Ozdemir e Floros, 2008

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Optimization of edible whey protein films containing preservativesfor water vapor permeability, water solubility

and sensory characteristics

M. Ozdemir a,*, John D. Floros b

a Department of Chemical Engineering, Section of Food Technology, Gebze Institute of Technology, P.O. Box 141, 41400 Gebze, Kocaeli, Turkeyb Department of Food Science, Pennsylvania State University, 111 Borland Laboratory, University Park, PA 16802, USA

Received 8 August 2007; received in revised form 20 September 2007; accepted 22 September 2007Available online 1 October 2007

Abstract

The effect of protein, sorbitol, beeswax and potassium sorbate concentrations in whey protein films on their water vapor permeability,water solubility and organoleptic properties was investigated using mixture response surface methods. All factors including proteinsorbitol, beeswax and potassium sorbate influenced water vapor permeability and water solubility of the films. Beeswax was the mostimportant factor influencing the stickiness and appearance of the films. Amount of protein (5065%, w/w) had no effect on stickinessand appearance, while the amount of sorbitol (3550%, w/w) in the films had no influence on appearance. Mixture proportions ofprotein = 0.53, sorbitol = 0.38, beeswax = 0.08 and potassium sorbate = 0.01 would yield an edible film with minimum stickiness, watervapor permeability 6 9 g mm m2 h1 kPa1, water solubilityP 39% and appearance scoreP 80.2007 Elsevier Ltd. All rights reserved.

Keywords: Edible films; Whey protein; Potassium sorbate; Response surface; Water vapor permeability; Solubility; Sensory

1. Introduction

In recent years, a great deal of research has been dedi-cated to develop active packages through the use of ediblefilms and coatings. Edible films and coatings are usuallyused to control moisture transfer, limit gas transport,retard oil and fat migration, prevent solute or flavorabsorption, carry food additives such as antimicrobial

agents and antioxidants, and improve structural integrityof foods. The properties of edible films and coatingscomposed of hydrocolloids, lipids and proteins have beencomprehensively reviewed (Baldwin, Nisperos-Carriedo,& Baker, 1995; Debeaufort, Quezada-Gallo, & Voilley,1998; Krochta & De Mulder-Johnston, 1997; Miller &Krochta, 1997). Functional properties and potential appli-cations of edible films and coatings made of milk proteins

are well known (Chen, 1995; McHugh & Krochta, 1994aRhim & Ng, 2007).

Whey proteins have exceptional nutritional value andfunctional properties (Huffman, 1996; Kinsella, 1984). Inaddition, liquid whey is produced in large quantities, andits annual production increases continuously (Banerjee &Chen, 1995). The formation of edible films and coatingsfrom whey proteins can increase the utilization of whey

improve the nutritional value of foods and prolong shelflife.

Ozdemir and Floros (2001)produced antimicrobial filmsfrom commercial whey protein isolate and investigated therelease mechanism of potassium sorbate from the filmsOzdemir and Floros (2003) also studied the effect of filmcomposition on potassium sorbate diffusion in wheyprotein films using mixture response surface methodologyIncreasing the relative amounts of protein and beeswax inthe films decreased potassium sorbate diffusivity, whileincreasing the relative amounts of plasticizer and initia

0260-8774/$ - see front matter 2007 Elsevier Ltd. All rights reserved.

doi:10.1016/j.jfoodeng.2007.09.028

* Corresponding author. Tel.: +90 262 605 3290; fax: +90 262 653 8490.E-mail address:[email protected] (M. Ozdemir).

www.elsevier.com/locate/jfoodeng

Available online at www.sciencedirect.com

Journal of Food Engineering 86 (2008) 215224
mailto:[email protected]:[email protected]


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potassium sorbate in the films increased the diffusion ofpotassium sorbate.McHugh, Aujard, and Krochta (1994)determined the effects of plasticizers, pH and relativehumidity on their water vapor permeability. Plasticizersincreased water vapor permeability, and this effect wasmore pronounced as the plasticizer concentration in whey

protein films increased. At constant temperature and rela-tive humidity, high water vapor permeability values wereobtained at low pH (


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However, either first or second order models can be used toapproximate the true functions:

Yn bn0X4

i1

bnixi 2

Yn bn0X

4

i1 bnixiX

4

i1 bniix

2

i X

3

i1

X4

ji1 bnijxixj 3

where Yn is the expected response, bn0 is the value of theresponse at the standard reference mixture according toCox reference model (Cox, 1971), and bni, bnii and bnijare constant coefficients.

