Whey Protein Isolate Coatings Research Articles

Sheep's Second Cheese Whey Edible Coatings with Oregano and Clary Sage Essential Oils Used as Sustainable Packaging Material in Cheese.

Sheep's second cheese whey (SCW), the by-product resulting from whey cheese production, was used as a component of cheese coatings containing oregano (Origanum compactum) and clary sage (Salvia sclarea) essential oils (EOs). SCW powder was obtained by the ultrafiltration/diafiltration of SCW followed by reverse osmosis and freeze drying. The coatings were produced with a mixture of SCW and whey protein isolate (WPI) using glycerol as plasticizer. Model cheeses were produced with cow´s milk and those containing SCW:WPI coatings; those with and without EOs were compared to controls without coating and with a commercial coating containing natamycin. At the end of ripening (28 days), the cheeses containing EOs presented higher water activity (ca. 0.930) and moisture content, as well as lower titratable acidity. Concerning color parameters, significant differences were also observed between products and as a result of ripening time. However, the use of SCW:WPI coatings did not significantly influence the color parameters at the end of ripening. Regarding texture parameters, the cheeses containing SCW:WPI coatings presented significantly lower values for hardness, chewiness, and gumminess. Significant differences were also observed for all microbial groups evaluated either between products and as a result of ripening time. In all cases, lactobacilli and lactococci counts surpassed log 7-8 CFU/g, while the counts of yeasts and molds increased steadily from ca. log 3 to log 6 CFU/g. The lowest counts of yeasts and molds were observed in the samples containing natamycin, but nonsignificant differences between products were observed. In conclusion, SCW:WPI cheese coatings can successfully substitute commercial coatings with the advantage of being edible packaging materials manufactured with by-products.

The Effect of Whey Protein-Based Edible Coatings Incorporated with Lemon and Lemongrass Essential Oils on the Quality Attributes of Fresh-Cut Pears during Storage

This study aimed to determine the effect of edible coatings based on whey protein isolate and essential oils (lemon and lemongrass) on the colour, hardness, polyphenols and flavonoids content, structure, and sensory attributes of fresh-cut pears during storage at 4 °C. The optical and barrier properties of the edible films were also determined. Analysed films showed good transparency (Lightness 86.6–95.0) and excellent oxygen and carbon dioxide permeability, which were reduced due to the presence of lemon and lemongrass essential oils. Pears were coated by immersion in a solution containing 8% of whey protein isolate and the addition of lemon oil at 1.0% or lemongrass essential oil at 0.5%. Coating caused a reduction in colour changes, loss in hardness, polyphenols and flavonoids. The study showed that the highest efficiency was demonstrated by the whey protein isolate coatings without the addition of essential oils by preserving the colour and firmness of fresh-cut pears. For these samples, the highest sensory acceptability was also achieved.

Effect of the processing and storage conditions on lipid deterioration and organoleptic properties of baklava

Effect of antioxidant (BHA) and a whey protein isolate coating (WPIc) on lipid deterioration and organoleptic properties of baklava (BK) were investigated. Four batches of BK were prepared; the first and second batches were control and BK with WPIc, while the third and fourth were BK with BHA and BK with BHA and WPIc (BHA + WPIc). The samples were stratified in cardboard boxes, shrink-wrapped, divided into three subsamples and stored at 30, 23 and 8°C for 4 months. The extent of lipid deterioration was monitored by hydrolytic rancidity (FFA%), peroxide value (PV), (7-ketocholesterol), and organoleptic properties. The BHA + WPIc treatment significantly retarded the development of FFA%, PV and 7-ketocholesterol and extended the shelf-life to 2 months at 23°C and >4 months at 8°C. Storage time and temperature affected FFA%, whereas storage time affected PV. Strong off-flavor was detected at 2 months and >4 months in the control and treated samples. Practical applications Baklava is a traditional, sweet bakery product, that is, very popular in the Mediterranean region. This product is rich in fat and nuts and is usually packaged in airtight shrink-wrapped boxes. These boxes are normally kept loosely closed after each consumption session. Therefore, the product can suffer from early loss of package integrity and changes in quality from exposure to atmospheric oxygen. Work was undertaken to evaluate the addition of BHA to BK and application of WPI edible coatings for their effectiveness in retarding development of undesirable reactions in baklava during normal storage and consumer use.

