Whey Protein Isolate Films Research Articles

Diffusion of the antimicrobial lysozyme from a whey protein coating on smoked salmon

Diffusions of lysozyme (LZ) in whey protein isolate (WPI) films and in smoked salmon coated with LZ-incorporated WPI films (LZ-WPI films) were investigated. Diffusion and partition coefficients for the diffusion for LZ at 4 °C in smoked salmon coated with a LZ-WPI film (WPI:glycerol = 1:1) were determined by fitting mathematical models to the experimental data. Diffusion coefficients for LZ in films were further determined with LZ-WPI films, prepared with different WPI–glycerol ratios (1:1, 2:1, and 3:1) and stored at 4, 10 and 22 °C. The diffusion coefficients for the LZ diffusion in the film (WPI:glycerol = 1:1) and in the salmon at 4 °C and the partition coefficient ( K 12) were 9.8 ± 0.8 × 10 −14 m 2/s, 4.8 ± 3.9 × 10 −11 m 2/s, and 0.4 ± 0.2, respectively. The diffusion coefficients for the LZ diffusion in the films ( D 1) with the different WPI–glycerol ratios and storage temperatures were in the range of 2.5 × 10 −16–3.4 × 10 −13 m 2/s. The D 1 decreased as the WPI–glycerol ratio increased or storage temperature decreased. The E a values for diffusion in 1:1, 2:1, and 3:1 WPI:glycerol films were 16.3, 27.4, and 63.9 kJ/mol, respectively.

Solubility and mechanical properties of heat‐cured whey protein‐based edible films compared with that of collagen and natural casings

Water solubility, tensile strength (TS), wet strength (WS) and elongation at break (%E) of whey protein isolate (WPI) films were compared to that of collagen films and natural casings. Increase in heat‐curing temperature and time caused decreased (P < 0.001) water solubility and increased TS and WS of the films. Heat‐cured WPI films with similar properties (solubility, TS, WS and %E) to collagen films were obtained by optimizing heat‐curing conditions. Overall, natural casings had lower solubility, TS and %E but higher WS than collagen and heat‐cured WPI films. Heat‐cured WPI films have the potential as an alternative to collagen films and casings.

Ascorbic Acid-Containing Whey Protein Film Coatings for Control of Oxidation

A formulation for the whey protein isolate film or coating incorporating ascorbic acid (AA-WPI film or coating) was developed. Tensile and oxygen-barrier properties of the AA-WPI film were measured. Antioxidant effects of the AA-WPI coating on roasted peanuts were studied by comparing the values of peroxide (PO), thiobarbituric acid reactive substance (TBARS), and free-radical-scavenging activity, determined with noncoated peanuts and peanuts coated with WPI with and without ascorbic acid during storage at 21% relative humidity (RH) and 23, 35, and 50 degrees C. The incorporation of AA reduced elongation of WPI films. The oxygen-barrier property of the WPI film was significantly improved by incorporation of AA. The AA-WPI coating retarded lipid oxidation in peanuts significantly at 23, 35, and 50 degrees C. The AA-WPI coated peanuts were more red than noncoated peanuts at all storage temperatures.

Structural effects on the permeability of whey protein films in an aqueous environment

Permeability of whey protein isolate films for salts in an aqueous environment is clearly dependent on the concentration of plasticizer. With increase in glycerol concentration from 20% to 40% the diffusion of salt (CaCl 2) through the film increases from 2.5×10 −10 to 3.6×10 −10 m 2/s. To describe diffusion experiments with a dye (fluorescein free acid (FFA)), an effective diffusion coefficient which increases in time has to be used: for a whey protein film with 30% glycerol an effective diffusion coefficient, which increases from 8.0×10 −12 to 3.2×10 −11 m 2/s results in an accurate fit with experimental results. The observed increase in the diffusion coefficient is likely due to a microstructural change on the length scale of the diffusing molecule, caused by the washing out of the glycerol. The glycerol content plays an important role in the structure development in the film when the films are produced. Based on SAXS results it is observed that films are formed in a phase-separating process, where a sponge-like structure is formed around glycerol domains. The results imply that the diffusion coefficient for salt in a film is a function of the initial glycerol content while preparing the film rather than the actual glycerol content during the permeation experiment. Furthermore, this sponge-like picture helps to understand the observed linear relation between the elastic modulus (EM) and the tensile strength (TS) of the films. The observations in this paper will contribute to control barriers, based on whey protein isolate, with respect to delayed or prolonged release of ingredients, brought into contact with an aqueous environment.

