Survey of salty and sweet whey composition from various cheese plants in Wisconsin

Salty whey is currently underutilized in the dairy industry because of its high salt content and increased processing and disposal costs. Salty whey accounts for 2 to 5% of the total whey generated during Cheddar and other dry-salted cheese manufacture. Because relatively little information is available on salty whey, this study was conducted to determine the range of compositional components in salty whey from commercial cheese plants. Gross compositional differences in percent protein, salt, solids, and fat between sweet whey and salty whey from various dry-salted cheeses from 8 commercial plants were determined. Differences between individual whey protein compositions were determined using sodium dodecyl sulfate-PAGE. Average total solids, fat, and salt content were significantly greater in the salty whey compared with the corresponding sweet whey. True protein was reduced in salty whey although great variability existed among samples. Individual whey proteins identified included lactoferrin (Lf), BSA, immunoglobulin G, β-lactoglobulin, and α-lactalbumin. Salty whey showed an increase in Lf content and a decrease in α-lactalbumin and β-lactoglobulin content when compared with sweet whey. Salty whey may be a source of Lf, potentially increasing its value to whey processors. However, the compositional assessments showed that commercial salty whey is a highly variable waste stream.     

Milk clotting and proteolytic activity of an enzyme preparation from Bromelia hieronymi fruits

A new enzyme preparation (hieronymain), obtained from unripe fruits of Bromelia hieronymi Mez (Bromeliaceae), was assayed for its ability to clot milk and hydrolyze bovine casein and milk whey proteins. Caseinolytic activity at 30 °C and pH 6.5 (milk clotting conditions) was 3.3 Ucas/mL and milk clotting activity was 40 ± 0.2 IMCU/mL. The κ-casein fraction, involved in the clotting formation, began to be degraded after 10 min of reaction, while the degradation of the other casein fractions proceeded slowly enough as to guarantee the production of a firm curd, with no evidence of extensive hydrolysis, a necessary condition for cheese making. In the case of whey proteins, bovine serum albumin and α-lactalbumin were quickly degraded after 30 min, while β-lactoglobulin was considerably degraded only after 60 min at 50 °C. Miniature cheeses were manufactured both with chymosine and hieronymain and analyzed by a taste panel, who found acceptable both cheeses. Hieronymain might be appropriate for cheese making, as well as for the production of milk protein hydrolysates.     

A microfiltration process to maximize removal of serum proteins from skim milk before cheese making

Microfiltration (MF) is a membrane process that can separate casein micelles from milk serum proteins (SP), mainly beta-lactoglobulin and alpha-lactalbumin. Our objective was to develop a multistage MF process to remove a high percentage of SP from skim milk while producing a low concentration factor retentate from microfiltration (RMF) with concentrations of soluble minerals, nonprotein nitrogen (NPN), and lactose similar to the original skim milk. The RMF could be blended with cream to standardize milk for traditional Cheddar cheese making. Permeate from ultrafiltration (PUF) obtained from the ultrafiltration (UF) of permeate from MF (PMF) of skim milk was successfully used as a diafiltrant to remove SP from skim milk before cheese making, while maintaining the concentration of lactose, NPN, and nonmicellar calcium. About 95% of the SP originally in skim milk was removed by combining one 3 x MF stage and two 3 x PUF diafiltration stages. The final 3 x RMF can be diluted with PUF to the desired concentration of casein for traditional cheese making. The PMF from the skim milk was concentrated in a UF system to yield an SP concentrate with protein content similar to a whey protein concentrate, but without residuals from cheese making (i.e., rennet, culture, color, and lactic acid) that can produce undesirable functional and sensory characteristics in whey products. Additional processing steps to this 3-stage MF process for SP removal are discussed to produce an MF skim retentate for a continuous cottage cheese manufacturing process.     

Changes in the soluble nitrogen fraction of milk throughout PDO Grana Padano cheese-making

The behaviour of soluble nitrogen compounds during Grana Padano cheese-making was studied at eight dairies. Raw milk, skimmed milk, sweet whey and the derived natural whey culture, collected from 24 processes, were analysed for soluble whey proteins (α-lactalbumin and β-lactoglobulin), proteose-peptones (PP), small peptides (SP), caseinomacropeptides (CMPs), and free amino acids (FAAs). The PP fraction increased during milk natural creaming, then part of it was selectively retained in the curd and the rest degraded in the first few hours of whey fermentation, together with α-lactalbumin, CMPs and part of SP. Features outlined for the whey culture were confirmed on 30 samples collected at six different dairies. A time course study of the whey fermentation showed that degradation of α-lactalbumin began when the pH dropped below 4, whereas β-lactoglobulin content did not change. Uptake of specific FAAs was shown to support the initial growth of lactic acid bacteria in whey.     