Impact of whey protein isolate coatings containing different antimicrobial agents on sliced bologna-type sausage during refrigerated storage

Abstract In this study, we aimed to determine the possibility of using the edible whey protein isolates coatings containing different antimicrobial agents on the bologna-type sausage slices and the inactivation effects of these coatings against Listeria innocua. For this purpose, edible whey protein isolates (WPI) coatings were prepared to contain essential oils (thyme, coriander, pimento, rosemary, basil), potassium sorbate (PS), sodium benzoate (SB)(4% w/v) and Nisin(10.000 IU). The antimicrobial effect against L. innocua, sensory characteristics (appearance, color, odor, texture, flavor and overall acceptability) and physical (color) and chemical (pH and water activity) properties of bologna slices coated WPI coatings were determined for during the 35-day period in refrigerated conditions (4±1°C). In conclusion, it was determined that the most effective coatings for L. innocua inactivation were PS, SB, and pimento essential oil, approximately 4.69, 4.45 and 4.16 log CFU/g, respectively. The most effective coating on the pH values (5.90-6.04) was established to be WPI coatings containing Nisin. It has been found that WPI coatings containing thyme essential oil provided the lowest water activity values with 0.945. In addition, it was possible to say that the most favored type of coating for sausage samples was Nisin-WPI coatings with 7.63- 8.33 sensory scores.

Influences of Different Coating Materials on the Quality Changes of Hardboiled Salted Duck Eggs under Ambient Storage

Abstract The present study investigated the influences of selected coatings (paraffin wax (PW), chitosan (CH), whey protein isolate (WPI), and soy protein isolate (SPI)) on the quality changes of hardboiled salted duck eggs when kept under ambient temperature (30±2 oC). At 5-day intervals for 15 days, samples were tested for color (L*, C*, and h˚), shell strength, weight loss, microbial analysis, water activity, moisture, pH, salt content, TBARS, and sensory analysis. L*, C* and h˚ gradually decreased in egg white, whereas C* and h˚ gradually increased in egg yolk. Shell strength gradually decreased in all cases, and weight loss similarly increased throughout the storage. PW and WPI coatings gave the best shell strengths and the least weight loss. The aw was not significantly different between the treatments. WPI and PW retained the most moisture. A slight decrease in pH was observed in all the samples (P ≥ 0.05). On the other hand, salt content gradually increased with storage time, and the WPI and SPI treatments gave < 2% salt accumulation. TBARS steadily increased throughout storage, and the WPI samples had the least lipid oxidation. TPC, mold, and yeast at the end of storage were the least with the WPI treatment. Both the storage period and coating material choice significantly influenced the sensory scores that declined throughout the storage. Overall, the WPI coating treatment gave the best results.

Edible bacteriophage based antimicrobial coating on fish feed for enhanced treatment of bacterial infections in aquaculture industry

As the fastest growing food-producing industry in the world, aquaculture industries frequently suffer from the outbreaks of various bacterial diseases. There is a need to develop alternatives to antibiotics to address the challenge of bacterial infections without using conventional antibiotics. This study developed a bacteriophage based edible antimicrobial coatings on fish feed, providing an effective biological control strategy for treating fish and human pathogens in an aquaculture system. The edible whey protein isolate (WPI) coatings were effective in enhancing loading of phages on fish feed pellets and reducing the loss of phage activity during storage of feed. The feasibility of both dip coating and air-brush spray coating methods were demonstrated in this study. The edible coatings decreased the release of phages in salt water by >1 log PFU/pellet after 2-h exposure as compared to control coatings on feed without the biopolymer coatings. The simulated gastric-intestinal digestion assay demonstrates that this coating provides enhanced stability of phages in a simulated gastric environment and a significant bacterial reduction (3–5 logs of target bacteria) in a simulated intestinal digestion. These antimicrobial activity results were demonstrated using a model bacterium (E. coli) and a fish pathogen (Vibrio spp.). Overall, the results show that phage incorporated WPI coatings on fish feed can be an effective approach for enhancing the treatment fish infections, reducing the risk of antibiotic resistance in aquaculture environment, and improving the safety and sustainability of aquaculture industry.