Diffusion of thiocyanate and hypothiocyanite in whey protein films incorporating the lactoperoxidase system

The diffusion of the thiocyanate (SCN −) and hypothiocyanite (OSCN −) components of a lactoperoxidase system (LPOS) in whey protein isolate (WPI) films was investigated. Diffusion coefficients for these molecules were measured for the LPOS-incorporated WPI films prepared with different WPI:glycerol ratios (1:1, 3:1, and 5:1). WPI film disks were coated on the surfaces of smoked salmon samples, and the samples were stored at 4, 10 and 22 °C. The diffusion coefficients were determined by fitting a mathematical model to the amounts of SCN − and OSCN − released from the disks during a period of time. The diffusion coefficients for SCN − ( D 1) and OSCN − ( D 2) in the films were 0.19–5.2 × 10 −12 m 2 s −1 and 0.13–6.5 × 10 −13 m 2 s −1, respectively. The D 1 and D 2 decreased as the WPI:glycerol ratio increased and the storage temperature decreased. The E a values for diffusion in 1:1, 3:1, and 5:1 WPI:glycerol films were 13.3, 29.5, and 35.6 kJmol −1, respectively, for SCN − and 15.8, 30.1, and 39.9 kJmol −1, respectively, for OSCN −.

Kinetics of Sucrose Crystallization in Whey Protein Films

The kinetics of sucrose crystallization in whey protein isolate (WPI) films was studied at 25 degrees C in four different relative humidity environments: 23, 33, 44, and 53%. The effects of protein matrix, crystallization inhibitors, and storage environment on the rate constants of sucrose crystallization were determined using the Avrami model of crystallization. It was found that a cross-linked, denatured whey protein (WP) matrix more effectively hindered sucrose crystallization than a protein matrix of native WP. The crystallization inhibitors tested were lactose, raffinose, modified starch (Purity 69), and polyvinylpyrrolidone (Plasdone C15). Raffinose and modified starch were determined to be the more effective inhibitors of sucrose crystallization. At lower relative humidities (23, 33, and 44%), the cross-linked protein matrix played a more important role in sucrose crystallization than the inhibitors. As relative humidity increased (53%), the crystallization inhibitors were more central to controlling sucrose crystallization in WPI films.

Temperature‐Sensitive Microcapsules Containing Lactoferrin and Their Action Against Carnobacterium viridans on Bologna

ABSTRACT: Lactoferrin (LF) was encapsulated in 2 types of emulsion to protect it from contact with agents like divalent cations, which interfere with its antimicrobial activity. First, paste‐like microcapsules were prepared as water‐in‐oil (W1/O) emulsions from mixtures of 20% w/v LF in distilled water, 20% w/v LF in 3% w/v sodium lactate or in 20 mM sodium bicarbonate, which were emulsified with an oil mixture of 22% butter fat plus 78% corn oil and 0.1% polyglycerol polyricinoleate. Second, freeze‐dried double emulsion (W1/O/W2), powdered microcapsules were produced following emulsification of paste‐like microcapsules in an external aqueous phase (W2) consisting of a denatured whey protein isolate (WPI) solution. The release of LF from the W1/O microcapsules was dependent on temperature and NaCl concentration. LF was not released from the W1/O emulsion at <5.5 °C. Its release was greater from W1/O microcapsules when suspended in 5% aqueous NaCl than in water at ≥10 °C, whereas LF release from freeze‐dried microcapsules was not controlled by temperature change. Paste‐like microcapsules were incorporated in edible WPI packaging film to test the antimicrobial activity of LF against a meat spoilage organism Carnobacterium viridans. The film was applied to the surface of bologna after its inoculation with the organism and stored under vacuum at 4 or 10 °C for 28 d. The growth of C. viridans was delayed at both temperatures and microencapsulated LF had greater antimicrobial activity than when unencapsulated. The temperature‐sensitive property of the W1/O microcapsules was reduced when they were incorporated into a WPI film.

