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During storage of heat-treated acidic (pH ≤ 4.6) whey protein beverages, formation of protein aggregates can create undesirable turbidity and sedimentation. In this study, we found that a slow protein aggregation process controlled the rate of formation of sediment and turbidity. A heat-treated model beverage containing 12.5 g/L whey protein at a pH of 4 was stored for 6 wk at 3 different storage temperatures and analyzed for turbidity, soluble protein, and protein aggregates. One sample was stored without further treatment and the other sample was filtered to remove protein aggregates formed during heating. This was done to test the hypothesis that aggregates formed during heat treatment served as nuclei for deposition of soluble protein. Turbidity increased and soluble protein decreased as protein aggregates formed during storage. Increasing the storage temperature accelerated this process. The loss of soluble protein during storage was fit to first- and second-order kinetic equations, allowing the prediction of the effect of protein concentration, storage time, and storage temperature on the formation of protein aggregates. [ABSTRACT FROM AUTHOR]

Biodegradable titanium dioxide (TiO2)/whey protein isolate (WPI) blend films were made by casting denatured WPI film solutions incorporated with TiO2 nanoparticles. X-ray diffraction, UV-vis spectra, and fluorescence spectra of the films showed the successful incorporation of TiO2 nanoparticles into the WPI matrix and indicated the interactions between TiO2 and WPI. Mechanical tests revealed the antiplasticizing effect of TiO2 nanoparticles on the WPI/TiO2 film. Small amounts (<1 wt%) of added TiO2 nanoparticles significantly increase the tensile properties of WPI film, but also decrease the moisture barrier properties. The addition of higher amounts (>1 wt%) of TiO2 improves moisture barrier properties but lowers the tensile properties of the film. Microstructural evaluation confirmed the aggregation and distribution of TiO2 nanoparticles within the WPI matrix and validated the results of functional properties of the WPI/TiO2 film. [ABSTRACT FROM AUTHOR]

Use of hydrolyzed proteins is known to delay hardening of high-protein nutrition bars. Bars were formulated using ratios of 0%, 25%, 50%, 75%, or 100% partially hydrolyzed whey protein isolate (HWPI) to nonhydrolyzed whey protein isolate (WPI) in one experiment, and either WPI or HWPI combined with high-fructose corn syrup (HFCS) or sorbitol syrup (SS) in a 2nd experiment along with vegetable shortening such that initial aw was 0.59 for HWPI bars and 0.64 for WPI bars. After mixing, the dough was extruded into bars and stored at 32 °C for accelerated shelf-life testing. Hardness, color, and microstructure were measured during 42 d of storage. Bars initially had similar hardness of approximately 3.4 N that increased during storage. Bars with HWPI were softest with hardness at 37 d of 10 to 15 N compared to almost 100 N for bars with WPI. Water activity increased for WPI bars to 0.69 by 34 d. Bars became darker during storage depending on amount of Maillard browning reactants, that is, HWPI/HFCS bars ≫ HWPI/SS > WPI/HFCS bars > WPI/SS bars. Bar microstructure at day 2 showed protein and fat dispersed in particulate form throughout the carbohydrate syrup within the bar matrix. During storage, a single nonlipid phase developed in HWPI bars while in WPI bars a phase separation occurred between protein and carbohydrate. We propose that such phase separation initiates bar hardening and promotes subsequent protein aggregation. Successful formulation of HPN bars depends on cosolvent properties of the polyol/sugar toward the proteins and their preferential exclusion from the solvation layer surrounding the proteins. PRACTICAL APPLICATION: High-protein nutrition bars can be formulated so they remain soft during storage by selecting proteins and sugars that are compatible with each other. Otherwise, the protein and sugar will separate from each other which can then lead to hardening. [ABSTRACT FROM AUTHOR]

Ultrafiltration is widely used to concentrate proteins, but fractionation of one protein from another is much less common. This study examined the use of positively charged membranes to increase the selectivity of ultrafiltration and allow the fractionation of proteins from cheese whey. By adding a positive charge to ultrafiltration membranes, and adjusting the solution pH, it was possible to permeate proteins having little or no charge, such as glycomacropeptide, and retain proteins having a positive charge. Placing a charge on the membrane increased the selectivity by over 600% compared to using an uncharged membrane. The data were fit using the stagnant film model that relates the observed sieving coefficient to membrane parameters such as the flux, mass transfer coefficient, and membrane Peclet number. The model was a useful tool for data analysis and for the scale up of membrane separations for whey protein fractionation. [ABSTRACT FROM AUTHOR]