2.2. Statistical analysis

Cox reference model was fitted by multiple regressionanalysis using Modde software (version 4.0, Umetri AB,Umea, Sweden) to determine the coefficients (bs). Model

diagnostics were done by generating normal probabilityplot, and the plots of residual versus predicted values andobserved versus predicted values. Trace and contour plotsfor responses were created with Design-Expert software(version 5.0, Stat-Ease Inc., Minneapolis, MN). The traceplot provides silhouette views of the response surface. Inother words, the trace plot shows the effects of changingeach component from the reference blend to the vertex.Contour plots are used to see graphically how theresponses change with respect to the factors and they showgraphical representation of the response surface.

2.3. Materials

BiPRO whey protein isolate (WPI) was supplied byDavisco Foods International (Le Sueur, MN). WPI waslactose free with 99.5% protein. Sorbitol and potassiumsorbate were obtained from Sigma Chemical (St. Louis,MO). Beeswax (bleached and white) was purchased fromAldrich Chemical Company (Milwaukee, WI).

2.4. Film formation and film casting

Films were formed with the method described byOzd-emir and Floros (2001, 2003). Aqueous solutions of 10%(w/w) WPI were prepared by stirring dry WPI powder indistilled water until the WPI was completely dissolved.Solutions were placed in a water bath (model MW-1120A-1, Blue M Electric, Blue Island, IL) at 90 C and keptthere for 30 min to denature the protein. Solutions werethen cooled to room temperature, and various amountsof sorbitol (3550%, w/w) were added to plasticize thefilms.

For the manufacturing of lipid-containing films, WPI/sorbitol solutions were reheated to 85 C, and appropriateamounts of beeswax (015%, w/w) were melted in these hotWPI/sorbitol solutions. The mixture was thoroughly

homogenized in a homogenizer (type PT10/35, Brinkmann

Instruments Company, Westbury, NY) equipped with aprobe (model PTA 35/2, Brinkmann Instruments Com-pany, Westbury, NY) at 15,000 rpm for 2.5 min. Afterhomogenization, solutions were rapidly cooled to roomtemperature by placing them in an ice bath to prevent fur-ther denaturation of protein (Shellhammer & Krochta

1997).Various amounts (010%, w/w) of potassium sorbatewere finally added and mixed to form antimicrobial filmsAll solutions were degassed using a vacuum pump (GeneraElectric, Fort Wayne, IN) at room temperature to removeair bubbles in solutions.

Films were casted by pipetting 10 mL of solution onrimmed and smooth low density polyethylene (LDPE) cast-ing plates (Texaco Inc., White Plains, NY) with innerdiameters of 10.5 cm. Solutions were spread evenly with abent L-shaped glass rod, and they were allowed to dryfor 24 h at 50 5% relative humidity (RH) and 25 2 Cin a controlled temperature and humidity room. After24 h, dried films were peeled intact from the casting plates

2.5. Film conditioning

All films were conditioned in a controlled temperatureand humidity storage room at 50 5% RH and 25 2 C for 48 h prior to tests.

2.6. Water vapor permeability

Water vapor permeability (WVP) of the films was mea-sured gravimetrically according to the WVP correction

method as described by McHugh, Avena-Bustillos, andKrochta (1993), a modification of ASTM E96 (ASTM1997). This modification is needed since ASTM E96method is designed to determine WVP of synthetic hydro-phobic films. A plastic desiccator cabinet equipped with afan capable of operating at variable speeds (Tuthill PumpCorp., Concord, CA) was placed into a controlledtemperature and humidity room at 50 2% RH and25 0.5 C. A digital hygrometer and thermometer(Fisher Scientific, Inc., Fair Lawn, NJ) was also placedinside the cabinet to monitor the relative humidity andtemperature more precisely. Air speeds inside the cabinet

were measured using an anemometer (Davis InstrumentsHayward, CA). The fan speed was set to 182 m min1 toprevent stagnant air layer formation outside test cupsand to achieve uniform relative humidity throughout thecabinet.

