Effects of protein and fat levels in milk on cheese and whey compositions

Bulk tank milk was standardised to six levels of fat (3·0, 3·2, 3·4, 3·6, 3·8, 4·0%) and similarly to six levels of protein, thus giving a total of 36 combinations in composition. Milk was analyzed for total solids, fat, protein, casein, lactose and somatic cell count and was used to make laboratory-scale cheese. Cheese samples from each batch were assayed for total solids, fat, protein and salt. Losses of milk components in the whey were also determined. Least squares analysis of data indicated that higher protein level in milk was associated with higher protein and lower fat contents in cheese. This was accompanied by lower total solids (higher moisture) in cheese. Inversely, higher fat level in milk gave higher fat and lower protein and moisture contents in cheese. Higher fat level in milk resulted in lower retention of fat in cheese and more fat losses in the whey. Higher protein level in milk gave higher fat retention in cheese and less fat losses in the whey. Regression analysis showed that cheese fat increased by 4·22%, while cheese protein decreased by 2·61% for every percentage increase in milk fat. Cheese protein increased by 2·35%, while cheese fat decreased by 6·14% per percentage increase in milk protein. Milk with protein to fat ratio close to 0·9 would produce a minimum of 50% fat in the dry matter of cheese.     

Effect of denatured whey protein concentrate and its fractions on cheese composition and rheological properties

The objectives of this study were (1) to assess the effect of a denatured whey protein concentrate (DWPC) and its fractions on cheese yield, composition, and rheological properties, and (2) to separate the direct effect of the DWPC or its fractions on cheese rheological properties from the effect of a concomitant increase in cheese moisture. Semihard cheeses were produced at a laboratory scale, and mechanical properties were characterized by dynamic rheometry. Centrifugation was used to induce a moisture gradient in cheese to separate the direct contribution of the DWPC from the contribution of moisture to cheese mechanical properties. Cheese yield increased and complex modulus (G*) decreased when the DWPC was substituted for milk proteins in milk. For cheeses with the same moisture content, the substitution of denatured whey proteins for milk proteins had no direct effect on rheological parameters. The DWPC was fractionated to evaluate the contribution of its different components (sedimentable aggregates, soluble component, and diffusible component) to cheese yield, composition, and rheological properties. The sedimentable aggregates were primarily responsible for the increase in cheese yield when DWPC was added. Overall, moisture content explained to a large extent the variation in cheese rheological properties depending on the DWPC fraction. However, when the effect of moisture was removed, the addition of the DWPC sedimentable fraction to milk increased cheese complex modulus. Whey protein aggregates were hypothesized to act as active fillers that physically interact with the casein matrix and confer rigidity after pressing.     

Production of low antigenic cheese whey protein hydrolysates using mixed proteolytic enzymes

This study examined the effect of different proteolytic enzymes on the production of cheese whey protein (CWP) hydrolysates with low antigenicity. Four enzyme combinations (1:1) trypsin + papain W‐40 (TP), trypsin + neutrase 1.5 (TN), papain W‐40 + protease S (PP) and papain W‐40 + neutrase 1.5 (PN) were added at the rate of 1% of the CWP and it was incubated for 15, 30, 60, 90, 120 and 180 min at 50 °C. CWP hydrolysis and its non‐protein nitrogen concentrations were higher with TP and TN compared with PP and PN at all incubation times. The SDS‐PAGE revealed complete removal of α‐lactalbumin (α‐LA) and β‐lactoglobulin (β‐LG) from hydrolysates produced by trypsin‐containing enzyme mixtures. Reverse‐phase HPLC analysis ascertained the CWP hydrolysis and SDS‐PAGE results. The lowest antigenicity in CWP hydrolysates was observed with the use of trypsin‐containing enzyme mixtures compared with other enzyme combinations. Present results suggested that TP and TN combinations were the most effective for CWP hydrolysis for the removal of β‐LG from CWP. Further research is warranted to identify the peptides in CWP hydrolysates produced with these enzyme combinations that may help enhance the utilisation of whey protein in human food. Copyright © 2007 Society of Chemical Industry     