The impact of agglomeration on flavor and flavor stability of whey protein concentrates 80% (WPC80) and whey protein isolates (WPI) has not been widely addressed. This study examined the impact of agglomeration on the flavor and flavor stability of commercial WPC80 and WPI across 18 mo of storage. Duplicate agglomerated and nonagglomerated WPC80 and WPI were collected from 4 facilities and stored at 21 °C, 50% relative humidity. Volatile analysis using solid phase microextraction (SPME) with gas chromatography-mass spectrometry (GC-MS) and descriptive sensory analysis were conducted every 2 mo. Solubility index, bulk volume, dispersibility, moisture, and color ( L, a, b) were tested every 3 or 6 mo. Consumer acceptance testing with protein beverages was conducted with fresh and stored whey proteins. Higher intensities and more rapid development of lipid oxidation flavors (cardboard, raisin/brothy, cucumber, and fatty) were noted in agglomerated powders compared to nonagglomerated powders ( P < 0.05). Volatile analysis results confirmed sensory results, which indicated increased formation of aldehydes and ketones in agglomerated products compared to nonagglomerated powders ( P < 0.05). Consumer acceptance scores for protein beverages were lower for beverages made with agglomerated WPC80 stored for 12 mo and agglomerated or nonagglomerated WPI stored for 18 mo compared to fresh products while trained panelists detected differences among beverages and rehydrated proteins earlier. Agglomeration with or without lecithin decreased the storage stability of whey proteins. These results indicate that the optimum shelf life at 21 °C for nonagglomerated whey proteins is 12 to 15 mo and 8 to 12 mo for agglomerated whey proteins. [ABSTRACT FROM AUTHOR]

The effect of the application of whey protein isolate (WPI) solution as a postbreading dip to reduce oil absorption in deep-fried, battered, and breaded chicken patties on sensory properties was investigated. Chicken patties were battered, breaded with either crackermeal (CMP) or Japanese breadcrumbs (JBP), and dipped into WPI solutions at varying protein concentrations (0%, 2.5%, 5%, and 10%[w/w] WPI) and pH levels (pH 2, 3, and 8). A trained descriptive sensory panel evaluated the patties for 16 attributes relating to appearance, texture, and flavor. Instrumental analysis on the color and texture of the patties was also performed. The only perceivable changes in treated patties were related to color, hardness, and crunchiness. Increasing WPI concentration caused darkening of JBP but made CMP lighter. Patties treated at pH 8 were significantly darker across all WPI concentrations. The presence of WPI increased hardness and crust fracture for CMP but not JBP. Variations in pH levels did not affect texture. Thus, JBP that showed the highest lipid reduction (10% WPI at pH 2) were observed to be darker, less yellow, but did not produce any perceivable changes in hardness or crunchiness, while CMP with the lowest lipid content (5% WPI at pH 2) were lighter, more yellow, harder, and crunchier. [ABSTRACT FROM AUTHOR]

The formations of glycerol (Gly)-plasticized whey protein isolate (WPI)–hydroxypropylmethylcellulose (HPMC) films, blended using different combinations and at different conditions, were investigated. The resulting WPI: Gly-HPMC films were analyzed for mechanical properties, oxygen permeability (OP), and water solubility. Differences due to HPMC quantity and blend method were determined via SAS software. While WPI: Gly and HPMC films were transparent, blend films were translucent, indicating some degree of immiscibility and/or WPI–HPMC aggregated domains in the blend films. WPI: Gly-HPMC films were stronger than WPI: Gly films and more flexible and stretchable than HPMC films, with films becoming stiffer, stronger, and less stretchable as the concentration of HPMC increased. However, WPI: Gly-HPMC blended films maintained the same low OP of WPI: Gly films, significantly lower than the OP of HPMC films. Comparison of mechanical properties and OP of films made by heat-denaturing WPI before and after blending with HPMC did not indicate any difference in degree of cross-linking between the methods, while solubility data indicated otherwise. Overall, while adding HPMC to WPI: Gly films had a large effect on the flexibility, strength, stretchability, and water solubility of the film polymeric network, results indicated that HPMC had no effect on OP through the polymer network. WPI–HPMC blend films had a desirable combination of mechanical and oxygen barrier properties, reflecting the combination of hydrogen-bonding, hydrophobic interactions, and disulfide bond cross-linking in the blended polymer network. [ABSTRACT FROM AUTHOR]