Circular cups with internal diameter of 10.5 cm anddepth of 2.1 cm were used to test film WVP. Cup wallsare sufficiently thick (0.55 0.03 mm) to prevent watervapor transfer through the walls. Three replicates of eachfilm were tested. Films free of any defects such as pinholesair bubbles and cracks were used for WVP determinationsThe thicknesses of three replicates of each film formulationwere measured with an electronic digital micrometer (Max-

Cal Inc., Japan) at six random locations on the film to the

M. Ozdemir, J.D. Floros/ Journal of Food Engineering 86 (2008) 215224 217


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nearest 0.001 mm. Average film thickness was 0.181 0.028 mm.

Distilled water (20 mL) was placed in the bottoms of thetest cups. Test films cut circular with a razor knife weresealed on the cups using a waterproof adhesive. The lipidside of the films faced the high relative humidity environ-

ment (toward the inner of the test cup) and their proteinrich sides faced the room atmosphere (McHugh &Krochta, 1994c). When a thin film is coated on a foodsurface, it is desired that the lipid side of the film has tobe in contact with high relative humidity environment sothat the coating goes to a minimal interaction with waterand thus, the food is protected better from the negativeeffects of water. A thin coating of high vacuum siliconesealant (Beckman Instruments, Inc., Palo Alto, CA) wasapplied around the cup circumference to prevent watervapor transfer through the sealant area. Average stagnantair gaps between the water level in the cup and the innerfilm surface was measured both before and after eachexperiment (McHugh & Krochta, 1994c). The mean airgap between the water level in the cup and the inner filmsurface after the test was 10 2 mm. After the test began,steady state was attained in almost 2 h. Cups were thenperiodically weighed for 24 h. The weight loss of the testcups was measured to the nearest 0.0001 g.

Water vapor transmission rates (WVTR) of films atsteady state were determined from the slope of weight lossversus time plots using Eq. (4). Linear regression coeffi-cients (R2) were greater than 0.99 for all plots. The areaof film exposed in the test cup was 86.5 cm2.

WVTR Slope

Film area 4

The corrected water vapor partial pressure at the filminner surface (p2) for hydrophilic films can be calculatedfrom the following equation (McHugh et al., 1993):

p2 pT pT p1 expWVTRRT Dz=pTD 5

where pT is the total pressure (kPa), p1 is the water vaporpartial pressure at the solution surface (kPa), R is the idealgas law constant (8.314 kJ kg mol1 K1),Tis the absolutetemperature (K),D is the diffusivity of water through air at25 C (m2 h1) and Dz is the mean stagnant air gap (m)

inside the cup.Permeance is equal to the WVTR divided by the watervapor partial pressure gradient across the film, as givenby Eq.(6):

Permeance WVTR

p2 p3 6

where p3 is the water vapor partial pressure at the filmouter surface (kPa).

The corrected water vapor permeability is calculated bymultiplying the permeance corrected by Eq. (6)and aver-age film thickness, as shown in Eq. (7):

Permeability PermeanceThickness 7

For each experiment, relative humidity values under thefilm surface were corrected by using the proceduredescribed byMcHugh et al. (1993).

2.7. Film solubility (total soluble matter)

A method modified from Stuchell and Krochta (1994)was used to determine the solubility of films in water. Filmswere cut into 20 mm 20 mm pieces and dried at 70 Cand 96 kPa in a vacuum oven for 24 h. After drying, filmswere weighed to the nearest 0.0001 g for the determinationof the initial dry weights of films. Films were individuallyplaced into 20 mL of distilled water in 50 mL screw-topcentrifuge tubes. The tubes were capped and placed in ashaking water bath at 25 0.1 C for 24 h. Film pieceswere then taken out and dried at 70 C and 96 kPa in avacuum oven for 24 h to determine the final dry weightsof films. Three replicates of each film were done. Percenttotal soluble matter was calculated from the initial andfinal dry weights of films and reported on dry weight basis.