Effects of whey protein isolate based coating enriched with Zingiber officinale and Matricaria recutita essential oils on the quality of refrigerated rainbow trout

AbstractThe present study aimed to investigate the effect of whey protein isolate (WPI) coating enriched with essential oils (ginger and chamomile) on rainbow trout fillets during storage at 4°C. Samples were analyzed at 0, 3, 6, 9, 12, and 15 days for microbiological (total aerobic mesophilic bacteria, psychrotrophic bacteria, lactic acid bacteria, Pseudomonas), chemical analyses (pH, thiobarbituric acid reactive substances‐TBARS, total volatile base nitrogen‐TVB‐N, peroxide value [PV]) and sensory quality (odor, taste, tissue, appearance). Bacterial growth was inhibited in samples with high concentrations of essential oils due to its antimicrobial activity. During the storage period, TVB‐N, TBARS, and PVs content gradually increased in all groups, and significant differences were found between the groups (p &lt; .05). In conclusion, the addition of of ginger and chamomile essential oils to WPI coatings showed a positive effect on the rainbow trout shelf‐life.Practical applicationsWhey protein is a by‐product of the cheese‐making industry and is already known as an excellent barrier to oxygen, aroma, and oil and can be used as a coating material for improving the oxygen barrier property of food packaging. The use of an essential oil in fresh fish preservation may be considered an alternative “natural” additive, extending the shelf life of the product. Our study has clearly shown that addition of ginger and camolime essential oil and whey protein isolate coating in fish resulted in longer shelf life, and this method could be commercially used.

Quality improvement of rainbow trout fillets by whey protein isolate coatings containing electrospun poly(ε-caprolactone) nanofibers with Urtica dioica L. extract during storage

Novel bioactive coatings were prepared to extend the quality and shelf life of fresh fish fillets of rainbow trout (Oncorhynchus mykiss). For this, whey protein isolate (WPI) with 96 g/100 g protein content was used as the coating-forming agent with glycerol in a ratio of 3.3 g/100 mL as plasticizer. Poly(ε-caprolactone) (PCL) nanofibers containing extract of Urtica dioica L., often called stinging nettle, at 60:40 (g:g) were produced by electrospinning. These were then incorporated into WPI at different concentrations, i.e., 50 and 70 g/100 g. Fish fillets protected by means of the functionalized coatings were stored for 15 days at 4 °C. Protected fish fillets exhibited higher antimicrobial efficiency against mesophilic, psychrophilic, and lactic acid bacteria as well as Enterobacteriaceae than equivalent coatings containing Urtica dioica L. water extract. In particular, incorporation of 70 g/100 g PCL nanofibers exhibited the lowest counts in both bacterial growth and values in total volatile basic nitrogen (TVB-N) and thiobarbituric acid (TBA) during storage. Additionally, the coatings successfully provided antioxidant activity that could help to increase fish fillets' quality and favor their preservation.