Whey protein-based edible coating was used to reduce oxidative degradation and microbial growth of low-fat sausages (LFSs) stored at 4 °C for 8 wk, under aerobic package. Whey protein coating reduced ( P < 0.05) thiobarbituric acid-reactive substances (TBARS) and peroxide value (PV) formation compared to control sausages. The percent inhibition of TBARS and PV for whey protein-coated sausages, compared to the control, was 31.3% and 27.1%, respectively. The ability of the whey protein coating to provide a moisture barrier for the sausages was reduced ( P < 0.05). In addition, a reduction of moisture loss by 36.7% compared to the control was achieved by whey coating. However, whey protein coating of LFSs did not inhibit the growth of either the total number of aerobic bacteria or of Listeria monocytogenes. These results indicated that whey protein coating had an antioxidative activity in LFSs under aerobic package during refrigerated storage. [ABSTRACT FROM AUTHOR]

Harvested chestnut is characterized by a short shelf life, exposing many Chinese producers to a storage problem as product losses are very high. The objective of this study was to develop a suitable technology to extend the shelf life of harvested chestnut fruits for commercial use. The effect of whey protein isolate–pullulan (WPI–Pul) coating on fresh-roasted chestnuts (FRC) and roasted freeze-dried chestnut (RFDC) quality and shelf life was studied under 2 different storage temperature (4 and 20 °C) conditions. Coatings were formed directly onto the surface of the fruits by dipping them into a film solution. SEM micrographs showed homogeneous WPI–Pul to cover the whole surface of chestnut with good adherence and perfect integrity. Moisture loss or gain, fruit quality, and shelf life were evaluated by weight loss or gain, surface color development, and visible decay during the storage period of 15 to 120 d at 4 and 20 °C, respectively. WPI–Pul coating had a low, yet significant effect on reducing moisture loss and decay incidence of FRC, hence delaying changes in their external color. The results were satisfactory when the coating was done with freeze-drying at low temperature storage, thus improving the quality and increasing the shelf life. This provides an alternative strategy to minimize the significant losses in harvested chestnut. [ABSTRACT FROM AUTHOR]

The effects of glycerol and moisture contents on the thermal transitions of whey protein isolate (WPI) powder–glycerol–water mixtures were studied. Mixtures with ratios of 100:0, 70:30, 60:40, and 50:50 WPI:glycerol on a dry basis (db) were preconditioned to 0.34 ± 0.01 (25.4 ± 0.4 °C) and 0.48 ± 0.02 (25.9 ± 2.2 °C) water activity. Differential scanning calorimetry (DSC) showed the existence of an endothermic peak starting at 148.3 ± 0.7 °C for 100% WPI preconditioned to a water activity of 0.34 ± 0.01. The onset temperature of this peak decreased with addition and increase of glycerol content, as well as with the increase in water activity from 0.34 ± 0.01 to 0.48 ± 0.02. An additional endothermic transition, important for extruding the mixtures into flexible sheets, occurred in mixtures containing 50% glycerol db, preconditioned to 0.48 ± 0.02 water activity. The onset temperature of the peak was 146 ± 2.0 °C. Whey protein-based sheets containing 45.8%, 48.8%, and 51.9% glycerol db were obtained using a Haake–Leistritz corotating twin-screw extruder. All samples were obtained at a screw speed of 250 rpm and a final barrel-temperature profile of 20, 20, 20, 80, 110, and 130 °C. Melt temperature at the time of sheet formation was 143 to 150 °C. Average thickness of the sheets was 1.31 ± 0.02 mm. Samples with 45.8% glycerol db had significantly higher tensile strength (TS) than samples with higher glycerol contents. Also, as glycerol concentration increased, sheet elastic modulus (EM) decreased significantly ( P≤ 0.05). Extrusion of whey protein-based sheets is an important step toward extrusion of thinner edible films for food wraps, layers, or pouches. [ABSTRACT FROM AUTHOR]

BSTRACT: The 2 main storage proteins of soy-glycinin (11S) and β-conglycinin (7S)-exhibit unique behaviors during processing, such as gelling, emulsifying, or foaming. The objective of this work was to observe the interactions between soy protein isolates enriched in 7S or 11S and whey protein isolate (WPI) in oil-water emulsion systems. Soy oil emulsion droplets were stabilized by either soy proteins (7S or 11S rich fractions) or whey proteins, and then whey proteins or soy proteins were added to the aqueous phase. Although the emulsifying behavior of these proteins has been studied separately, the effect of the presence of mixed protein systems at interfaces on the bulk properties of the emulsions has yet to be characterized. The particle size distribution and viscosity of the emulsions were measured before and after heating at 80 and 90 °C for 10 min. In addition, SDS-PAGE electrophoresis was carried out to determine if protein adsorption or exchanges at the interface occurred after heating. When WPI was added to soy protein emulsions, gelling occurred with heat treatment at WPI concentrations >2.5%. In addition, whey proteins were found adsorbed at the oil-water interface together with 7S or 11S proteins. When 7S or 11S fractions were added to WPI-stabilized emulsions, no gelation occurred at concentrations up to 2.5% soy protein. In this case also, 7S or 11S formed complexes at the interface with whey proteins during heating. [ABSTRACT FROM AUTHOR]

