fruit.

The gluten film (except the film wrap) seemed to be more promising for

controlling decay than the coatings. Sensory evaluation of the

strawberries showed that the gluten and the composite coatings

maintained the visual quality of the fruit during the storage time, and

the taste of the strawberries with the gluten coating was acceptable to

consumers. However, the appearance and taste of the bilayer-coated

fruit were unacceptable.

Ayranci and Tunc (2004) applied edible coatings of varying

composition on fresh apricots and green peppers. The main

components of the coating were methyl cellulose (MC) and

polyethylene glycol (PEG). Stearic acid (SA) and ascorbic acid (AA) or

citric acid (CA) were added to the coating formulation to control the

barrier properties toward water and oxygen. It was found that coatings

of any composition studied lower the water loss rate of fresh apricots

and green peppers. Coating formulation of MC–PEG–SA was the most

effective in reducing the water loss. Inclusion of AA or CA in the

coating formulation as antioxidants lowered the vitamin C loss.

Han et al, (2004) used chitosan-based edible coatings to extend

the shelf-life of strawberries and red raspberries stored at either 20C

and 88 percent relative humidity (RH) for 3 weeks or −230C up to 6

months. The coatings significantly decreased decay incidence and

weight loss, and delayed the change in color, pH and titratable acidity

of strawberries and red raspberries during cold storage. Coatings also


41

reduced drip loss and helped maintain textural quality of frozen

strawberries after thawing.

Plotto et al (2004) studied the effect of dipping Mango fruits for

30 seconds in 5 ppm chlorine dioxide, 2% calcium ascorbate and 0.5%

N -acetyl- L-cysteine (antioxidants), or coating solutions of 1%

carboxymethylcellulose (CMC) or CMC and 0.5% maltodextrin (CMM).

Coated fruit, and fruit treated with antioxidants stored at 5 °C

maintained good visual quality after three weeks as compared to

controls. L* value and hue angle were the highest for CMC-treated

fruit stored 21 days at 5 °C. When stored at 10 °C, visual quality of

the two controls was the lowest, but overall, none of the treatments

were acceptable after 14 days. CMC-treated fruit tended to be firmer

when stored at 5 °C after 11 days, but not at 10 °C. Taste panels did

not detect any difference between treatments.

Zhang et al (2004) studied the physiological and physical

changes in cucumber studied after treating with edible films coating

and ozone water. The study showed that the concentration of 4.2 mg

m–3 ozone and the C treatment (polyvinyl alcohol 134 (1%); chitosan

(1%); lithium chloride (0.5%); glacial acetic acid (2.5%); sodium

benzoate (0.05%)) with a combined coating inhibits respiration and

chlorophyll breakdown. Furthermore, it can also lower the soluble

solids content and inhibit the polyphenol oxidases (PPO) activity.

Bai et al, (2003) measured the gas permeabilities of shellac

wax, candelilla wax and shellac:carnauba wax applied to freshly

harvested and 5-month commercially stored ‗Delicious‘, ‗Fuji‘,

‗Braeburn‘ and ‗Granny Smith‘ apples. The shellac coating resulted in

maximum fruit gloss, lowest internal O2, highest CO2, and least loss of

flesh firmness for all of the varieties. The ‗Granny Smith‘ with shellac

had low internal O2 (< 2 kPa) with both freshly harvested and 5

month-stored apples, and the freshly-harvested ‗Braeburn‘ had high

internal CO2 (25 kPa). This excessive modification of internal gas

induced an abrupt rise of the respiratory quotient, prodigious


42

accumulation of ethanol in both ‗Braeburn‘ and ‗Granny Smith‘, and

flesh browning at the blossom end of ‗Braeburn‘.

Bai et al, (2003) used zein, to formulate alternative shiny

coatings by dissolving zein in aqueous alcohol with propylene glycol

(PG). Gloss levels on ‗Gala‘ apple surfaces varied due to zein and PG

content in coating formulations from that of controls to levels

observed for shellac-coated fruit. At least 4 percent (by weight) PG was

necessary for adequate gloss. However, increasing levels of both

compounds resulted in increased gloss. Internal CO2 and O2 in zein-

coated ‗Gala‘ fruit ranged 4-/11 and 19-/6 kPa, respectively, by

increasing zein content in the coatings. An optimum formulation with

10 percent zein and 10 percent PG was developed, applied to ‗Gala‘

apple, and was found to maintain overall fruit quality comparable to a

commercial shellac coating.