Effects of In Vitro Proteolysis on the Allergenicity of Major Whey Proteins

The effects of in vitro proteolysis on the allergenicity of major whey proteins (α-lactalbumin and β-lactoglobulin) by simulating the human gastrointestinal conditions were evaluated. The proteolysis of demineralized whey with pepsin (pH 2.0 for 30 min) and/or various pancreatic enzymes (pH 7.5 for 60 and 240 min) was performed by the pH-stat technique at 37°C. The enzyme inactivation was performed by heating at 80°C for 20 min. Allergenicity of the hydrolyzates was evaluated by RAST inhibition using sera obtained from children allergic to whey proteins. Selective proteolysis of whey by pepsin and α-chymotrypsin was the most efficient combination of enzymes to reduce the allergenicity of both α-lactalbumin and β-lactoglobulin. The above hydrolyzate could be used to develop an ingredient for infant milk formula with a lower allergenicity.     

超滤技术在干酪生产中的应用

对超滤技术在干酪生产中的应用作以综述.原料乳通过超滤,脂肪、细菌、酪蛋白和乳清蛋白等大分子颗粒被浓缩,其成分及缓冲能力等的变化对干酪加工成熟过程均产生了重要的影响.超滤技术应用于乳清可以生产乳糖、乳清粉、乳清蛋白浓缩物、乳清蛋白分离物甚至β-乳球蛋白、α-乳白蛋白、糖巨肽及乳铁蛋白等高附加值的产品.     

Introduction of High Pressure to Food Processing: Preferential Proteolysis of β-Lactoglobulin in Milk Whey

Various proteins were subjected to thermolysin digestion at 2000 atm. Casein and soy protein were extensively digested at both atmospheric and high pressures, but the tetrameric proteins alcohol dehydrogenase and hemoglobin and the monomeric protein β-lactoglobulin were degraded only upon pressurization. Globular proteins with many disulfide bonds (RNase A, lysozyme, and α-lactalbumin) resisted the proteolysis at both pressures. These observations led to the preferential digestion of β-lactoglobulin in cow's milk whey, thus simulating human milk protein. The versatility of pressure-induced proteolysis in food processing is also proposed.     

Selective separation of the major whey proteins using ion exchange membranes

Synthetic microporous membranes with functional groups covalently attached were used to selectively separate β-lactoglobulin, BSA, and α-lactalbumin from rennet whey. The selectivity and membrane performance of strong (quaternary ammonium) and weak (diethylamine) ion-exchange membranes were studied using breakthrough curves, measurement of binding capacity, and protein composition of the elution fraction to determine the binding behavior of each membrane. When the weak and strong anion exchange membranes were saturated with whey, they were both selective primarily for β-lactoglobulin with less than 1% of the eluate consisting of α-lactalbumin or BSA. The binding capacity of a pure β-lactoglobulin solution was in excess of 1.5 mg/cm² of membrane. This binding capacity was reduced to approximately 1.2 mg/cm² when using a rennet whey solution (pH 6.4). This reduction in protein binding capacity can be explained by both the competitive effects of other whey proteins and the effect of ions present in whey. Using binary solution breakthrough curves and rennet whey breakthrough curves, it was shown that α-lactalbumin and BSA were displaced from the strong and weak anion exchange membranes by β-lactoglobulin. Finally, the effect of ionic strength on the binding capacity of individual proteins for each membrane was determined by comparing model protein solutions in milk permeate (pH 6.4) and a 10 mM sodium phosphate buffer (pH 6.4). Binding capacities of β-lactoglobulin, α-lactalbumin, and BSA in milk permeate were reduced by as much as 50%. This reduction in capacity coupled with the low binding capacity of current ion exchange membranes are 2 serious considerations for selectively separating complex and concentrated protein solutions.     