The article presents a study which examined the effect of mechanical roughening of commercially blanched-and -roasted peanuts on whey protein coating efficiency. Increased coating coverage varied among peanuts possibly due to variable change of peanut surfaces during commercial processing and storage before coating. The effect of roughening, as well as the disruption of the parenchyma cell structure of peanuts was confirmed by scanning electron microscope (SEM) micrographs of treated peanuts.

The article presents a study which evaluated the effects of whey permeate (WP)-based medium and harvesting time on the proximate composition of Lentinus edodes mycelia. The researchers determined the biomass production, mineral profile, ash content, crudewater-soluble polysaccharide (WSP), and crude protein content for Lentinus edodes mycelia grown on WP-based medium. The main component found in the ash of mushroom mycelia was potassium, followed by phosphorus, sodium, calcium, and magnesium.

The article presents a study which developed a sensory lexicon for whey and soy proteins and compared their sensory properties. Results showed that all protein products had the minimum required protein content. Differences among and between sensory properties of whey and soy proteins were found. A survey conducted among consumers suggested that dairy products were generally perceived as better tasting than soy products.

BSTRACT: The objective of this work was to develop a process to fractionate proteins from lactic acid whey, which is underused compared with sweet whey, using food-grade buffers and cation-exchange chromatography. Bound proteins were desorbed either all at once to make whey protein isolate (WPI), or in 2 steps to 1st make α-lactalbumin (ALA) and then WPI depleted in ALA. Recovery and purity using lactic acid whey were comparable to previously reported processes using sweet whey. Capacity and throughput were slightly lower using lactic acid whey. This research provides a basis for adding value to the 6 million metric tons of lactic acid whey produced annually in the United States. [ABSTRACT FROM AUTHOR]

BSTRACT: Edible coatings from whey protein isolate (WPI)-beeswax (BW) were made with various total solid (8%, 12%, 16%, 20%) and BW content (0%, 20%, 40%, 60%, dry bases). Apple pieces were coated with the emulsion coatings; weight loss and color (CIE L*, a*, b*, and browning index [BI]) were measured during storage. Results show that coated apples had higher L* and presented lower BI than uncoated apples, indicating that whey proteins exert an antibrowning effect. The BI decreased as the solid content of the coating emulsions increased. Increasing BW content decreased enzymatic browning. Coating application did not reduce weight loss in fresh-cut apples, probably due to the product's high relative humidity. [ABSTRACT FROM AUTHOR]

BSTRACT: Films were formed from heated whey protein isolate (WPI) solutions (heated [H] films) and from unheated WPI solutions following adjustment to pH 11, with subsequent readjustment to pH 7 (unheated, readjusted [UR] films) or without readjustment to pH 7 (unheated, unadjusted films [UU] films). UU and UR films had significantly lower % elongation, tensile strength, and Young's modulus than H films. Film solubility and dispersion in water were in the order: H films < UU films < UR films. Free sulphydryl groups were lower and disulphide-mediated polymerization was higher in heated than in unheated WPI solutions whereas solubility of H films increased in the presence of dithiothreitol. [ABSTRACT FROM AUTHOR]

BSTRACT: Angel food cakes made from egg white or whey protein foams were compared. Cakes were evaluated based on final volume, dynamic volume change, and rheological transitions during baking. Cake expansion during baking was a function of protein concentration regardless of protein type. Cakes containing whey proteins had a lower ability to prevent collapse once starch gelatinization started during baking. Heat-treating whey proteins or adding xanthan gum increases cake volume, but not to the extent of egg-white proteins. Cakes containing egg-white proteins became more elastic at 60 to 85 °C than those containing whey proteins, indicating physical differences in the heat-set protein foam network associated with protein type. [ABSTRACT FROM AUTHOR]