Lee et al (2003) investigated effect of edible coatings in

combination with antibrowning agents on minimally processed apple

slices. Initial respiration rate showed a decrease by 5% and 20% in

carrageenan (0.5 g/100 mL)-coated and whey protein concentrate (5

g/100 mL) coated apples, respectively, at 250C. Edible coatings in

combination with antibrowning agents effectively prolonged the shelf-

life of minimally processed apple slices by 2 week when stored in

packed trays at 30C. Addition of CaCl2 (1 g/100 mL) significantly

inhibited the loss of firmness.

Yaman and Bayoindirli (2002) studied the effects of an edible

coating, i.e. SemperfreshTM and cold storage on shelf-life and quality

of cherries. It was demonstrated that SemperfreshTM was effective to

reduce the weight loss and increase firmness, ascorbic acid content,

titratable acidity and skin color of cherries during storage time.

However, soluble solid content and sugar content were not affected by

coating. The results of this study suggest that SemperfreshTM

increased the shelf-life of the cherries by 21% at ambient conditions


43

by 26% at cold storage conditions without perceptible losses in

quality.

Chen and Nussinovitch (2000) introduced Locust bean gum

(LBG) or guar gum, into traditional wax formulations of two easy-

peeler citrus fruit cultivars: Nova and Michal. Their performance was

analyzed and compared to inclusion of the non-gelling xanthan gum

in a similar formulation. Both galactomannans reduced weight loss of

the fruit during respiration in a manner similar to a wax-based

coating without gum. Inclusion of galactomannan in the formulation

did not change the gloss of the coated easy-peelers, even though

xanthan is known to produce better gloss.

Baldwin et al, (1999) tested two types of fruit coatings, one

coating was polysaccharide-based while the other had carnauba wax

as the main ingredient, for their effect on external and internal mango

fruit atmospheres and quality factors. Polysaccharide coatings are less

permeable to respiratory gases, such as O2, and more permeable to

water vapor compared to carnauba wax. Both coatings created

modified atmospheres, reduced decay, and improved appearance by

imparting a subtle shine; but only the polysaccharide coating delayed

ripening and increased concentrations of flavor volatiles. The

carnauba wax coating significantly reduced water loss compared to

uncoated and polysaccharide-coating treatments.


44

Table 2.6 Review on Preservation of Fruits and Vegetables by

Using Edible Film/Coating

Sr

No.


1 Fisk et al 2008 Coatings provided an attractive sheen

to the hardy kiwi fruit surface and did

not impair ripening. The consumer

test indicated that both coated and

uncoated fruit were well liked.

2 Geraldine et

al

2008 Filamentous fungus and aerobic

mesophilic inhibits on garlic cloves

coated with agar agar base film

incorporated with acetic acid and

chitosan antimicrobial compounds.

3 Sothornvit

and

Rodsamran

2008 A mango film provides a good oxygen

barrier with sufficient mechanical

properties to wrap whole and

minimally processed mangoes. The

film reduces weight loss and extend

the ripening period of whole fresh

mangoes.

4 Tapia et al 2008 The alginate and gellan based coatings

improved firmness of the fresh-cut

papaya and the addition of ascorbic

acid as antioxidant in the coatings

aided to preserve the natural ascorbic

acid content of the fresh-cut papaya,

helping to maintain its nutritional

quality throughout storage.

5 Albanese et

al

2007 In Trehalose coated apple slices WI

and hue values were significantly

lower in coated samples than

untreated ones along with, decrease in

weight loss and in the reduction of

organic acids.

6 Chien et al 2007 A chitosan coating on sliced mango

retarded water loss and the drop in

sensory quality, increasing the soluble

solid content, titratable acidity and

ascorbic acid content


45

7 Chlebowska-

Smigiel et al

2007 Pullulan edible coating significantly

limits apples mass losses.

8 Olivas et al 2007 Different alginate coatings used

minimize the weight loss during

storage and apples with coatings

containing acetylated monoglyceride

in particular remained the closest to

original weight.

9 Durango et

al

2006 The use of edible antimicrobial yam

starch and chitosan coating is a viable

alternative for controlling

microbiological growth in minimally

processed carrot.

10 Hernandez-

Munoz et al

2006 The chitosan coating reduces

respiration activity, thus delaying

ripening and the progress of fruit

decay due to senescence in

strawberries & addition of calcium to

the chitosan solution increases the

firmness of the fruit.

