The Influence of Bleaching Agent and Temperature on Bleaching Efficacy and Volatile Components of Fluid Whey and Whey Retentate

Fluid whey or retentate are often bleached to remove residual annatto Cheddar cheese colorant, and this process causes off‐flavors in dried whey proteins. This study determined the impact of temperature and bleaching agent on bleaching efficacy and volatile components in fluid whey and fluid whey retentate. Freshly manufactured liquid whey (6.7% solids) or concentrated whey protein (retentate) (12% solids, 80% protein) were bleached using benzoyl peroxide (BP) at 100 mg/kg (w/w) or hydrogen peroxide (HP) at 250 mg/kg (w/w) at 5 °C for 16 h or 50 °CC for 1 h. Unbleached controls were subjected to a similar temperature profile. The experiment was replicated three times. Annatto destruction (bleaching efficacy) among treatments was compared, and volatile compounds were extracted and separated using solid phase microextraction gas chromatography mass spectrometry (SPME GC‐MS). Bleaching efficacy of BP was higher than HP (P < 0.05) for fluid whey at both 5 and 50 °C. HP bleaching efficacy was increased in retentate compared to liquid whey (P < 0.05). In whey retentate, there was no difference between bleaching with HP or BP at 50 or 5 °C (P > 0.05). Retentate bleached with HP at either temperature had higher relative abundances of pentanal, hexanal, heptanal, and octanal than BP bleached retentate (P < 0.05). Liquid wheys generally had lower concentrations of selected volatiles compared to retentates. These results suggest that the highest bleaching efficacy (within the parameters evaluated) in liquid whey is achieved using BP at 5 or 50 °C and at 50 °C with HP or BP in whey protein retentate.     

Buffer Capacity of Cheese Wheys

Titration and buffer capacity curves of Mozzarella, Cheddar and Cottage cheese-type wheys were studied at concentrations of 6–24% solids. Buffer maxima due to lactate and phosphate occurred at pH 3.2 – 4.0 and 5.6 – 7.0, respectively, and were dependent on the type and concentration of whey. Titration curves of all whey varieties intersected at pH 3.7. An equation was developed to define whey pH as a function of pH at dipping, concentration and level of HCI or NaOH (r = 0.99, p < 0.01). The pH of Mozzarella and Cheddar cheese-type whey decreased during concentration but the pH of Cottage cheese whey increased. This difference is explained by calcium-phosphate equilibria in whey.     

The Effect of Feed Solids Concentration and Inlet Temperature on the Flavor of Spray Dried Whey Protein Concentrate

Previous research has demonstrated that unit operations in whey protein manufacture promote off‐flavor production in whey protein. The objective of this study was to determine the effects of feed solids concentration in liquid retentate and spray drier inlet temperature on the flavor of dried whey protein concentrate (WPC). Cheddar cheese whey was manufactured, fat‐separated, pasteurized, bleached (250 ppm hydrogen peroxide), and ultrafiltered (UF) to obtain WPC80 retentate (25% solids, wt/wt). The liquid retentate was then diluted with deionized water to the following solids concentrations: 25%, 18%, and 10%. Each of the treatments was then spray dried at the following temperatures: 180 °C, 200 °C, and 220 °C. The experiment was replicated 3 times. Flavor of the WPC80 was evaluated by sensory and instrumental analyses. Particle size and surface free fat were also analyzed. Both main effects (solids concentration and inlet temperature) and interactions were investigated. WPC80 spray dried at 10% feed solids concentration had increased surface free fat, increased intensities of overall aroma, cabbage and cardboard flavors and increased concentrations of pentanal, hexanal, heptanal, decanal, (E)2‐decenal, DMTS, DMDS, and 2,4‐decadienal (P < 0.05) compared to WPC80 spray dried at 25% feed solids. Product spray dried at lower inlet temperature also had increased surface free fat and increased intensity of cardboard flavor and increased concentrations of pentanal, (Z)4‐heptenal, nonanal, decanal, 2,4‐nonadienal, 2,4‐decadienal, and 2‐ and 3‐methyl butanal (P < 0.05) compared to product spray dried at higher inlet temperature. Particle size was higher for powders from increased feed solids concentration and increased inlet temperature (P < 0.05). An increase in feed solids concentration in the liquid retentate and inlet temperature within the parameters evaluated decreased off‐flavor intensity in the resulting WPC80.     