BSTRACT: Transglutaminse (TGase)-catalyzed interactions of whey (WPI)/myofibrillar (MPI) protein isolates were investigated under 5 conditions: (1) ionic strengths; (2) calcium/ethylenediaminetetra-acetic acid (EDTA); (3) enzyme:substrate ratio; (4) WPI:MPI ratio; and (5) preheating of WPI (80 °C). TGase treatments of MPI in distilled water converted myosin heavy chain and actin into lower-molecular-weight polypeptides. The reaction, accelerated by the presence of WPI but diminished by NaCl, was completely reversed upon extended incubation. There was no visible WPI/MPI cross-linking; and the enzyme:substrate or WPI:MPI ratio, preheating, calcium, and EDTA did not influence the enzyme reaction. TGase treatment did not alter the melting pattern of WPI/MPI mixtures, but markedly enhanced their thermal gelling ability. [ABSTRACT FROM AUTHOR]

BSTRACT: The objective of this work was to observe the microstructure of feta cheese using confocal scanning laser microscopy. Low fat cheese and cheese containing capsule-producing cultures were made. The protein network was observed using the reflectance mode of the confocal microscope. Fat was stained by Nile red dye diluted with whey. More even distribution of fat with a larger number of smaller globules was observed in cheese made with noncapsule-forming culture compared to that made with the capsule-forming culture. Nonfat cheese had compact structure when made with noncapsule-forming culture which contrasted with the open structure observed in cheese made with the capsule-forming culture [ABSTRACT FROM AUTHOR]

BSTRACT: The dissolution kinetics and mechanical properties of whey protein concentrate (WPC) gels were investigated as part of a general study on cleaning mechanisms of milk fouling. The dissolution results showed that the WPC gel is a suitable model material to simulate milk fouling and the dissolution process is a major factor controlling the cleaning process. The hardness, elastic modulus, and fracture load of the WPC gels decreased significantly when they were treated with alkaline solution, indicating that certain physical and chemical changes occurred in these treated gels; as a result, different dissolution rates were observed. The results obtained in this article provide a good foundation for further studies on the cleaning mechanisms of milk fouling using WPC gels. [ABSTRACT FROM AUTHOR]

BSTRACT Whey protein concentrate (WPC, 80% protein) was textured using thermoplastic extrusion to produce textured whey protein (TWP). Binding agents were investigated for their usefulness in the formation of a TWP meatless patty. Sensory analysis of 2 TWP patty formulations and a commercially available textured vegetable protein (TVP) patty was performed. Patties were evaluated on appearance, texture, flavor, aftertaste and overall acceptance. There were no significant differences among the appearance and texture of the 3 patties, whereas the flavor, aftertaste and overall acceptance were significantly different. Sensory analysis demonstrated that TWP patties were as acceptable as the commercial TVP patty. [ABSTRACT FROM AUTHOR]

We extruded a dry mix of 2 parts whey protein concentrate (80% protein) and 1 part cornstarch using water, 0.1 N HCl, or 0.2 M NaOH as the liquid, or adding calcium (1.69% w/w) to the dry mix with water as the liquid. The functionality and acceptability of textured whey protein (TWP) extrudates was determined. Ground beef patties containing up to 40% (w/w) of hydrated TWP extrudates made with base (TWPbase) were as acceptable to a consumer panel as all beef patties. Additionally, patties containing 40% (w/w) TWPbase incurred less cook loss and less diameter reduction after cooking, but were less cohesive than all beef patties. [ABSTRACT FROM AUTHOR]

Lactoferrin (LF) in colostral whey was isolated by anti-LF immunoglobulin in yolk (IgY)-Sepharose 4B immunoaffinity chromatography, and parameters such as binding capacity (qm) and dissociation constant (Kd, 10-6 M) of this immunoaffinity gel for LF were discussed. Purification folds for colostral whey I (from colostrum collected within 6 d of postpartum) and colostral whey II (from colostrum collected within 1 d of postpartum) by anti-LF IgY-immunoaffinity chromatography were 135.80 and 103.60, respectively. The recovery for LF in the same colostral whey sample by anti-LF IgY-immunoaffinity chromatography was 82 to 99 %. qm of anti-LF IgY-immunoaffinity gel for LF in colostral whey I and whey II were 0.372 and 0.272 mg LF/mL wet gel, respectively. Kd of anti-LF IgY-immunoaffinity gel for LF in colostral whey I was 1.594 x 10-6 M and II was 1.587 10-6 M. [ABSTRACT FROM AUTHOR]

BSTRACT: Proteins from defatted Gevuina avellana seeds were extracted in aqueous media. Protein extraction was limited at liquid-to-solid ratios under 12 g/g, but was not significantly affected by temperatures in the 25 to 45 °C range. The maximum protein extractability occurred both at acidic and alkaline pH; the presence and concentration of NaCl affected it differently, depending on the extraction pH. Up to 3 extraction stages with whey recycle after ultrafiltration were performed, without affecting the protein extraction yield. The functional properties of the protein isolated with membranes were similar or better than those from isoelectric precipitation. [ABSTRACT FROM AUTHOR]