Antimicrobial activity of whey protein based edible films incorporated with oregano, rosemary and garlic essential oils

Abstract The use of edible films to release antimicrobial constituents in food packaging is a form of active packaging. Antimicrobial properties of spice extracts are well known, however their application to edible films is limited. In this study, antimicrobial properties of whey protein isolate (WPI) films containing 1.0–4.0% (wt/vol) ratios of oregano, rosemary and garlic essential oils were tested against Escherichia coli O157:H7 (ATCC 35218), Staphylococcus aureus (ATCC 43300), Salmonella enteritidis (ATCC 13076), Listeria monocytogenes (NCTC 2167) and Lactobacillus plantarum (DSM 20174). Ten millilitres of molten hard agar was inoculated by 200 μl of bacterial cultures (colony count of 1 × 10 8 CFU/ml) grown overnight in appropriate medium. Circular discs of WPI films containing spice extracts, prepared by casting method, were placed on a bacterial lawn. Zones of inhibition were measured after an incubation period. The film containing oregano essential oil was the most effective against these bacteria at 2% level than those containing garlic and rosemary extracts ( P P

Tensile properties of compression-molded whey protein sheets: Determination of molding condition and glycerol-content effects and comparison with solution-cast films

Transparent glycerol (Gly)-plasticized whey protein isolate (WPI) sheets could be formed from Gly-WPI mixtures using compression molding, demonstrating that such mixtures display flowability and fusion behavior under certain conditions. The effects of glycerol content (GC), molding temperature and molding pressure on the tensile properties of the transparent compression-molded WPI sheets were studied, and the properties were compared to those of films produced using the solution-casting method. Compression-molding temperature and pressure did not significantly affect sheet stiffness (elastic modulus, EM), strength (tensile strength, TS) or extension (% elongation, %E) (p>0.05). Increasing the GC of compression-molded sheets decreased EM and TS, but had little effect on %E. The values of TS and %E of compression-molded WPI sheets with 40–50% GC were greater than those of solution-cast WPI films with 45% GC. These results indicate the possibility that Gly-WPI mixtures can be extruded into films for formation of edible or biodegradable wraps or heat-sealed pouches.

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.

Antimicrobial Effects of Lactoferrin, Lysozyme, and the Lactoperoxidase System and Edible Whey Protein Films Incorporating the Lactoperoxidase System Against Salmonella enterica and Escherichia coli O157:H7

ABSTRACT:Lactoferrin (LF), lysozyme (LZ), the lactoperoxidase system (LPOS), and edible whey protein isolate (WPI) films incorporating LPOS were studied for inhibition of Salmonella enterica and Escherichia coli O157:H7. Antimicrobial effects of LF (5 to 40 mg/mL), LZ (1 to 20 mg/mL), and LPOS (0.5% to 5.0% [w/v] [0.03–.25 g/g, dry basis]) were examined by measuring turbidity of antimicrobial‐containing media after inoculation and by examining cell inhibition by WPI films incorporating LPOS (LPOS‐WPI films) on an agar recovery medium. Elastic modulus (EM), tensile strength (TS), percent elongation (%E), oxygen permeability (OP), and Hunter L, a and b of WPI films incorporating 0.03 to 0.25 g/g of LPOS were compared with those of plain WPI films without LPOS. The growth of S. enterica and E. coli O157:H7 (4 log colony‐forming units [CFU]/mL) in tryptic soy broth (TSB) was not prevented by LF at ≥20 and ≥40 mg/mL, respectively. S. enterica and E. coli O157:H7 in TSB were not inhibited by LZ at ≥ 6 and ≥ 20 mg/mL, respectively. LPOS at concentrations of 2.75% (w/v) and 1.0% (w/v) reduced S. enterica and E. coli O157:H7 to below the limit of detection (1 CFU/mL) in TSB, respectively. LPOS‐WPI films (0.15 g/g) completely inhibited S. enterica and E. coli O157:H7 (4 log CFU/cm2), inoculated either onto agar before placing the film disc or onto top of the film disc. Incorporation of 0.25 g/g of LPOS decreased EM, TS, and %E. The oxygen barrier property of WPI films was improved with the incorporation of LPOS at 0.15 to 0.25 g/g.

Inhibition ofPenicillium communeby Edible Whey Protein Films Incorporating Lactoferrin, Lacto-ferrin Hydrolysate, and Lactoperoxidase Systems

ABSTRACT: Effects of lactoferrin (LF), lactoferrin hydrolysate (LFH), and lactoperoxidase systems (LPOS), both directly and incorporated into edible whey protein isolate (WPI) films, on the inhibition of Penicillium commune were studied. Mechanical, oxygen-barrier, and color properties of WPI films with and without LPOS were also compared. Antimicrobial effects were examined by turbidity, disc diameter, surface spreading, and film surface inoculation tests. Film elastic modulus, tensile strength, percent elongation, oxygen permeability, and Hunter L, a, and b values were tested. LF and LFH at 10 mg/mL or higher inhibited P. commune in 1% peptone water but not in potato dextrose broth. WPI films incorporating LPOS inhibited growth of P. commune. The properties of WPI films were not significantly changed by incorporation of LPOS (P > 0.05).