Permeate Flux During Ultrafiltration of Whey: Influence of Milk Coagulant Used for Cheese Manufacture

A pilot-scale plate and frame UF system was used to fractionate Cheddar cheese whey and study the effects of different commercial milk coagulants on permeate flux. Coagulants used in this study were calf rennet, Mucor pusillus protease, and Mucor miebei protease. Whey UF performance studies were conducted at a commercial Cheddar cheese plant and at Cornell under controlled conditions. Ultrafiltration was done in a continuous mode and initial concentration factor was set at 2× to simulate the first stage of a multistage whey UF system.Permeate flux decline was rapid in the first 30 min of UF for all wheys studied. More important, the type of milk coagulant used in cheese making had a profound effect on permeate flux during whey UF. No differences in the gross composition of the various wheys were correlated with differences in permeate flux. The highest permeate flux was measured for UF of whey produced during manufacture of Cheddar cheese using coagulant derived from Mucor pusillus. Lowest permeate flux was measured for UF of whey produced during manufacture of Cheddar cheese using calf rennet. Whey from cheese manufactured using Mucor miebei coagulant had flux performance intermediate to Mucor pusillus and calf rennet. The impact of milk coagulants on whey UF process efficiency should be considered by cheese makers.     

The effect of starter culture and annatto on the flavor and functionality of whey protein concentrate

The flavor of whey protein can carry over into ingredient applications and negatively influence consumer acceptance. Understanding sources of flavors in whey protein is crucial to minimize flavor. The objective of this study was to evaluate the effect of annatto color and starter culture on the flavor and functionality of whey protein concentrate (WPC). Cheddar cheese whey with and without annatto (15 mL of annatto/454 kg of milk, annatto with 3% wt/vol norbixin content) was manufactured using a mesophilic lactic starter culture or by addition of lactic acid and rennet (rennet set). Pasteurized fat-separated whey was then ultrafiltered and spray dried into WPC. The experiment was replicated 4 times. Flavor of liquid wheys and WPC were evaluated by sensory and instrumental volatile analyses. In addition to flavor evaluations on WPC, color analysis (Hunter Lab and norbixin extraction) and functionality tests (solubility and heat stability) also were performed. Both main effects (annatto, starter) and interactions were investigated. No differences in sensory properties or functionality were observed among WPC. Lipid oxidation compounds were higher in WPC manufactured from whey with starter culture compared with WPC from rennet-set whey. The WPC with annatto had higher concentrations of p-xylene, diacetyl, pentanal, and decanal compared with WPC without annatto. Interactions were observed between starter and annatto for hexanal, suggesting that annatto may have an antioxidant effect when present in whey made with starter culture. Results suggest that annatto has a no effect on whey protein flavor, but that the starter culture has a large influence on the oxidative stability of whey.     

Use of acid whey protein concentrate as an ingredient in nonfat cup set-style yogurt