11 Martınez-

Romero et al

2006 Sweet cherry treated with aloe vera gel

significantly delay postharvest quality

losses and extend the storability.

12 Matuska et

al

2006 Coating of whole strawberries with

selected edible (polysaccharide) films

before osmotic processing favor water

removal and prevent solute uptake

13 Vargas et al 2006 Addition of oleic acid not only

enhanced chitosan antimicrobial

activity but also improved water

vapour resistance of chitosan-coated

samples.

14 Del-Valle et

al

2005 The use of cactus mucilage coatings

leads to increased strawberry shelflife.

15 Maftoonazad

and

Ramaswamy

2005 Avocados coated with methyl cellulose

based coating demonstrates lower

respiration rates, greener color and

higher firmness as compared with the

uncoated control during the entire

storage.


46

16 Perez-Gago

et al

2005 Apple pieces coated with whey

protein-based coatings had higher L*,

and lower b*, a*, and BI-values than

HPMC-based coated and uncoated

apple pieces.

17 Tanada-

Palmu and

Grosso

2005 The bilayer coating of wheat gluten

and lipids has a significant effect on

the retention of firmness, reduce the

weight loss and show better results

from the physico-chemical analysis

compared to the control fruit.

18 Ayranci and

Tunc

2004 Methyl cellulose based coatings lower

the water loss rate of fresh apricots

and green peppers and inclusion of

Ascorbic acid or Citric Acid in the

coating formulation as antioxidants

lower the vitamin C loss.

19 Han et al 2004 The coatings significantly decrease

decay incidence and weight loss, and

delay the change in color, pH and

titratable acidity of strawberries and

red raspberries during cold storage.

20 Plotto et al 2004 Coated mango fruit, and fruit treated

with antioxidants stored at 5 °C

maintained good visual quality after

three weeks as compared to controls.

CMC-treated fruit tended to be firmer

when stored at 5 °C after 11 days, but

not at 10 °C

21 Zhang et al 2004 Combined coating inhibits respiration

and chlorophyll breakdown in case of

cucumber. It also lower the soluble

solids content and inhibit the

polyphenol oxidases (PPO) activity.

22 Bai et al 2003 The shellac coating results in

maximum fruit gloss, lowest internal

O2, highest CO2, and least loss of flesh

firmness for all of the varieties of

apples studied.


47

23 Bai et a 2003 Gloss levels on ‗Gala‘ apple surfaces

varies due to zein and propylene glycol

content in coating formulations from

that of controls to levels observed for

shellac-coated fruit.

24 Lee et al 2003 Edible coatings in combination with

antibrowning agents effectively

prolonged the shelf-life of minimally

processed apple slices by 2 week when

stored in packed trays at 30C

25 Yaman and

Bayoindirli

2002 SemperfreshTM was effective to

reduce the weight loss and increase

firmness, ascorbic acid content,

titratable acidity and skin color of

cherries during storage time. However,

soluble solid content and sugar

content were not affected by coating.

26 Chen and

Nussinovitch

2000 Addition of galctomannans in

traditional wax based formulation of

citrus fruits reduced weight loss of the

fruit during respiration in a manner

similar to a wax-based coating without

gum.

27 Baldwin et

al

1999 Polysaccharide coatings are less

permeable to respiratory gases, such

as O2, and more permeable to water

vapor compared to carnauba wax.

28 Li and Barth 1998 Edible coatings improve carotene

retention and retard surface whitening

in lightly processed carrots during

postharvest storage.

Li and Barth (1998) evaluated the effects of two edible coatings

(EC) of varying pH (2.7 and 4.6) on carotene retention and other

physiological changes in lightly-processed (LP) carrots during storage.

Results showed that carotene retention was 15 percent greater in the

EC treatments versus control treatment throughout the 28 days.

Samples treated with the lower pH EC had the highest CO2 and lowest

O2 concentrations in the headspace. Whiteness index (WI) scores were


48

significantly lower in both coated samples. Ethylene production was

greatest in carrots treated with the lower pH coating on removal from

sealed bags to air after each storage period. ECs improved carotene

retention and retarded surface whitening in LP carrots during

postharvest storage. The research related to preservation of fruits and

vegetables by using edible film/coating can be summarized as shown

in Table 2.6

2.3.2 Other foods

Ghasemzadeh, et al (2008) investigated effect of three different

edible coating materials including Pectin, Plant Gum and Starch on

two varieties of raisin, Thompson seedless and Shahani. During period

of storage, chemical, microbiological and sensory properties were

evaluated. The data indicated that performance of pectin film was

better than gum and starch coatings. Microbiological evaluation

showed that the microbial count decreased significantly in both PDA

and Osmophilic Agar media during storage period (P<0.05). The

results of sensory evaluation showed that the colour and texture of

Thompson seedless variety coated with pectin were the best, while in

the term of flavour, samples covered with gum proved to be the best.