2.8. Sensory analysis

A sensory panel consisting of 12 members was carriedout. All panel members were trained by the open discussionmethod prior to sensory tests. Stickiness and appearance ofthe film samples were selected as sensory attributes to beincluded in the sensory testing. Stickiness and appearanceare two critical sensory attributes providing crucial infor-mation on the applicability of edible films and coatingson food surfaces as protective layers.

Descriptive analysis (Stone & Sidel, 1993) was used toevaluate selected sensory attributes of the films. Sensoryscores were recorded based on line marking scales whereeach panelist placed a mark on a 150 mm line to indicatethe intensity of each attribute. The endpoints were labeledas not sticky/extremely sticky and dislike extremely/likeextremely for stickiness and appearance, respectively. Thenumerical score for each attribute was determined by mea-suring the distance in mm with a ruler from the left-handside of the 150 mm line scale to the point that each panelistplaced a mark that best described the attribute. All sampleswere randomly selected and presented to judges. Panelists

were requested to chew the films in their mouths and eval-uate if the films are sticky. Cups with water were providedfor panelists to use during the test to minimize the residualstickiness effect of the films in the mouth. Appearance wasevaluated by visual observation. Sensory analysis wasconducted under controlled laboratory conditions in indi-vidually partitioned booths.

3. Results and discussion

3.1. Model development

Experimental points in terms of actual values and exper-

imental data are shown in Table 1. The comparison of the

218 M. Ozdemir, J.D. Floros / Journal of Food Engineering 86 (2008) 215224


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linear and quadratic models developed for WS and AP(Table 2) revealed that only linear models were significant(P6 0.01). These models did not show any significant lack

of fit (P6 0.05). Although the linear models developed forWVP and ST were significant at P6 0.01, they exhibitedsignificant lack of fit (P6 0.05). The quadratic models

Table 1Experimental design and experimental data

Samplenumbera

Whey proteinisolate(%, w/w)

Sorbitol(%, w/w)

Beeswax(%, w/w)

Potassiumsorbate(%, w/w)

Water vaporpermeability(g mm m2 h1 kPa1)

Water solubility(% dry matter)

Stickinessscore

Appearancescore

1 50 50 0 0 9.64 48.24 136 1372 65 35 0 0 8.53 37.72 90 146

3 50 35 15 0 5.38 36.98 29 684 50 40 0 10 10.17 50.85 148 1185 55 35 0 10 9.49 45.18 120 1316 50 35 5 10 9.97 45.34 21 447 55 45 0 0 9.00 43.90 138 1298 60 40 0 0 8.71 42.67 97 1339 50 43.3 0 6.7 10.91 50.77 142 120

10 58.3 35 0 6.7 10.31 42.32 89 12711 50 45 5 0 8.51 43.47 28 8812 50 40 10 0 7.11 41.85 9 7513 60 35 5 0 7.63 37.33 5 10414 55 35 10 0 6.52 37.56 3 7715 50 35 11.7 3.3 8.42 39.56 7 3216 50 35 8.3 6.7 9.72 41.56 16 5017 53.3 38.4 3.3 5 10.46 44.38 12 11818 53.3 38.4 3.3 5 10.51 43.20 16 11119 53.3 38.4 3.3 5 10.02 44.75 24 13020 53.3 38.4 3.3 5 10.35 44.63 28 125

a Experimental runs were performed in random order.