Whey protein isolate (WPI)-based edible biopolymer films were prepared using a film-forming stage designed to provide heat-induced gelation. Effects of whey-protein ratios, calcium, glycerol (plasticizer), and emulsion droplet incorporation on film tensile and barrier properties were investigated. Protein ratios had less influence on tensile strength, elongation, and water vapor permeability than glycerol and calcium ion concentrations. Semitransparent films with reasonably high tensile and UV-light barrier properties and moderate water vapor barrier properties were prepared from WPI:20% glycerol:10 mM calcium solutions. Microstructure analysis revealed the influence of glycerol and calcium concentrations on gel networks, which could be related to film tensile properties. [ABSTRACT FROM AUTHOR]

The particle size and zeta potential of model beverage emulsions (0.01 wt% soybean oil-in-water emulsions, d ≈ 1 mm) stabilized by gum arabic, modified starch, or whey protein isolate (WPl) were studied with varying pH CaCl2 to 9), CaCl2 concentration (0 to 25 mM), and temperature (30 °C to 90 °C). Temperature, pH, CaCl2 strongly influenced emulsions stabilized by WPl because its stabilizing mechanism was mainly electrostatic repulsion, but not those stabilized by gum arabic or modified starch because their stabilizing modes of action were mainly steric repulsion. This study may have important implications for the application of WPl as an emulsifier in beverage emulsions. [ABSTRACT FROM AUTHOR]

Proteins/polysaccharides complexes could improve emulsifying properties of proteins by thickening the layer at the interface of the oil droplets. Emulsifying properties of whey protein-carboxymethylcelluiose complexes (WPl/CMC) were compared with those of a whey protein isolate (WPl). Ingredients were incorporated into oil-in-water emulsions with various protein and off contents. Visual observations, protein load, protein distribution and rheological measurements were used to evaluate emulsion stability. Protein load up to 26.1 and 48.9 mg protein/g oil were obtained for WPI and WPl/CMC emulsions, respectively. The higher protein load of WPl/CMC emulsions and visual observations indicated that WPI/CMC complexes had greater emulsifying properties against coalescence than whey proteins. However, complexes enhanced flocculation of oil droplets. [ABSTRACT FROM AUTHOR]

From 5% w/v whey protein isolate (WPI), whey protein/lipid emulsion edible films were produced that were sorbitol- or glycerol-plasticized, containing butterfat (0.2% w/v) or candelilla wax (0.8% w/v). Thermal properties of the films determined by Differential Scanning Calorimetry (DSC) showed onset temperatures (To) of 126 to 127 °C for sorbitol- and 108 to 122 °C for glycerol-plasticized films. To values were used as the basis for heat sealing temperatures. Temperature (110, 120, 130 °C], pressure (296, 445 kPa), and dwell time (1, 3 s) affected seal strength. Optimum heat sealing temperature was 130 °C for sorbitol- and 110 °C for glycerol-plasticized films. All films were heat sealable with an impulse heat-sealer. Electron Spectroscopy for Chemical Analysis (ESCA) of the surfaces of both sealed and unsealed films showed increase in hydrogen and covalent bonds involving C-O-H and N-C, which may be the main forces responsible for the sealed joint formation of the films. [ABSTRACT FROM AUTHOR]

Low pH (5.2) whey protein isolate-based edible films containing p-aminobenzolc acid (PABA) or sorbic acid (SA) were developed and assessed for Inhibition of Listeria monocytogenes, Escherichia coil O157:H7, and Salmonella Typhimurium DT104 in a disc diffusion assay. Water vapor permeability (WVP), tensile strength (TS), and percent elongation (%E) were also determined. Using 1.5% PABA and SA, average Inhibition zone diameters were 21.8, 14.6, 13.9, and 26.7, 10.5, 9.7 mm for L. monocytogenes, E. coli O157:H7, and S. Typhimurium DT104, respectively. Three strains of S. Typhimurium DT104 were resistant to 0.5% SA. Addition of PABA and SA increased %E, but decreased TS. WVP was not affected by 0.5% and 0.75% SA; however, PABA increased WVP. [ABSTRACT FROM AUTHOR]