In the case of Shahani variety, the samples coated with pectin had

better colour, texture and flavor, significantly (P<0.05). The scanning

electron microscopy evaluation of coated samples showed that the

pectin film was the most even among all of the other coating

materials.

Oses et al, (2008) investigated the capability of Whey protein

isolate (WPI) films for delaying lipid oxidation in vegetable oil, as an

example of a food rich in PUFA. Results obtained showed that WPI

films delayed the rancidity in vegetable oil. Films with sorbitol were

more effective than films with glycerol, providing a protection as

effective as aluminum foil. The thickest films with the lowest

plasticizer content provided the greatest protection against lipid


49

oxidation. Plasticizer content affected film protection much more

intensively than thickness. WPI films presented a more effective

protection at 50 percent RH than at 75 percent RH.

Sathivel et al (2007) determined the effect of chitosan (CH1,

1% w/w solution) glazing on the quality of skinless pink salmon fillets

after eight months frozen storage. Fillets glazed with CH1 solution

exhibited significantly (p < 0.05) higher yield and thaw yield than the

lactic acid-glazed (LA) and distilled water-glazed (DW) fillets, although

these fillets all had similar moisture content after thawing. Chitosan,

DW, and LA glazing delayed lipid oxidation in skinless pink salmon

fillets after eight months frozen storage.

Bravin et al (2006) evaluated the effectiveness of edible coating

in controlling moisture transfer in moisture-sensitive products by

coating crackers, a low aw-type cereal food. Spread film gave better

water vapor barrier and mechanical properties than sprayed film. High

atomization pressure and thickness increased film WVP. Atomization

pressure of 2 bar and film thickness of 30 micron were identified as

optimum for the application of edible coating to bakery products.

Coated and uncoated crackers were stored at 65%, 75% and 85%

relative humidity. Coated crackers had longer shelf-life and higher

water vapor transmission than reference at all storage conditions.

Kang et al 2005 studied physicochemical, microbiological and

sensorial qualities of cooked pork patty coated with pectin-based

material containing green tea leaf extract powder. Cooked pork patties

were separated into three groups; uncoated control (C), coated with

pectin-based materials (CP), and coated with pectin-based materials

containing 0.5% green tea powder (CGP). The prepared patties were

irradiated at 0 and 3kGy using cobalt-60 gamma rays. Lipid oxidation,

free radical scavenging effects, moisture content, total plate count,

and sensory properties were evaluated during storage for 14 days at

10 °C. Lipid oxidation decreased (p<0.05) and radical scavenging

(p<0.05) increased in the pork patties in CGP or CP relative to those of


50

the controls when vacuum packaged. Coated patties contained higher

moisture contents than the controls in both air- and vacuum

packaging. The numbers of total aerobic bacteria were significantly

reduced by the coating treatments as well as by irradiation. No

difference were detected in sensory characteristics due to gamma

irradiation or coating treatments.

Albert and Mittal (2002) Compared eleven hydrocolloid

materials including gelatine, gellan gum, k-carrageenan-konjac-blend,

locust bean gum, methyl cellulose (MC), microcrystalline cellulose,

pectin (three types), sodium caseinate, soy protein isolate (SPI), vital

wheat gluten and whey protein isolate (WPI) for their film forming

ability, suitability for fried foods, and water and fat transfer

properties. Gelatin, wheat gluten and sodium caseinate were not

suitable in single material coating. The SPI, WPI and MC were the best

materials for coating to reduce fat uptake during frying. SPI/MC and

SPI/WPI mixed coatings provided the highest index value (reduction in

fat uptake/decrease of water loss), and reduced the fat uptake up to

99.8 percent.

Rayner et al, (2000) developed a soy protein film coating to

reduce fat transfer in deep-fried foods during frying. Soy protein

isolate solutions (10 percent SPI) with 0.05 percent gellan gum as

plasticizer cooled after being held at 80°C for 20min provided suitable

films. There was a significant fat reduction (55.12±6.03 percent db)

between fried uncoated and coated discs of doughnut mix. The same

films were used on potato fries. Some panelists observed a slight

difference between the coated and uncoated fries but many preferred

the coated fries over the uncoated ones. Penetration test on potato

fries showed no significant difference between the texture of coated

(SPI with gellan gum) and the uncoated fried samples. The research

related to preservation of other foods with edible film/coating can be

summarized as shown in Table 2.7


51

Table 2.7 Review on Preservation of Other Foods with Edible

Film/Coating

Sr

No.