Table 2Analysis of variance and regression coefficients of the first and second order models for four responses

Source Sum of squares

Linear models Quadratic modelsdf WS (% dry matter)

(n= 2)AP (n= 4) df WVP (g mm m2 h1 kPa1)

(n= 1)ST (n= 3)

Model 3 295.50*** 17367*** 9 41.34*** 53947***

Residual 16 14.29 4832 10 0.25 2689Lack of fit 13 12.77 4626 7 0.11 2529Pure error 3 1.52 206 3 0.14 160Corrected total 19 309.79 22199 19 41.59 56636R2 0.95 0.78 0.99 0.95Regression coefficienta

bn0 44.1*** 105.1*** 10.3*** 30.7

bn1 32.1*** 77.2 4.7*** 141.7

bn2 41.5*** 18.3 5.3*** 293.7**

bn3 38.1*** 649.9*** 9.4*** 1533.7**

bn4 50.4***

249.7**

15.9***

281.4*

bn11 7.0 228.0bn22 9.6 287.4bn33 65.4

** 13704.7***

bn44 433.0*** 7177.8*

bn12 20.5 364.9bn13 25.1 64.3bn14 25.2 2108.6bn23 18.8 2417.4bn24 59.5

** 1098.2bn34 210.9

*** 425.1

a These are coefficients of Eq.(2) for WS and AP, and Eq.(3) for WVP and ST, respectively.bn0is the value of the response at the standard referencemixture and the numerals 1, 2, 3 and 4 refer to whey protein isolate, sorbitol, beeswax and potassium sorbate, respectively.* Significant at 10% level.

** Significant at 5% level.*** Significant at 1% level.

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for WVP and ST, on the other hand, were significant(P6 0.01) without any significant lack of fit (P6 0.05).Based on these results, linear models were chosen for WSand AP, while quadratic models were selected for WVPand ST. The analysis of variance (ANOVA) and the regres-sion coefficients (bs) for the models developed for four

responses are shown in Table 2. The analysis of variancefor four response variables showed that all modelsdeveloped were statistically significant (P6 0.01) with nosignificant lack of fit, which suggested that they adequatelydescribed the true functions.

3.2. Water vapor permeability

A trace plot using Coxs direction (Cox, 1971) wasgenerated based on the model chosen for WVP to investi-gate the effect of each mixture component on WVP(Fig. 1). The trace plot shows how the response changeswhen changing the concentration of each mixture compo-nent while keeping all others in a constant ratio. This isnecessary because when the amount of one mixture compo-nent increases, the amounts of all others decrease, but theirratio to one another remains constant. The center of thetrace plot, showing the reference mixture, was the centroidof the design. The composition of the reference mixture interms of actual units was protein = 0.533, sorbitol = 0.384,beeswax = 0.033 and potassium sorbate = 0.050.

The trace plot for WVP (Fig. 1) revealed that WVP ofthe films were influenced by all the mixture components.The addition of protein and beeswax decreased WVP,

while the increase in sorbitol increased WVP. Potassiumsorbate was the most effective factor that adversely affectedWVP. The curvilinear effect of potassium sorbate on WVPimplied that quadratic terms for potassium sorbate and theinteractions between potassium sorbate and some mixturecomponents could be significant. As shown in Table 2,

not only was the second order term for potassium sorbatesignificant, but also the interaction terms between sorbitoland potassium sorbate, and beeswax and potassium sor-bate were significant.

3.3. Water solubility

Resistance of edible-antimicrobial films to water is desir-able if the film is to be used for the preservation of interme-diate or high moisture foods. An antimicrobial film withpoor water resistance will dissolve quickly, causing the filmto lose its antimicrobial agent. This will increase the diffu-sion of the preservative from the surface to the bulk of thefood, resulting in low preservative concentrations at thefood surface.

Whey protein films with potassium sorbate did notdissolve or break apart after they were immersed into waterand dried for 24 h. This was an indicative of highly stableprotein-polymer network. The influence of protein, sorbi-tol, beeswax and potassium sorbate on WS is shown inFig. 2. Trace plots of each component on WS showed thatall mixture components affected WS. Protein and beeswaxhad negative impacts on WS, while sorbitol and potassiumsorbate positively affected WS. This means that the

Fig. 1. Trace plot showing the effects of each mixture component on watervapor permeability (A = protein, B = sorbitol, C = beeswax and D =

potassium sorbate).