Degradation of α-Lactalbumin and β-Lactoglobulin by Actinidin

Susceptibility of the two major whey proteins, β-lactoglobulin and α-lactalbumin, to enzymatic degradation by actinidin as a function of pH and temperature was examined by a response surface methodology in order to elucidate the enzymatic action of the protease for controlled modification of these whey proteins. Pure whey protein fractions and commercial spray-dried whey were degraded by actinidin. The simultaneous effects of pH and temperature, in a range of 2.3 to 5 and 41 to 58°C respectively, on whey proteins degradation were studied, demonstrating a clear interrelationship between these two variables. With commercial whey, extended proteolysis of both β-lactoglobulin and α-lactalbumin was observed at pH 4.0 and temperature of 41.6°C; after an incubation time of 120 min, a degradation of 43.6% was obtained for the former, and 89.1% for the latter. Assays on pure proteins showed a complete degradation of α-lactalbumin and a 65.3% of degradation for β-lactoglobulin; therefore, the former appeared to be more susceptible to actinidin proteolysis.     

Effect of a food-grade enzyme preparation fromAspergillus oryzae on free fatty acid release in Manchego-type cheese from ovine and bovine milk

The addition of 50 mg Flavor Age (blend of lipase, proteinases and peptidases fromAspergillus oryzae) per kilogram of mixed ovine plus bovine milk for the manufacture of Manchego-type cheese caused the release of abundant free fatty acids (FFA), especially the short-chain fatty acids (C₄ to C₁₀). The effect accentuated with ripening time, the cheeses reaching a level of FFA around 2% at 120 days. The high concentration of FFA could have partially inhibited the growth of starter culture, as can be deduced from the higher residual lactose content of enzyme-treated cheeses. The results are compared and related to those obtained in a previous study on proteolysis and flavour development by the same enzyme preparation. They suggest that in the case of Man-chego-type cheese the liberation of FFA, although necessary, could be less important for flavour enhancement than the production of free amino acids.     

Effect of somatic cell count on Prato cheese composition

The objective of this research was to evaluate the effect of 2 levels of somatic cell counts (SCC) in raw milk on Prato cheese composition, protein and fat recovery, cheese yield, and ripening. A 2 × 6 factorial design with 3 replications was performed in this study: 2 levels of SCC and 6 levels of storage time. Initially, 2 groups of dairy cows were selected to obtain low (<200,000 cells/ mL) and high (>600,000 cells/mL) SCC in milks that were used to manufacture 2 vats of cheese: 1) low SCC and 2) high SCC. Milk, whey, and cheese compositions were evaluated; clotting time was measured; and cheese yield, protein recovery, and fat recovery were calculated. The cheeses were evaluated after 5, 12, 19, 26, 33, and 40 d of ripening according to pH, moisture, pH 4.6 soluble nitrogen, 12% trichloroacetic acid soluble nitrogen as a percentage of total nitrogen, and firmness. High-SCC milk presented significantly higher total protein and nonprotein nitrogen and lower true protein and casein concentrations than did low-SCC milk, indicating an increased whey protein content and a higher level of proteolysis. Although the pH of the milk was not affected by the somatic cell level, the cheese obtained from high-SCC milk presented significantly higher pH values during manufacture and a higher clotting time. No significant differences in cheese yield and protein recovery were observed for these levels of milk somatic cells. The cheese from high-SCC milk was higher in moisture and had a higher level of proteolysis during ripening, which could compromise the typical sensory quality of the product.     

Effect of milk centrifugation and incorporation of high-heat-treated centrifugate on the composition,texture, and ripening characteristics of Maasdam cheese

This study investigated the effect of centrifugation (9,000 × g, 50°C, flow rate = 1,000 L/h), as well as the incorporation of high-heat-treated (HHT) centrifugate into cheese milk on the composition, texture, and ripening characteristics of Maasdam cheese. Neither centrifugation nor incorporation of HHT centrifugate into cheese milk had a pronounced effect on the compositional parameters of any experimental cheeses, except for moisture and moisture in nonfat substance (MNFS) levels. Incorporation of HHT centrifugate at a rate of 6 to 10% of the total milk weight into centrifuged milk increased the level of denatured whey protein in the cheese milk and also increased the level of MNFS in the resultant cheese compared with cheeses made from centrifuged milk and control cheeses; moreover, cheese made from centrifuged milk had ～3% higher moisture content on average than control cheeses. Centrifugation of cheese milk reduced the somatic cell count by ～95% relative to the somatic cell count in raw milk. Neither centrifugation nor incorporation of HHT centrifugate into cheese milk had a significant effect on age-related changes in pH, lactate content, and levels of primary and secondary proteolysis. However, the value for hardness was significantly lower for cheeses made from milk containing HHT centrifugate than for other experimental cheese types. Overall, centrifugation appeared to have little effect on composition, texture, and ripening characteristics of Maasdam cheese. However, care should be taken when incorporating HHT centrifugate into cheese milk, because such practices can influence the level of moisture, MNFS, and texture (particularly hardness) of resultant cheeses. Such differences may have the potential to influence subsequent eye development characteristic, although no definitive trends were observed in the present study and further research on this is recommended.     