1 Ghasemzadeh,

et al

2008 For Thompson seedless raisins

performance of pectin film was

better than gum and starch

coatings. In case of Shahani variety,

the samples coated with pectin had

significantly (P<0.05) better colour,

texture and flavor,

2 Oses et al 2008 Whey Protein Isolate films delays the

rancidity in vegetable oil

3 Sathivel et al 2007 skinless pink salmon fillets glazed

with chitosan solution exhibited

significantly (p < 0.05) higher yield

and thaw yield than the lactic acid-

glazed (LA) and distilled water-glazed

(DW) fillets,

4 Bravin et al 2006 Evaluated the effectiveness of edible

coating in controlling moisture

transfer in moisture-sensitive

products by coating crackers, a low

aw-type cereal food

5 Kang et al 2005 Lipid oxidation decreased (p<0.05)

and radical scavenging (p<0.05)

increased in the pork patties coated

with pectin based edible coating

relative to those of the controls when

vacuum packaged.

6 Albert and

Mittal

2002 The Soy protein isolate, Whey

protein isolate and methyl cellulose

are the best materials for coating to

reduce fat uptake during frying.

7 Rayner et al 2000 In a doughnut mix coated with soy

protein isolate film, significant fat

reduction takes place between fried

coated and uncoated samples.


52

2.4 Edible Films as Means of Fortification

Jongjareonrak et al (2008) investigated anti oxidative activity

and properties of fish skin gelatin-based films incorporated with BHT

(butylated-hydroxy-toluene) or a-tocopherol. Changes in FTIR spectra

of fish skin gelatin films were observed when BHT and a-tocopherol at

a level of 200 ppm was incorporated, suggesting some interaction

occurred between gelatin molecules and the antioxidants added. Anti

oxidative activity of fish skin gelatin films incorporated with BHT and

a-tocopherol increased markedly with increasing storage time as

indicated by the increase in DPPH radical scavenging activity. Films

without and with BHT and a-tocopherol incorporated showed a

preventive effect on lard oxidation as evidenced by the retardation of

thiobarbituric acid reactive substances (TBARS) and peroxide

formation.

Sivarooban et al (2008) evaluated the physical and

antimicrobial properties of soy protein isolate (SPI) films containing

grape seed extract (GSE 1% w/w), nisin (10,000 IU/g),

ethylenediaminetetraacetic acid (EDTA 0.16 % w/w), and their

combinations. The SPI film incorporated with the combined GSE,

nisin, and EDTA demonstrated the greatest inhibitory activity against

Listeria monocytogenes. Furthermore, the results showed that the SPI

film containing GSE 1%, nisin 10,000 IU/g, and EDTA 0.16 % was

able to reduce Listeria monocytogenes populations by 2.9 log CFU/ml,

while the population of E. coli O157:H7 and Salmonella typhimurium

were reduced by 1.8 and 0.6 log CFU/ml, respectively.

Rojas-Grau (2007) formulated alginate (2% w/v) and gellan

(0.5% w/v)-based edible coatings to study the effect of glycerol (G)

and anti browning agents (N-acetylcysteine and glutathione) on water

vapor resistance (WVR). Selected formulations obtained by a response

surface analysis were 1.5% G, 1% N-acetylcysteine and 0.63% G, 1%

N-acetylcysteine for alginate and gellan, respectively. The addition of

sunflower oil with essential fatty acids (ω 3 and ω 6) at 0.025%,


53

0.05%, and 0.125% w/v concentrations was also investigated in an

attempt to improve the barrier properties of the alginate and gellan

coatings for fresh-cut apples. The WVR increased significantly from

15.70 and 14.60 s/cm to 19.2 and 27.6 s/cm for alginate and gellan

coatings with sunflower oil, respectively, in comparison with control.

The addition of sunflower oil in gellan was more effective than in

alginate to increase the WVR of coated apples. Alginate and gellan-

based coatings proved to be good carriers for anti browning agents.

Salleh et al (2007) developed edible packaging based on wheat

starch incorporated with lauric acid and chitosan as antimicrobial

agents. The antimicrobial effect was tested on B. substilis and E. coli.