Fig. 2. Trace plot showing the effects of each mixture component on watersolubility (A = protein, B = sorbitol, C = beeswax and D = potassium

sorbate).



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addition of more protein and beeswax to the filmformulation produce films with high water resistance. Onthe other hand, increasing the amounts of sorbitol andpotassium sorbate in the films reduces the resistance offilms to water.

3.4. Sensory

Fig. 3showed that ST was strongly influenced by bees-wax. However, potassium sorbate and sorbitol also affectedST, but in a lesser extent than beeswax. The addition ofpotassium sorbate below the reference mixture reducedST, but further addition increased ST beyond the referencemixture. Increasing the amount of sorbitol in the filmsincreased ST. Protein seemed to be not an important factorinfluencing ST. The presence of curvature in beeswax andpotassium sorbate implied that ST could be affected bythe second order terms of these components. This behaviorwas confirmed by the existence of significant interactionsamong quadratic terms for beeswax and potassium sorbatein the model developed for ST as shown inTable 2.

The effect of protein, sorbitol, beeswax and potassiumsorbate on the AP of the films is shown inFig. 4. The slopeof the trace plot for beeswax was steeper than any of thecomponents in the mixture, indicating that beeswax wasthe primary factor influencing AP. Potassium sorbate neg-atively affected AP similar to that of beeswax, but in a les-ser extent. Protein and sorbitol seemed not to have anyeffects on AP.

3.5. Locating the optimum

Predictive models were used to graphically represent thesystem. Contour plots were generated, by plotting each

response to three mixture factors, while the fourth factorwas kept constant. Numerous contour plots were createdfor each response to better understand the responses ofthe system within the experimental region. For eachresponse, a mixture contour plot was obtained at a specificvalue of protein concentration because ST and AP were notaffected by the amount of protein in the films. Subsequentmixture contour plots were generated at other values ofprotein concentrations. The contour plots of fourresponses obtained for each specific value of protein werethen superimposed to find an optimum region with limitingresponse values (constraints). These constraints were asfollows: (a) the stickiness must be minimum based on thesensory scores; (b) the appearance score of at least 80 mustbe achieved as determined by the panelists; (c) the watervapor permeability must be as low as possible, the valueof WVP = 9 g mm m2 h1 kPa1 was chosen as a maxi-mum reference; and (d) the water solubility of at least39% was chosen based on the solubility values reportedby Gontard et al. (1992) and Jangchud and Chinnan(1999) for wheat gluten and peanut protein filmsrespectively.

Fig. 5 shows the computer generated mixture contourplots for the water vapor permeability, water solubilitystickiness and appearance of films when the proportion

of protein was at its reference value (protein = 0.533)

Fig. 3. Trace plot showing the effects of each mixture component onstickiness (A = protein, B = sorbitol, C = beeswax and D = potassium

sorbate).

Fig. 4. Trace plot showing the effects of each mixture component onappearance (A = protein, B = sorbitol, C = beeswax and D = potassiumsorbate).



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The shaded area inFig. 6shows the optimum region for allfour responses based on the constraints given above. Thepredicted optimum mixture proportions of protein = 0.53,sorbitol = 0.38, beeswax = 0.08 and potassium sor-

bate = 0.01 would yield an edible film with minimum stick-

iness, WVP6 9 g mm m2 h1 kPa1, water solubilityP39% and appearance scoreP 80.

The formation of edible films and coatings composed ofwhey is not only important in finding new uses for whey

proteins, but also in improving the microbial stability of

Fig. 5. Computer generated mixture contour plots for (a) water vapor permeability (g mm m 2 h1 kPa1); (b) water solubility (% dry matter); (c)stickiness and (d) appearance at 53.3% protein concentration.