Modified whey protein coatings for improved gas barrier properties of biodegradable films

As a result of environmental concern, there is an increasing interest in the development of biodegradable polymers for packaging with suitable properties, as an alternative to the synthetic petroleum-based polymers. However, such biodegradable polymers are prevented for use in wide industrial and commercial packaging because of their limited gas and vapor barrier properties. This obstacle urges innovative strategies to achieve enhanced gas barrier properties using “bio-layering” technologies. Whey protein isolate (WPI), a by-product of the cheese industry, has quite promising properties for packaging purposes. It possesses good oxygen, aroma, and oil barrier properties; however, its permeability to water vapor is high. In this study, several WPI coatings were obtained, adding polyvinyl alcohol and pectin to improve the coated film properties; in addition, nanoclays were used to improve water vapor barrier properties. Comparison of neat poly (lactic acid) film versus poly (lactic acid) coated with WPI presented advantage of the later: improvement of about 90% in the oxygen barrier properties and about 27% in the water vapor barrier properties. Copyright © 2016 John Wiley & Sons, Ltd.

The Effect of Whey Protein Isolate Coating Enriched with Thyme Essential Oils on Trout Quality at Refrigerated Storage (4 ± 2°C)

ABSTRACTThe present study evaluated the effect of whey protein isolate (WPI) coating enriched with thyme essential oil (EO; 3, 5, and 7%, v/v) on whole trout chemical and microbial quality during refrigerated storage at 4 ± 2°C. As a result of this study, the addition of thyme essential oil to WPI coatings enhanced quality significantly better than that of the control and WPI coating without thyme essential oil during refrigerated storage, and this effect increased with an increase in the thyme EO concentration in WPI coating.

Antimicrobial efficiency of edible coatings on the preservation of chicken breast fillets

To improve the quality and extend the shelf-life of chicken breast, Whey Protein Isolate (WPI) edible coatings with oregano or clove essential oils (EOs) incorporated as natural antimicrobials have been developed. These insoluble, homogeneous and continuous WPI coatings formed an imperceptible second skin covering the chicken breast. The antimicrobial effect of the coatings depended on their EO concentration (the higher the better), EO type (oregano EO the most active) and on the microbiological group analysed (Pseudomonas spp. the most resistant). Films with 20 g kg−1 of oregano EO showed their efficacy by doubling the storage time of chicken breast (from 6 to 13 days), keeping most of the microbiological groups below the recommended limits for distribution and consumption of chicken breast. By comparing the effects of the direct addition of the EOs onto the chicken breast surfaces and the results brought about by the development of edible coatings the usefulness and functionality of the latter as carriers of antimicrobials has been confirmed.

Understanding the effects of various edible coatings on the storability of fresh cherry

Abstractn this work, cherries, which have a very short shelf life, were packaged after being coated with various edible coatings [whey protein isolate (WPI), chitosan and shellac]. The changes in gas composition, weight loss, Brix, pH, electrical conductivity and firmness were measured periodically up to 11 days after harvest to compare the effects of the applied coatings. Fourier transform near‐infrared (FT‐NIR) spectroscopymeasurements were also taken individually. After storage, the gas composition within trays was about 1–10% O2 and 14–47% CO2. The lowest weight loss (25.56%) was observed in the shellac‐coated cherries, while the highest loss (48.58%) occurred in the control group. Coated cherries exhibited a significantly lower pH and electrical conductivity than the uncoated ones. The control group presented the highest total soluble solid (TSS) values (21.29) and shellac coating had (17.25) the lowest. At the end of storage, the highest ascorbic acid (AA) content was 0.64 mg/100 ml in the shellac‐coated cherries, and the lowest AA content of 0.40 mg/100 ml was measured in the control group. Firmness was maintained by coating, especially with shellac (3.734 N), whereas the control had the lowest firmness measured (2.138 N) at the end of storage. There were differences between the absorbance spectra for the coated and control cherries at the end of storage. This research concludes that shellac coating is more effective in reducing the respiration rate and maintaining the quality parameters of cherries than chitosan and WPI coatings. Major benefits of coatings were observed in lessening the weight‐loss process and in maintaining firmness, which were also supported by the FT‐NIR measurements. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Coating of Peanuts with Edible Whey Protein Film Containing α‐Tocopherol and Ascorbyl Palmitate