Mechanical Properties of Heat-cured Whey Protein-based Edible Films Compared with Collagen Casings under Sausage Manufacturing Conditions

ABSTRACT: Edible films were produced using whey protein isolate (WPI) (5%, w/v), glycerol (3.3%, w/v) and candelilla wax (0.8%, w/v). One set of films was heat cured at 90°C for 12 h and another at 80°C for 24 h. WPI-based films, together with collagen films, were put through a meat-processing scheme typical of Polish sausage manufacture. Meat-processing conditions were stage 1: 57°C/60 min/36% RH; stage 2: 65°C/90 min/60% RH; and stage 3: 77°C/30 min/80% RH. Effects of meat-processing conditions on mechanical properties: tensile strength (TS), elongation (%E), and apparent modulus (AM) were determined. All films remained intact throughout the process. TS, %E, and AM of collagen films did not change during the multistage cooking process. The %E of heat-cured WPI films was similar to that of collagen films and also did not change during the cooking stages. The TS and AM of both heat-cured WPI-based films were initially lower than collagen films and continued to decline during the cooking stages. TS and AM of both films at the end of cooking were lower (P < 0.05) than films that did not go through the multistage cooking process.

Water Solubility, Mechanical, Barrier, and Thermal Properties of Cross‐linked Whey Protein Isolate‐based Films

ABSTRACTWater solubility, hermal properties, tensile strength, percent elongation, oxygen permeability (OP), water‐vapor permeability (WVP) of cross‐linked glycerol plasticized whey protein isolate films were studied to determine the effect of cross‐linkers (glutaraldehyde, formaldehyde, dialdehyde starch, carbonyldiimidazole, and UV irradiation) on film properties. With the exception of UV treatment, solubility of the films decreased (P&gt;0.05) upon treatment of the film‐forming solutions with chemical cross‐linkers. Tensile strength increased (P&gt;0.05), whereas percent elongation was not affected by cross‐linking. Chemical cross‐linking increased (P&gt;0.05) WVP and decreased (P&gt;0.05) OP of the films. UV treatment had no effect on WVP and O P. With the exception of UV‐treated films, both onset temperature and degradation temperatures, as determined by differential scanning calorimetry, were increased upon cross‐linking.

Physical properties and sensory evaluation of WPI films of varying thickness

The effect of varying thickness on the water barrier properties, tensile properties and sensory characteristics of glycerol-plasticised whey protein isolate (WPI) films was investigated. Thickness was varied by preparing films with increasingly dilute film forming WPI solutions in the range 9.5–2.3 g protein/100 g. All films had a glycerol to protein ratio of 0.37 (Gly: Pro). Tensile strength (TS), elastic modulus (EM) and film permeance were unaffected by film thickness but maximum load (ML) and % elongation (E) decreased ( P<0.05) with decreasing thickness. In a sensory test with crackers and melted cheese, panelists could readily detect the thickest films (79 μm) but not the thinnest films (23 μm) ( P<0.05). The results indicate that reducing the thickness of glycerol plasticised WPI films makes them less perceptible in a food system while maintaining moisture barrier and certain tensile properties.

Effect of processing on the displacement of whey proteins: applying the orogenic model to a real system.

Atomic force microscopy (AFM) has been used to investigate the displacement of a commercial whey protein system and the behavior as compared to that of beta-lactoglobulin (Mackie, A. R.; Gunning, A. P.; Wilde, P. J.; Morris, V. J. Orogenic displacement of protein from the air-water interface by competitive adsorption. J. Colloid Interface Sci. 1999, 210, 157-166). The whey protein isolate (WPI) was displaced from an air-water interface by the surfactants Tween 20 and Tween 60. Displacement data obtained were compared with data obtained for pure beta-lactoglobulin and have shown that WPI was more resistant to displacement from the air-water interface than native beta-lactoglobulin. This was related to the greater surface elasticity of WPI at higher surface stresses. In the presence of Tween 20, WPI was observed to remain on the interface at surface pressures up to 8 mN/m greater than the surface pressure at which complete displacement of beta-lactoglobulin was observed. Displacement of WPI and beta-lactoglobulin films by the surfactant Tween 60 showed similar results. However, because of the lower surface activity of Tween 60, it was not possible to reach surface tension values similar to those obtained for Tween 20. Despite the lower surface activity of Tween 60, WPI was still observed to be present at the interface at surface pressure values greater than those by which beta-lactoglobulin had been completely displaced.