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foods particularly in presence of preservatives in filmformulations. Ozdemir (1999) showed that whey proteinfilms containing potassium sorbate effectively suppressedthe growth of yeasts and molds by extending the lag periodbefore the growth became apparent. Potassium sorbate

incorporated whey protein films help provide improvedfood safety and stability, thereby increasing shelf life.These films are required to have preservative diffusion coef-ficients smaller than those in food products to slow downthe diffusion of preservative from the food surface to thebulk of the food. Film composition is of primary impor-tance affecting the diffusion of preservatives in edible filmformulations (Ozdemir & Floros, 2003). Ozdemir andFloros (2001)determined potassium sorbate diffusion coef-ficients in whey protein films when the films are in contactwith an intermediate moisture model food system with awater activity of 0.80. Potassium sorbate diffusion coeffi-

cients in the films ranged from 5.38 to 9.76 10

11

m

2

s

1

.The change in the diffusivity of potassium sorbate in theoptimum region is shown by the dashed lines (Fig. 6).

4. Conclusions

Mixture response surface methodology and graphicaloptimization methods were effective in better understand-ing the effect of film formulation on water vapor permeabil-ity, water solubility and organoleptic quality of wheyprotein films containing potassium sorbate. The predictedoptimum mixture proportions of protein = 0.53, sorbi-tol = 0.38, beeswax = 0.08 and potassium sorbate = 0.01

would yield an edible film with minimum stickiness,

WVP 6 9 g mm m2 h1 kPa1, water solubilityP 39%and appearance scoreP 80. The addition of proteinreduced WVP and WS, but it had no effect on ST andAP. Sorbitol had a positive impact on WVP, WS and STand it did not affect AP. All four responses were negativelyinfluenced by beeswax. Potassium sorbate significantly

increased WVP, WS and ST, but it had a negative impacton AP. The films could be used particularly for bakeryproducts, cookies, individually wrapped cheeses, nutsbiscuits, chocolate surfaces and as casing for sausagesand salamis. Edible films and coatings carrying antimicro-bial agents are of particular interest to both food proces-sors and food scientists because they are formed fromnatural materials. Edible films with preservatives not onlyhelp provide improved food safety and stability like antimi-crobial plastic films, but also overcome the migration ofpackage components from plastic packaging materials.

References

ASTM (1997). Designation E 96-95: Standard test method for water vaportransmission of materials. In Annual book of ASTM standards(pp. 752759). Philadelphia, Pennsylvania: American Society foTesting and Materials.

Baldwin, E. A., Nisperos-Carriedo, M. O., & Baker, R. A. (1995). Use ofedible coatings to preserve quality of lightly (and slightly) processedproducts. Critical Reviews in Food Science and Nutrition, 35 , 509524

Banerjee, R., & Chen, H. (1995). Functional properties of edible filmsusing whey protein concentrate. Journal of Dairy Science, 7816731683.

Chen, H. (1995). Functional properties and applications of edible filmsmade of milk proteins. Journal of Dairy Science, 78, 25632583.

Cornell, J. A. (1990). Experiments with mixtures: designs, models, and

analysis of mixture data (2nd ed.). New York: Wiley.Cox, D. R. (1971). A note on polynomial response functions for mixtures

Biometrika, 58, 155159.Debeaufort, F., Quezada-Gallo, J.-A., & Voilley, A. (1998). Edible film

and coatings: tomorrows packagings: a review. Critical Reviews inFood Science and Nutrition, 38, 299313.

Gontard, N., Guilbert, S., & Cuq, J.-L. (1992). Edible wheat gluten filmsInfluence of the main process variables on film properties usingresponse surface methodology. Journal of Food Science, 57, 190195199.

Huffman, L. M. (1996). Processing whey protein for use as a foodingredient. Food Technology, 50(2), 4952.

Jangchud, A., & Chinnan, M. S. (1999). Peanut protein film as affected bydrying temperature and pH of film forming solution. Journal of FoodScience, 64, 153157.

Kester, J. J., & Fennema, O. R. (1986). Edible films and coatings: a reviewFood Technology, 40(12), 4759.

Kinsella, J. E. (1984). Milk proteins: physicochemical and functionaproperties.Critical Reviews in Food Science and Nutrition, 21, 197262

Krochta, J. M., & De Mulder-Johnston, C. (1997). Edible and biode-gradable films: Challenges and opportunities. Food Technology, 51(2)6174.