Color analysis on apple and potato slices coated with calcium caseinate or whey protein solutions showed that the 2 coatings efficiently delayed browning by acting as oxygen barriers. The antioxidant properties of the films were realized using a model allowing the release of oxidative species by electrolysis of saline buffer. Whey proteins were a better antioxidant capacity than calcium caseinate. Furthermore, addition of carboxymethyl cellulose (CMC) to the formulations significantly improved their antioxidative power. Best scavenging of oxygen free radicals and reactive oxygen species was found for films based on whey proteins and CMC which inhibited by 75% the formation of colored compounds produced by the reaction of the oxidative species with N,N-diethyl-p-phenylenediamine. [ABSTRACT FROM AUTHOR]

Gelation properties of 4 major protein additives were measured with and without salt during various hydration times. As hydration time increased, stress and strain of beef plasma and egg white gradually decreased regardless of salt. Unsalted whey proteins did not form a gel until the hydration time reached 48 h. Stress values of salted beef plasma with no hydration were significantly high. Soy protein isolate did not form a measurable gel at 9% concentration regardless of the presence of salt under rheological instruments, however its denaturation temperature was detected under DSC. Effect of salt on gel color was more pronounced with whey protein concentrate. [ABSTRACT FROM AUTHOR]

The antioxidant capabilities of whey in a Tween 20™-stabilized salmon emulsion were investigated. Whey fractions inhibited formation of thiobarbituric acid reactive substances (TBARS) and lipid peroxides in a 10 % salmon oil emulsion in the order of whey > high-molecular-weight (HMW) fraction > low-molecular-weight fraction. Heating the HMW fraction exposed sulfhydryls, with optimum exposure at 80 °C. Heating the HMW fraction above 80 °C increased antioxidant activity. The HMW fraction of whey (80 °C) alone, α-tocopherol (40 ppm) alone, and their combination inhibited TBARS 59, 19 and 86%, respectively, at 21 d of storage. Sulfhydryls oxidized before α-tocopherol, suggesting that sulfydryls are the primary antioxidant. Results indicate that whey proteins could be useful antioxidants in food emulsions. [ABSTRACT FROM AUTHOR]

The yellowing rates of edible coatings were determined at 23, 40, and 55 °C at 75% relative humidity (RH). Whey protein isolate (WPI) coatings had lower yellowing rates than whey protein concentrate (WPC) and the same rates as shellac coatings. Hydroxypropyl methylcellulose (HPMC) coatings had the lowest yellowing rates. Zein coatings became less yellow during storage; however, their color was still pronounced. Activation energies and Q10 values for the yellowing of whey protein coatings were similar to those previously reported for the browning of whey powder. The results indicate that WPI coatings can be used in place of shellac coatings when low-color development is desired. WPC coatings can be used to tailor color development of a food. [ABSTRACT FROM AUTHOR]

Interactions of vanillin with soy, casein, and whey proteins were studied in aqueous model systems using a thermodynamic approach. Vanillin-protein binding was examined at 12 and 4 °C using 3 proteins and 6 vanillin concentrations. The results were analyzed using a Klotz plot. Number of binding sites (n) and dissociation constants (Kd) were derived from the plots. The thermodynamic parameters (ΔGº, ΔHº, and ΔSº) for the bindings were calculated. Under identical experimental conditions, whey protein was found to have higher affinity to vanillin than the other 2 proteins. Bindings of vanillin with casein and whey protein were enthalpy driven, while the interaction of vanillin with soy protein was highly entropy driven. The results inferred that conformational changes of soy protein might be important in binding of vanillin. [ABSTRACT FROM AUTHOR]

The emulsifying properties of six commercial milk protein products were studied. The products were separated into one of two groups depending on whether they contained aggregated (micellar) casein or disordered protein (casein or whey protein). Disordered proteins had a greater emulsifying ability than aggregated proteins. Dispersion of aggregated protein in dissociating buffer improved the emulsifying ability. Comparison of emulsion properties in simple oil-in-water emulsions with those in a model coffee whitener formulation showed that the lower emulsifying ability of aggregated protein could be partially compensated by other ingredients. [ABSTRACT FROM AUTHOR]

Myofibrils, oxidized with FeCl3/H2O2 ascorbate, exhibited an increase in carbonyls and amines, SH→SS conversion, peptide scission, myosin polymerization, and a decrease in thermal stability and gel-formation ability. Amino-acid side chains of whey-protein isolates (WPI) and soy-protein isolates (SPI) were also modified during oxidation, hut the thermal stability of WPI or SPI was not significantly altered. Oxidation Increased elasticity of SPI gel but not that of WPI gel. Similarly, oxidation promoted interactions of myofibrils with SPI but not with WPI, resulting in > 30% increases in elasticity of the myofibril/SPI composite gel over its nonoxidized control. Hence, in processed meats where oxidation occurs, the presence of soy proteins may enhance the functionality of myofibrillar proteins. [ABSTRACT FROM AUTHOR]