Physical properties of whey protein isolate (WPI) coating solution incorporating ascorbic palmitate (AP) and alpha-tocopherol (tocopherol) were characterized, and the antioxidant activity of dried WPI coatings against lipid oxidation in roasted peanuts were investigated. The AP and tocopherol were mixed into a 10% (w/w) WPI solution containing 6.7% glycerol. Process 1 (P1) blended an AP and tocopherol mixture directly into the WPI solution using a high-speed homogenizer. Process 2 (P2) used ethanol as a solvent for dissolving AP and tocopherol into the WPI solution. The viscosity and turbidity of the WPI coating solution showed the Newtonian fluid behavior, and 0.25% of critical concentration of AP in WPI solution rheology. After peanuts were coated with WPI solutions, color changes of peanuts were measured during 16 wk of storage at 25 degrees C, and the oxidation of peanuts was determined by hexanal analysis using solid-phase micro-extraction samplers and GC-MS. Regardless of the presence of antioxidants in the coating layer, the formation of hexanal from the oxidation of peanut lipids was reduced by WPI coatings, which indicates WPI coatings protected the peanuts from oxygen permeation and oxidation. However, the incorporation of antioxidants in the WPI coating layer did not show a significant difference in hexanal production from that of WPI coating treatment without incorporation of antioxidants.

Evaluation of Antibacterial Activity of Whey Protein Isolate Coating Incorporated with Nisin, Grape Seed Extract, Malic Acid, and EDTA on a Turkey Frankfurter System

The effectiveness of whey protein isolate (WPI) coatings incorporated with grape seed extract (GSE), nisin (N), malic acid (MA), and ethylenediamine tetraacetic acid (EDTA) and their combinations to inhibit the growth of Listeria monocytogenes, E. coli O157:H7, and Salmonella typhimurium were evaluated in a turkey frankfurter system through surface inoculation (approximately 10(6) CFU/g) of pathogens. The inoculated frankfurters were dipped into WPI film forming solutions both with and without the addition of antimicrobial agents (GSE, MA, or N and EDTA, or combinations). Samples were stored at 4 degrees C for 28 d. The L. monocytogenes population (5.5 log/g) decreased to 2.3 log/g after 28 d at 4 degrees C in the samples containing nisin (6000 IU/g) combined with GSE (0.5%) and MA (1.0%). The S. typhimurium population (6.0 log/g) was decreased to approximately 1 log cycles after 28 d at 4 degrees C in the samples coated with WPI containing a combination of N, MA, GSE, and EDTA. The E. coli O157:H7 population (6.15 log/g) was decreased by 4.6 log cycles after 28 d in samples containing WPI coating incorporated with N, MA, and EDTA. These findings demonstrated that the use of an edible film coating containing nisin, organic acids, and natural extracts is a promising means of controlling the growth and recontamination of L. monocytogenes, S. typhimurium, and E. coli O157:H7 in ready-to-eat poultry products.

IMPROVEMENT OF OXIDATIVE STABILITY OF ROASTED PEANUTS BY EDIBLE COATINGS AND ULTRASONICATION

In this study, an innovative method was developed to improve the shelf life of roasted peanuts. Sonication was combined with edible coating for enhancing the oxidative stability of roasted peanuts. Georgia green runner peanuts were roasted, subjected to sonication and then coated with whey protein isolate (WPI), ZEIN and carboxymethyl cellulose (CMC). Relative to the control, the oxidative stability of roasted-coated samples was improved by 80, 38 and 5% for CMC, WPI and ZEIN coating, respectively, while roasted-sonicated-coated samples were improved by 91, 52 and 27% for CMC, WPI and ZEIN coating, respectively. Sonication prior to coating resulted in 11, 14 and 22% improvement beyond the CMC, WPI and ZEIN coatings, respectively. Texture analysis showed there were no significant differences (P < 0.05) in peanut texture between the treated and the control. Color results showed the HunterLab color parameters L, a, and b for most of the treatments did not have significant differences (P < 0.05) compared with the control. PRACTICAL APPLICATIONS Edible coatings used in this study (carboxymethyl cellulose, whey protein isolate and ZEIN) were capable of acting as oxygen barriers to reduce peanut lipid rancidity. This research demonstrated the potential of power ultrasound to remove lipids from the peanut surfaces and improve coating adhesion. The texture and the color of coated peanuts did not change over the storage period. This study indicated that edible coatings in combination with sonication provided an alternative way for improving the oxidative stability and eventually the shelf life and quality of roasted peanuts.