Barrier and mechanical properties of milk protein-based edible films containing nutraceuticals.

Calcium caseinate (CC) and whey protein isolate (WPI) films were prepared to contain 5 or 10% Gluconal Cal (GC), a mixture of calcium lactate and gluconate, or 0.1 or 0.2% alpha-tocopheryl acetate (VE), respectively. The pH and viscosity of film-forming solutions and the water vapor permeability and tensile property of the films were determined using standard procedures. CC and WPI films have the capabilities to carry high concentration of GC or VE, but some of the film functionality might be compromised. Adding VE to CC and WPI films increased film elongation at break, whereas incorporating 0.2% VE decreased WVP of CC films and tensile strength of both CC and WPI films. Incorporation of GC reduced the tensile strength of CC films (P < 0.05), with 10% GC decreasing both elongation at break and WVP (P < 0.05). These types of films may be used for wrapping or coating to enhance the nutritional value of foods. The concentration of GC and VE added to the films must be carefully selected to meet required water barrier and mechanical properties of the films depending on their specific applications.

Efecto de la temperatura sobre películas de un aislado proteico del suero bovino (WPI) adsorbidas sobre la interfase aceite-agua

Heat-induced interfacial aggregation of a whey protein isolate (WPI) with a high content of β-lactoglobulin, previously adsorbed at the oil-water interface, was studied by interfacial dynamic characteristics (interfacial tension and surface dilational properties) performed in a automatic drop tensiometer coupled with microscopic observation and image analysis of the drop after heat-treatment. The temperature, ranging between 20 and 80 oC, and protein concentration in aqueous bulk phase, ranging between 1.10 -1 and 1.10 -5 % wt/wt, were studied as variables. The pH, and ionic strength were maintained constant at 5 and 0.05 M, respectively. During the heat-treatment, WPI films behave typically as viscoelastic with non-zero phase angle, but with increasing elastic characteristics as the heat-treatment progresses. During isothermal treatment the surface dilational modulus, E, increases and the interfacial tension, σ, and phase angle, φ, decrease with time to a plateau value. The time dependence of E can be quantified by a first-order equation according to two kinetic mechanisms. The rate of thermal changes in WPI adsorbed films increases with protein concentration in solution. Heat-treatment produces irreversible changes in WPI adsorbed films because the interfacial characteristics do not return to original values after cooling back to the initial temperature. Significant changes in interfacial characteristics and drop image associated with interfacial WPI gelation were observed at protein concentration as low as 1.10 -5 % wt/wt, even for heat-treatment at 40 oC.

Improved water vapor barrier of whey protein films by addition of an acetylated monoglyceride

This study aimed to determine to what extent the water-vapor barrier of whey protein isolate (WPI) films could be improved by adding a lipid and make laminate and emulsion films. The laminate whey protein–lipid film decreased the water vapor permeability (WVP) 70 times compared with the WPI film. The WVP of the emulsion films was half the value of the WPI film and was not affected by changes in lipid concentration, whereas an increased homogenization led to a slight reduction in WVP. The mechanical properties showed that the lipid functioned as an apparent plasticizer by enhancing the fracture properties of the emulsion films. This effect increased with homogenization. The maximum strain at break was 117% compared with 50% for the less-homogenized emulsion films and 20% for the pure WPI films. Phase-separated emulsion films were produced with a concentration gradient of fat through the films, but pure bilayer films were not formed.

Effect of soya oil and glycerol on physical properties of composite WPI films

The water vapour permeability (WVP), mechanical strength, equilibrium moisture content (MC), glass transition temperature and opacity of whey protein isolate films plasticised with different levels of glycerol (Gly) (glycerol:protein (Gly:Pr)=0.5, 0.6 and 0.7) and containing different levels of added soya oil (oil:protein (Oil:Pr) ratio=0.0, 0.2, 0.3 and 0.4) were measured. Increasing oil concentration led to increases in percent elongation (EL), glass transition ( T g) temperature, and decreases in MC, tensile strength (TS), and elastic modulus (EM), but did not affect the WVP of films. Increasing levels of Gly led to increases in percent EL, MC and decreases in TS, EM, T g and film opacity.