The effect of adding whey protein particles as inert filler on thermophysical properties of fat‐reduced semihard cheese type Gouda

The effect of added microparticulated whey protein (Simplesse^®) on textural and thermophysical properties of fat‐reduced semihard cheese type Gouda was investigated. Full‐fat, reduced‐fat and low‐fat cheeses were manufactured of comparable moisture content, each made of control milk and milk systems containing 1% Simplesse^®, respectively. Whey protein particles improved textural properties of reduced‐fat and low‐fat cheese. Meltability and flowability were significantly enhanced by an increased fat level, Simplesse^® addition and ripening time. The results emphasise the role of microparticulated whey proteins acting as an inert filler within the composite cheese matrix and allow textural and thermophysical properties of fat‐reduced cheeses to be adjusted towards cheese with higher fat content.     

Production and partial purification of proteases from Aspergillus oryzae grown in a medium based on whey protein as an exclusive nitrogen source

Several attempts have been made to incorporate whey proteins into curd to increase cheese yield. For some types of cheese, degradation of whey proteins that have been incorporated into the curd would be required to obtain acceptable flavor and texture. On the basis of the high potential for protease synthesis in Aspergillus oryzae, sodium nitrate as a nitrogen source in a minimal medium for fungi, known as Czapek-Dox medium, was replaced with whey protein isolate to induce the protease to hydrolyze whey protein using A. oryzae AHU7146. A solid-phase medium adjusted to pH 6 was suitable for this purpose when incubation was carried out at 25°C for 2 wk. The application of column chromatography enabled the resolution of 3 proteolytic components (1, 2, and 3). With respect to optimal temperature and zymographic analysis, component 1 was similar to component 3. In contrast, component 2 was less abundant than the other components and exhibited activity in the alkaline pH region. The degradation of β-lactoglobulin and α-lactalbumin in whey protein isolate solution by the crude enzyme was primarily attributed to the action of components 1 and 3, based on HPLC analysis and the N-terminal amino acid sequences; however, zymography demonstrated evident proteolysis due to component 2. Because heat-denatured whey protein aggregates were digestible by the crude enzyme, the proteolytic system from A. oryzae has the potential as an additive to stimulate the ripening of cheese enriched with whey protein.     

The effect of heat treatment of caprine milk on the composition of cheese whey

In three independent trials, caprine milk from the same batch was divided into three lots, which were heated at 65 °C for 30 min, 80 °C for 5 min or 90 °C for 5 min. Representative whey samples collected during the whole cheese making process were analysed for fat, protein and dry matter contents, which decreased as the heating temperature of milk increased. Percentages of serum albumin and β-lactoglobulin in the total proteins of whey decreased as the heating temperature of milk increased, while α-lactalbumin and glycomacropeptide increased, particularly in the 90 °C whey. Lactoferrin and the immunoglobulin-heavy chain were only detected in the 65 °C whey.     

Application of proteomic techniques to protein and peptide profiling of Teleme cheese made from different types of milk

Water-soluble extracts of Teleme cheeses prepared from sheep, goat or cow milk and matured 120 days have been analysed for constituent peptides and proteins using proteomics. Techniques used include: (a) two-dimensional gel electrophoresis, with matrix-assisted laser desorption ionisation/mass spectrometry, (b) high-performance liquid chromatography in conjunction with mass spectrometry and Edman degradation and (c) tandem mass spectrometry. Gel electrophoresis showed species-specific differences in whey proteins and peptides from caseins but differences could not be resolved unambiguously using available databases. From high-performance liquid chromatography individual peaks were shown to be composed of a spectrum of peptides, with -lactalbumin, β-lactoglobulin and a spectrum of casein-derived peptides most abundant. Tandem mass spectrometry detected casein-derived peptides with mass range 3000–1500 Da and identified species-specific differences. Overall, the peptide profile for Teleme cheese is typical of other cheeses and the species milk source can be resolved through proteomics.     