Acid whey resulting from the production of soft cheeses is a disposal problem for the dairy industry. Few uses have been found for acid whey because of its high ash content, low pH, and high organic acid content. The objective of this study was to explore the potential of recovery of whey protein from cottage cheese acid whey for use in yogurt. Cottage cheese acid whey and Cheddar cheese whey were produced from standard cottage cheese and Cheddar cheese-making procedures, respectively. The whey was separated and pasteurized by high temperature, short time pasteurization and stored at 4°C. Food-grade ammonium hydroxide was used to neutralize the acid whey to a pH of 6.4. The whey was heated to 50°C and concentrated using ultrafiltration and diafiltration with 11 polyethersulfone cartridge membrane filters (10,000-kDa cutoff) to 25% total solids and 80% protein. Skim milk was concentrated to 6% total protein. Nonfat, unflavored set-style yogurts (6.0 ± 0.1% protein, 15 ± 1.0% solids) were made from skim milk with added acid whey protein concentrate, skim milk with added sweet whey protein concentrate, or skim milk concentrate. Yogurt mixes were standardized to lactose and fat of 6.50% and 0.10%, respectively. Yogurt was fermented at 43°C to pH 4.6 and stored at 4°C. The experiment was replicated in triplicate. Titratable acidity, pH, whey separation, color, and gel strength were measured weekly in yogurts through 8 wk. Trained panel profiling was conducted on 0, 14, 28, and 56 d. Fat-free yogurts produced with added neutralized fresh liquid acid whey protein concentrate had flavor attributes similar those with added fresh liquid sweet whey protein but had lower gel strength attributes, which translated to differences in trained panel texture attributes and lower consumer liking scores for fat-free yogurt made with added acid whey protein ingredient. Difference in pH was the main contributor to texture differences, as higher pH in acid whey protein yogurts changed gel structure formation and water-holding capacity of the yogurt gel. In a second part of the study, the yogurt mix was reformulated to address texture differences. The reformulated yogurt mix at 2% milkfat and using a lower level of sweet and acid whey ingredient performed at parity with control yogurts in consumer sensory trials. Fresh liquid acid whey protein concentrates from cottage cheese manufacture can be used as a liquid protein ingredient source for manufacture of yogurt in the same factory.     

Evaluation of Yield and Quality of Cheddar Cheese Manufactured from Milk with Added Whey Protein Concentrate

Cheddar cheese was produced from whole milk with blends of whey protein concentrates added. Two whey protein concentrate powders containing 35 or 55% protein were each reconstituted to a 15% (wt/wt) suspension and heat treated at 70°C for 15 min. Addition of the denatured whey protein concentrate suspension to the milk was at 5 or 10% by weight of the milk. Addition of reconstituted partially denatured whey protein concentrate increased cheese yields from 1.4 to 6.2% above those of the control on a 63% solids basis. The only significant (P<.05) increase in yield was from the 55% whey protein concentrate suspension at 10% replacement by weight of the milk. The correlation coefficient between percent denaturation in the whey protein concentrate and yield in this cheese was .62. Experimental cheese had decreased fat and total solids contents and increased total nitrogen, ash, and salt. Fat reduction varied from 4.3 to 18.2% below the control cheese, and total solids were from 1.7 to 8.9% below the control cheeses. Total nitrogen values of experimental cheese were from .73 to 5.64% above the control. Cheeses were evaluated organoleptically; more flavor defects were associated with increased whey protein concentrate in the experimental cheese. The most common criticism of the experimental cheese was an atypical (unclean) cheese flavor.     

Hydroxyl Radical-Stressed Whey Protein Isolate: Chemical and Structural Properties

Many whey protein-containing foods are prepared in the presence of reactive oxygen species generated during processing. The objective of the present study was to determine chemical and structural changes, including carbonyls, sulfhydryls (SHs), dityrosine, surface hydrophobicity, turbidity, and cross-linking, in whey protein isolate (WPI) exposed to FeCl₃/H₂O₂ hydroxyl radical-generating systems (HRGS) at room temperature (20 °C). Protein carbonyl content in WPI increased (P < 0.05) with increasing concentrations of H₂O₂ when incubated for up to 10 h; total SH groups decreased (P < 0.05) in a similar fashion. The HRGS-oxidized WPI also showed a higher dityrosine content, surface hydrophobicity, and turbidity (P < 0.05) than nonoxidized WPI. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed substantial losses of β-lactoglobulin, α-lactalbumin, and bovine serum albumin, and a concomitant formation of protein polymers in oxidized WPI. The protein-oxidation indexes were all significantly correlated (P < 0.01). These oxidation-induced changes demonstrate high susceptibility of WPI to oxidative stress at room temperature and may explain variations in functionality of whey proteins often observed in formulated foods.     