Whey Protein-Sucrose Coating Gloss and Integrity Stabilization by Crystallization Inhibitors

Whey protein coatings protect foods from change and deterioration and can extend product shelf life. However, because they are also made from food materials, whey protein coatings may also change over time if not properly formulated. Whey protein isolate (WPI)-sucrose high-gloss coatings, with and without crystallization inhibitors, were formed on chocolate-covered peanuts. The objective was to determine the effectiveness of crystallization inhibitors on preventing cracking of coatings and loss of coating gloss caused by sucrose crystallization during product storage. The 4 inhibitors tested were lactose, modified starch, polyvinylpyrrolidone, and raffinose. The WPI-coated chocolate-covered peanuts were stored for 119 d in 23%, 33%, and 44% relative humidity (RH) at 25°C. Gloss of the WPI coatings was measured periodically with a gloss-analysis system. It was found that raffinose is the most effective inhibitor of sucrose crystallization in whey protein-sucrose coatings. WPI coatings containing raffinose had significantly higher gloss values than all other coatings. For raffinose-containing samples stored in 23% and 33% RH environments, less than 3% of gloss was lost during storage. In 44% RH, the raffinose coating system had significantly less gloss fade than other WPI-sucrose coatings. This information can be used to improve the effectiveness of water-based high-gloss edible coatings.

Inhibition of Salmonella enterica and Escherichia coli O157:H7 on Roasted Turkey by Edible Whey Protein Coatings Incorporating the Lactoperoxidase System

The effects of whey protein isolate (WPI) coatings incorporating a lactoperoxidase system (LPOS) on the inhibition of Salmonella enterica and Escherichia coli O157:H7 on roasted turkey were studied by testing the initial inhibition as well as the inhibition during storage. The initial antimicrobial effects of WPI coatings incorporating LPOS (LPOS-WPI coatings) were examined with various inoculation levels and LPOS concentrations. LPOS-WPI coatings with 7 and 4% of LPOS demonstrated initial 3- and 2-log CFU/g reductions of S. enterica and E. coli O157:H7, respectively. The antimicrobial effect was observed regardless of whether the turkey was inoculated before or after coating. Storage studies were conducted for 42 days at 4 and 10°C with S. enterica (6.0 log CFU/g)– or E. coli O157:H7 (5.6 log CFU/g)–inoculated sliced turkey. LPOS concentrations for the storage studies of S. enterica and E. coli O157:H7 were 5 and 3% (wt/wt), respectively, in the coating solution and in an LPOS solution for spreading. LPOS-WPI coatings inhibited the growth of both S. enterica and E. coli O157:H7 in turkey at both 4 and 10°C for 42 days. The inhibition was more pronounced when the coating was formed on the surface of the turkey prior to inoculation than when the coating was formed on the inoculated surface. More effective inhibition of S. enterica and E. coli O157:H7 was observed with the LPOS-WPI coatings than with the LPOS solution-spreading treatment. LPOSWPI coatings also retarded the growth of total aerobes during storage.