Effect of β-lactoglobulin A and B whey protein variants on cheese yield potential of a model milk system

Cheese yield mainly depends on the amount and proportion of milk constituents; however, genetic variants of the proteins present in milk may also have an important effect. The objective of this research was to study the effect of the variants A and B of β-lactoglobulin (LG) on cheese yield using a model system consisting of skim milk powder fortified with different levels of a mixture containing α-lactalbumin and β-LG genetic variants (A, B, or A-B) in a 1:2 ratio. Fortified milk samples were subjected to pasteurization at 65°C for 30 min. Miniature cheeses were made by acidifying (pH = 5.9) fortified milk and incubating with rennet for 1 h at 32°C. The clot formed was cut, centrifuged at 2,600 × g for 30 min at 20°C and drained for determining cheese yield. Cheese-yielding capacity was expressed as actual yield (grams of cheese curd per 100 g of milk) and dry weight yield (grams of dried cheese curd per 100 g of milk). Free-zone capillary electrophoresis was used for determining β-LG A or B recovery in the curd during rennet-induced coagulation. The presence of β-LG variant B resulted in a significantly higher actual and dried weight cheese yield than when A or A-B were present at levels ≤0.675% of whey protein (WP) addition. Results of free-zone capillary electrophoresis allowed us to infer that β-LG B associates with the casein micelles during renneting, as shown by an increase in the recovery of this variant in the curd when β-LG B was added up to a maximum at 0.45% (equivalent to 0.675% WP). In general, actual or dried weight cheese yield increased as WP addition was increased from 0.225 to 0.675%. However, when WP addition ranged from 0.675 to 0.90%, a drastic drop in cheese yield was observed. This behavior may be because an increase in the aggregation of casein micelles with a concomitant inclusion of whey protein in the gel occurs at low levels of WP addition, whereas once the association of WP with the casein micelles reach a saturation point at addition levels higher than 0.675%, rearrangements of the gel network result in larger whey expulsion and syneresis. This knowledge is expected to be useful to maximize cheese yield and optimize processing conditions during cheese and cheese analogs manufacturing.     

Use of chitosan for selective removal of beta-lactoglobulin from whey

A method is described for selective removal of undenatured β-lactoglobulin from cheese whey based on interactions between whey proteins and chitosan. Whey was previously clarified at pH 4.5 with addition of chitosan (25 mg/100 mL), and selective removal of β-lactoglobulin was studied in the pH interval 4.6 to 6.5. Addition of chitosan caused selective precipitation of β-lactoglobulin that increased with pH. The content of β-lactoglobulin in whey decreased as the amount of chitosan added was increased. At pH 6.2, addition of 1.9 to 3.0 mg/mL of chitosan led to complete removal of β-lactoglobulin, whereas at least 80% of the rest of whey proteins remained in solution. The production of cheese whey without β-lactoglobulin could help to expand the applications of dairy by-products in food processing, and to isolate hypoallergenic whey protein concentrates.     

Milk species identification in cheese varieties using electrophoretic,chromatographic and PCR techniques

Different methods were applied to standard mixtures of milk from different species and to model cheeses of different ages to study their applicability for the detection of cows’ milk and determination of the percentage of cows’ milk in mixed milk cheeses. Urea–polyacrylamide gel electrophoresis (urea–PAGE) and anion-exchange high performance liquid chromatography (HPLC) of caseins was restricted to the control of the adulteration of milk. Isoelectric focusing (IEF) of γ-caseins according the EU reference method was well suited for detection of cows’ milk even in matured cheese, but could not discriminate ewes’ milk from goats’ milk. IEF and cation-exchange HPLC of para-κ-caseins were appropriate for differentiation of bovine, ovine and caprine milk. Urea–PAGE and IEF of whey proteins was useful for the species authentication of whey cheeses. Polymerase chain reaction using species–specific primers was a highly sensitive technique for the qualitative detection of cows’ milk even in overripe mixed cheese.     

Application of a membrane technology to remove bacteriophages from whey

Whey from former cheese batches can be recycled either to increase the yield or to improve texture properties of fat reduced cheeses. However, in the case of the presence of bacteriophages, pasteurization may not be sufficient to eliminate phages in whey. Therefore, in this work, a cross-flow membrane filtration process was designed to separate whey proteins from whey-derived phages. Filtration experiments were carried out using native whey as model filtration medium, three polyethersulfone membranes (100, 300 and 500 kDa) that were studied in detail, and lactococcal phage P008. Filtration performance was characterized by phage retention, total whey protein permeation, and permeation of the major whey proteins α-lactalbumin and β-lactoglobulin. Filtration experiments showed that it is possible to reduce the number of phages in whey by filtration to a level at which subsequent phage multiplication is minimized and, concomitantly, high protein permeation through the membrane is ensured.