McHugh, T. H., Avena-Bustillos, R., & Krochta, J. M. (1993). Hydrophilic edible films: Modified procedure for water vapor permeabilityand explanation of thickness effects. Journal of Food Science, 58899903.

McHugh, T. H., Aujard, J.-F., & Krochta, J. M. (1994). Plasticized wheyprotein edible films: water vapor permeability properties. Journal ofFood Science, 59, 416419, 423.

McHugh, T. H., & Krochta, J. M. (1994a). Milk-protein-based edible

films and coatings. Food Technology, 48(1), 97103.

Fig. 6. Optimum region obtained by superimposing contour plots of allfour responses generated at 53.3% protein concentration. Shaded arearepresents optimum region with minimum stickiness, WVP 69 g mm m2 h1 kPa1, WSP 39% and APP 80. Dashed lines showthe change in potassium sorbate diffusivity (1011 m2 s1).



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McHugh, T. H., & Krochta, J. M. (1994b). Sorbitol- vs glycerol-plasticized whey protein edible films: integrated oxygen permeabilityand tensile property evaluation. Journal of Agricultural and FoodChemistry, 42, 841845.

McHugh, T. H., & Krochta, J. M. (1994c). Water vapor permeabilityproperties of edible whey proteinlipid emulsion films. Journal of theAmerican Oil Chemists Society, 71, 307312.

Miller, K. S., & Krochta, J. M. (1997). Oxygen and aroma barrierproperties of edible films: a review. Trends in Food Science andTechnology, 8, 228237.

Myers, R. H., & Montgomery, D. C. (1995). Response surface method-ology: process and product optimization using designed experiments.New York: Wiley.

Ozdemir, M. (1999).Antimicrobial releasing edible whey protein films andcoatings. Ph.D. dissertation, Purdue University, West Lafayette,Indiana, USA.

Ozdemir, M., & Floros, J. D. (2001). Analysis and modeling of potassiumsorbate diffusion through edible whey protein films. Journal of FoodEngineering, 47, 149155.

Ozdemir, M., & Floros, J. D. (2003). Film composition effects on diffusionof potassium sorbate through whey protein films. Journal of FoodScience, 68, 511516.

Ozdemir, M., & Floros, J. D. (2008). Optimization of edible whey proteinfilms containing preservatives for mechanical and optical properties.Journal of Food Engineering, 84, 116123.

Rhim, J.-W., & Ng, P. K. W. (2007). Natural biopolymer-basednanocomposite films for packaging applications. Critical Reviews inFood Science and Nutrition, 47, 411433.

Robach, M. C. (1979a). Influence of potassium sorbate on growth ofPseudomonas putrefaciens. Journal of Food Protection, 42, 312313.

Robach, M. C. (1979b). Extension of shelf-life of fresh, whole broilers,using a potassium sorbate dip.Journal of Food Protection, 42, 855857.

Robach, M. C., & Sofos, J. N. (1982). Use of sorbates in meat products,fresh poultry and poultry products. A review. Journal of FoodProtection, 45, 374383.

Shellhammer, T. H., & Krochta, J. M. (1997). Whey protein emulsion filmperformance as affected by lipid type and amount. Journal of FoodScience, 62, 390394.

Sofos, J. N., Busta, F. F., & Allen, C. E. (1980). Influence of pH onClostridium botulinum control by sodium nitrite and sorbic acid inchicken emulsions. Journal of Food Science, 45, 712.

Stat-Ease, Inc. (1996). Design-Expert software, version 5.0. Minneapolis,MN: Stat-Ease, Inc..

Stone, H., & Sidel, J. L. (1993).Sensory evaluation practices(2nd ed.). SanDiego, California: Academic.

Stuchell, Y. M., & Krochta, J. M. (1994). Enzymatic treatments andthermal effects on edible soy protein films. Journal of Food Science, 59,

13321337.Umetri AB (1997). Modde software, version 4.0. Umea, Sweden: Umetri,AB.


Documents

Ozdemir e Floros, 2008