Inhibition of bacterial growth was examined using two methods, i.e.

zone of inhibition test on solid media and liquid culture test (optical

density measurements). It was observed that only antimicrobial films

exhibited inhibitory zones. Interestingly, a wide clear zone on solid

media was observed for B. substilis growth inhibition whereas

inhibition for E. coli was only revealed underneath the film discs.

From the liquid culture test, the antimicrobial films clearly

demonstrated a more effective inhibition against B. substilis than E.

coli.

Sanjurjo et al (2006) studied the antimicrobial activity of nisin

supported in edible films prepared with suspensions of tapioca starch

containing glycerol. Films were prepared by casting the systems after

gelatinization. Results obtained showed that nisin supported in

starch-based films is active and that the film is a useful barrier to

further product contamination. Gradual release of the antimicrobial

from the edible film can also help to preclude microorganism

proliferation better than nisin directly added because it seems to

counterbalance, at least partially, the inactivation of nisin.

Pranoto et al (2005) compared antimicrobial effect of chitosan

edible film incorporating garlic oil (GO) with conventional food

preservative potassium sorbate (PS) and bacteriocin nisin (N) at


54

various concentrations. Incorporation of GO up to levels at least 100

ml/g, PS at 100 mg/g or N at 51,000 IU/g of chitosan were found to

have antimicrobial activity against S. aureus, L. monocytogenes, and

B. cereus. At these levels, the films were physically acceptable in term

of appearance, mechanical and physical properties. GO components

did not affect the physical and mechanical properties of chitosan films

as it did not have any interaction with the functional groups of

chitosan as measured by FTIR.

Shrestha et al (2003) investigated the technical feasibility of

adding folic acid on to rice and coating with edible polymers. A

concentrated premix of rice was prepared in a rotating coating pan by

spraying first with folic acid solution, and then with polymer solutions

and drying. The fortified rice premixes were evaluated for washing and

cooking losses. The loss of folic acid in washing was lowest in rice

premixes coated with ethyl cellulose followed by pectin, composite

mixtures of locust bean and other coating materials with highest loss

in gum arabic coated rice. No edible polymer could satisfactorily retain

folic acid during boiling in excess water. Edible polymers failed to

mask the yellow color of folic acid and additional masking agent was

needed. The premixes had a higher water uptake ratio than raw milled

rice had. Triangle tests did not show any significant difference

between the sensory qualities of cooked fortified rice and raw milled

rice.

Baldwin et al (1996) found that a cellulose-based edible

coating, as carrier of antioxidants, acidulants and preservatives

prolonged the storage life of cut apple and potato by about 1 week

when stored in over wrapped trays at 4°C. Storage of coated apple

discs in vacuum-packed trays reduced weight loss and browning

compared to over wrapped tray storage. Ascorbic acid delayed

browning more effectively when applied in an edible coating than in an

aqueous solution. Adjustment of coating pH to 2.5 gave optimal

control of browning and microbial populations.


55

The research related to edible films as means of fortification can be

summarized as shown in Table 2.8

Table 2.8 Review on Edible Films as Means of Fortification

Sr

No.


1 Jongjareonraka

et al 2008 Anti oxidative activity of gelatin

films incorporated with BHT and a-tocopherol increases markedly with

increasing storage time and films with BHT and a-tocopherol incorporated show a preventive

effect on lard oxidation.

2 Sivarooban et al

2008 The soy protein isolate film incorporated with the combined grape seed extract, nisin, and EDTA

exhibits the greatest inhibitory activity against Listeria monocytogenes.

3 Rojas-Grau 2007 Alginate and gellan-based coatings

are good carriers for anti browning agents.

4 Salleh et al 2007 Wheat starch films incorporated with lauric acid and chitosan shows

antimicrobial activity against B. substilis and E.coli

5 Sanjurjo et al 2006 Nisin supported in starch-based

films is active and the film is a useful barrier to further product contamination

6 Pranoto et al 2005 Chitosan based edible film

incorporated with garlic oil have antimicrobial activity against S.aureus, L.monocytogens and B.cereus.

7 Shrestha et al 2003 The loss of folic acid in washing is lowest in rice premixes coated with

ethyl cellulose followed by others while no edible polymer can satisfactorily retain folic acid during

boiling in excess water

8 Baldwin et al 1996 Cellulose-based edible coating, as carrier of antioxidants, acidulants and preservatives prolong the

storage life of cut apple and potato

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