Listeria monocytogenes Inhibition by Whey Protein Films and Coatings Incorporating Lysozyme

The effects of whey protein isolate (WPI) films and coatings incorporating lysozyme (LZ) on the inhibition of Listeria monocytogenes both in and on microbial media, as well as on cold-smoked salmon, were studied. The antimicrobial effects of LZ were examined using various growth media by turbidity and plate counting tests. Disc-covering and disc-surface–spreading tests were also used to evaluate the effects of WPI films incorporating LZ. Smoked salmon was used as a model food to test the antimicrobial effects of WPI coatings incorporating LZ, both initially and during storage at 4 and 10°C for 35 days. Tensile properties (elastic modulus, tensile strength, and percentage of elongation), oxygen permeability, and color (Hunter L, a, and b) of WPI films with and without LZ were also compared. LZ inhibited L. monocytogenes in broth and on agar media. The number of cells surviving after LZ treatments depended on the type of media. WPI films incorporating 204 mg of LZ per g of film (dry basis) inhibited the growth of a preparation of 4.4 log CFU/cm2L. monocytogenes. WPI coatings prepared with 25 mg of LZ per g of coating solution initially inactivated more than 2.4, 4.5, and 3.0 log CFU/g of L. monocytogenes, total aerobes, and yeasts and molds in smoked salmon samples, respectively. The WPI coatings incorporating LZ efficiently retarded the growth of L. monocytogenes at both 4 and 10°C. The anti–L. monocytogenes effect of LZ-WPI coating was more noticeable when the coating was applied before inoculation than when the coating was applied after inoculation. Significantly higher elastic modulus values and lower percentage of elongation and oxygen permeability values were measured with the WPI films incorporating LZ than with the plain WPI films.

Whey protein isolate coating and concentration effects on egg shelf life

AbstractThe influences of three different concentrations (6, 12 and 18%) of whey protein isolate (WPI) coatings on shelf‐life enhancements of the fresh egg quality (weight loss, pH, Haugh unit, yolk index and colors) and the shelf life were evaluated at room temperature. All coated eggs showed lower weight loss than uncoated eggs. Less weight loss (2.46 for 12% WPI and 2.38 for 18% WPI) was observed in WPI‐coated eggs. Haugh units (HU) indicated that coated eggs remained in grade ‘A’ during 3 weeks storage period, whereas uncoated (UC) changed from grade ‘A’ to ‘B’ after 1 week of storage. The HU and yolk‐index (YI) values of all WPI‐coated eggs were significantly higher than those of UC. Among the coated eggs, there were no significant differences in HU, but 12 and 18% WPI coated had higher YI than WPI 6% coated and UC. The albumen pH of the UC eggs was significantly higher than that of coated eggs. Yolk lightness (L*) and (b*); shell (a*) and (b*) of coated eggs were not different from UC after 4 weeks. Performance of WPI coatings depended on the concentration up to 12% but not between 12 and 18%. Results also indicated that WPI coatings served as protective barrier for shelf life of the eggs. Copyright © 2005 Society of Chemical Industry

Optical and surface properties of whey protein isolate coatings on plastic films as influenced by substrate, protein concentration, and plasticizer type

AbstractComposite film structures of common plastic polymers including polypropylene (PP) or poly(vinyl chloride) (PVC) with whey protein isolate (WPI) coatings may be obtained by a casting method. Optical and surface properties of the resulting WPI‐coated plastic films, as affected by protein concentration and plasticizer type, were investigated to examine the biopolymer coating effects on surface modification with polymeric substrates of opposite polarity. The measured properties involved specular gloss, color, contact angle, and critical surface energy. Regardless of the substrates, WPI‐coated films possessed excellent gloss and no color, as well as good adhesion between the coating and the substrate when an appropriate plasticizer was added to the coating formulations. The protein concentration did not significantly affect gloss of WPI‐coated plastic films. Among five plasticizers applied, sucrose conferred the most highly reflective and homogeneous surfaces to the coated films. The WPI coatings were very transparent and the coated films with various protein concentrations and plasticizers showed no noticeable changes in color. Experimental results suggest that WPI coatings formulated with a proper plasticizer can improve the visual characteristics of the polymeric substrate and enhance water wettability of the coated plastic films. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 335–343, 2004