Electrophoretic studies of chhana whey and effect of temperature and time of storage on its quality

Chhana whey contains less protein than Cheddar cheese whey, acid casein and cottage cheese whey, and the protein composition is quite different. Electrophoretic methods demonstrated that most of the proteins in chhana whey were denatured, and there was considerable variation in the protein composition between samples of chhana whey and paneer whey obtained from different sources. The effect of storage temperature and time (up to 10 h at 40°C, 50°C, 60°C, 70°C and 80°C) on the quality of chhana whey was investigated. There were no significant changes in the pH and titratable acidity in any of these cases. Electrophoretic separation showed no qualitative changes in the protein composition pattern of chhana whey after up to 10 h of storage at 70°C.     

Viscoelastic properties of caseinmacropeptide isolated from cow,ewe and goat cheese whey

Caseinmacropeptide (CMP) is a C‐terminal glycopeptide released from κ‐casein by the action of chymosin during cheese‐making. It is recognised as a bioactive peptide and is thought to be an ingredient with a potential use in functional foods. CMP occurs in sweet cheese whey and whey protein concentrate (WPC). Its composition is variable and depends on the particular whey source and the fractionation technology employed in the isolation. There were no significant (P < 0.05) differences in the relative apparent viscosities between species of CMPs (cow, ewe and goat). Analyses at different pH (2, 4, 7, 10), ionic strength (0, 0.2, 0.4 and 0.7 as NaCl molarity) and protein concentration (50, 100 and 200 g kg^?1) at temperatures from 10 to 90 °C carried out found pH 7 and high protein concentration (200 g kg^?1) conditions to be the best for CMP solutions to keep low and constant relative viscosity values with increasing temperature up to 75 °C. The viscoelastic properties–storage modulus, loss modulus and phase angle–of the different CMPs and WPC solutions were determined. Heat‐induced rheological changes in CMP solutions occurred at moderate temperatures (40–50 °C) with no appreciable differences in viscosity. Gelation took place significantly (P < 0.05) earlier in goat CMP (41 °C), followed by cow CMP (44 °C), ewe CMP (47 °C) and WPC (56 °C). Heating at 90 °C showed that WPC required significantly (P < 0.05) longer times to form gels (>5 min) than the CMPs (<5 min). WPC gels had higher (>20°) phase angle than CMP (<20°), which could be associated with untidy structures, limiting elastic properties of the gel. Copyright © 2006 Society of Chemical Industry     

Effect of minor milk proteins in chymosin separated whey and casein fractions on cheese yield as determined by proteomics and multivariate data analysis

The objective of this work was to find regressions between minor milk proteins or protein fragments in the casein or sweet whey fraction and cheese yield because the effect of major milk proteins was evaluated in a previous study. Proteomic methods involving 2-dimensional gel electrophoresis and mass spectrometry in combination with multivariate data analysis were used to study the effect of variations in milk protein composition in chymosin separated whey and casein fractions on cheese yield. By mass spectrometry, a range of proteins significant for the cheese yield was identified. Among others, a C-terminal fragment of β-casein had a positive effect on the cheese yield expressed as grams of cheese per 100 g of milk, whereas several other minor fragments of β-, α_s1-, and α_s2-casein had positive effects on the transfer of protein from milk to cheese. However, the individual effect of each identified protein was relatively low. Therefore, further studies of the relations between different proteins/peptides in the rennet casein or sweet whey fractions and cheese yield are needed for advanced understanding and prediction of cheese yield.     

乳清在Mozzarella干酪加工中的应用初探

通过在Mozzarella干酪加工中添加一定量的乳清形成产品,并对是否添加乳清的Mozzarella干酪进行不同成熟时间的感官、质构、融化性、油脂析出性和色差等指标的比较,对产品在不同成熟时间所表现出的主要理化特性和功能特性进行分析研究,初步探讨了添加乳清对Mozzarella干酪品质的影响。