The effects of whey protein hydrolysis on film water vapor permeability (WVP) and solubility at 3 plasticizer levels were studied. Little or no significant difference (p > 0.05) appeared for film WVP between unhydrolyzed whey protein isolate (WPI), 5.5% degree of hydrolysis (DH) WPI and 10% DH WPI films at comparable plasticizer contents. However, increase in glycerol (gly) content significantly increased film WVR Thus, reduction in WPI molecular weight (MW) through hydrolysis may be a better approach to improving film flexibility than addition of plasticizer. Both 5.5% and 10% DH WPI had significantly different (p ≤ 0.05) film solubility compared to unhydrolyzed WPI. Soluble Protein (SP) and total soluble matter (TSM) of hydrolyzed WPI films were much higher than for unhydrolyzed WPI films. [ABSTRACT FROM AUTHOR]

Nonfat dry milk (NEDM), sodium caseinate {SC), whey protein concentrate (WPC), and combinations of each were evaluated for abilities to reduce pink color development in cooked, ground, uncured turkey breast. Protein treatments were also evaluated in the presence of pink-color-generating ligands {nicotinamide, 1%, sodium nitrite, 10 ppm, and sodium nitrate, 50 ppm) with and without ethylenedinitrilo-tetraacetic acid disodium salt (200 ppm). NFDM and WPC at levels as low as 1.5% were effective in reducing CIE a* values (P < 0.05) regardless of ligand treatment; SC was not. EDTA reduced pink color within all protein and ligand treatments. Poultry producers can reduce pink color development in further-processed products by selective addition of dairy proteins. [ABSTRACT FROM AUTHOR]

Dairy proteins were evaluated for their ability to reduce pink color in ground turkey samples. Sodium nitrite and nicotinamide were added to induce pink color formation. Nonfat dry milk (NFDM) and 1 of the whey protein concentrates (WPC) reduced CIE a* values in samples containing 10 ppm sodium nitrite. All of the dairy proteins tested reduced CIE a* values in nicotinamide-treated samples. In samples prepared without nicotinamide or nitrite, only WPC reduced CIE a* values, while the other proteins tested had no effect or increased redness. NFDM or specific WPC proteins could be used to reduce the pink color defect and Increase yield. [ABSTRACT FROM AUTHOR]

Focuses on a study which determined the effect of chemical pretreatment, flow rate, and two-phase flow on improving the permeate flux of cottage cheese whey during microfiltration. Materials and methods; Results of the study; Discussion.

Presents information on a study which examined the influence of hydrogen-ion concentration, protein concentration, heating temperature, and time on heat-denatured whey protein solutions that could be used as cold-gelling ingredients. Methodology of the study; Results and discussion of the study; Conclusions.

Focuses on a study which determined if a small decrease in acidity could be used to form a weak gel from whey protein polymers. Materials and method; Results and discussion; Conclusion.

Presents information on a study which investigated the compressive properties of whey protein composite gels containing fractionated milkfat. Materials and methods of the study; Gel preparation; Results and discussion; Conclusions.

Investigates the effects of casein:whey (C:W) protein ratios on the heat-induced aggregation/denaturation of whey proteins in model systems. Heat denaturation of whey proteins; Effect of C:W ratios on particle sizes in heated solutions; Microstructure of colloidal particles and casein localization.

Presents a study which investigated the water vapor permeability of whey protein isolate-beeswax emulsion films as related to pH. Film preparation; Lipid particle size analysis; Water vapor permeability measurements; Emulsion viscosity.

Provides information on a study which compared the fermentative production of lactan from sweet cheese whey medium without additions to that using a synthetic medium counterpart that had been previously tested. Materials and methods; Conclusions of the study.

Provides information on a study which monitored the creaming stability and viscosity of oil-in-water emulsions stabilized by whey protein isolate as functions of dextran sulfate and electrolyte concentration. Materials and methods; Results and discussion; Conclusions.

Establishes a flavor profile of pasteurized blends of cottage cheese whey and grapefruit juice. Effects of pasteurization, storage, lactose hydrolysis, and vacuum stripping on sensory characteristics; Trained sensory panel's rating of grapefruit, sweetness, sourness, astringency, cheesiness and saltiness.

Reports on a study which compared four methods for hydration measurements of various powders whey derivatives for intercorrelations and links to the chemical composition of the powders. Levels of hydration capacities obtained; Methods used which correlated with protein and lactose powder content enabling differentiation between the hydration capacities of whey protein concentrates and electrodialyzed whey powder; Results of the study.