原料乳中蛋白质与脂肪比例对 Mozzarella干酪品质的影响

采用3×3拉丁方试验设计,3个奶酪槽中原料乳的蛋白质与脂肪质量比分别为1∶1,1.2∶1,1.3∶1(通过添加脱脂干奶粉调整蛋白质含量)。研究蛋白质与脂肪比例对Mozzarella干酪的品质的影响。结果表明,随着原料乳中蛋白质脂肪比例的增加,干酪的含水量、油脂析出性显著降低(P<0.05),干酪的弹性显著升高(P<0.05),蛋白质与脂肪比例对Mozzarella干酪的蛋白质水解没有显著的影响。     

Use of chitosan to prolong mozzarella cheese shelf life

This study was undertaken to evaluate the feasibility of using chitosan, a natural antimicrobial substance, to improve the preservation of a very perishable cheese. The effectiveness of chitosan to inhibit the growth of spoilage microorganisms in Mozzarella cheese was studied during refrigerated storage. A lactic acid/chitosan solution was added directly to the starter used for Mozzarella cheese manufacturing. Mozzarella cheese samples were stored at 4°C for about 10 d and microbial populations as well as the pH were monitored. Results demonstrated that chitosan inhibited the growth of some spoilage microorganisms such as coliforms, whereas it did not influence the growth of other microorganisms, such as Micrococcaceae, and lightly stimulated lactic acid bacteria.     

Effect of electron beam irradiation on the shelf life of mozzarella cheese

The effectiveness of electron beam irradiation on the shelf life of mozzarella cheese was evaluated using five different irradiation doses and a control cheese. Shelf life tests were run at 10 °C by determining the cell load of spoilage micro‐organisms monitored on the consecutive days during storage. By fitting the experimental data through a modified version of the Gompertz equation, the shelf life of samples irradiated to the different doses was calculated. Results show significant increases in the shelf life of the investigated cheese. There were slight differences in the functional properties such as stretching, oiling off, melting between irradiated and unirradiated cheeses at 260 °C in oven. Our results indicated that the electron irradiation at the dose of 2.0 kGy may inhibit the growth of spoilage micro‐organisms such as coliforms and Pseudomonas sp. without affecting the sensorial characteristics of the product.     

Chitosan/whey protein film as active coating to extend Ricotta cheese shelf-life

Shelf-life extension of Ricotta cheese coated with a chitosan/whey protein edible film and stored under modified atmosphere at 4 °C was evaluated. The chitosan/whey protein film had 35% and 21% lower oxygen and carbon dioxide permeability, respectively, and about three times higher water vapor permeability than film prepared with chitosan alone. Over a 30-day storage period, no differences in the pH of control and coated Ricotta cheeses were observed. While the titratable acidity of the control increased linearly during the first two weeks and remained constant for the rest of the storage period, the corresponding values for coated Ricotta cheese did not change significantly during the first 21 days and reached the acidity level (0.34 ± 0.02 milliequivalent/100 g of analyzed sample) of the control only on day 30. The viable numbers of lactic acid bacteria and mesophilic and psychrotrophic microorganisms were significantly lower (p < 0.05) in the chitosan/whey protein coated cheese, compared to the control, at each storage time. Our findings suggest a potential utility of chitosan/whey protein coatings to extend fresh dairy product shelf-life.     

Water buffalo mozzarella cheese stored in polysaccharide-based gels: correlation between prolongation of the shelf-life and physicochemical parameters

An innovative packaging system has been developed, based on natural gels, that has shown the peculiar characteristic to strongly increase the shelf life of water buffalo Mozzarella cheese. To explain the mechanism of action of the gel, measurements of Ca and Na in the cheese and in the storage liquid were carried out, together with pH determination. A correlation has been found between the constant level of Ca and pH in the cheese and the prolongation of nutritional characteristics; in fact, both parameters diminish significantly in the absence of gel. At the same time, the weight of the cheese in gel remained constant for as long as 30 d. Confocal laser microscopy gave direct evidence of the persistent physical structure of proteins and lipids of Mozzarella when stored in gel.     

Relationships between flavoring capabilities,bacterial composition,and geographical origin of natural whey cultures used for traditional water-buffalo mozzarella cheese manufacture

Natural whey cultures (NWC) (n = 29) used for traditional water-buffalo Mozzarella cheese manufacture and arising from different geographical areas of production were characterized and grouped on the basis of their capability to develop neutral volatile compounds and according to their microbial diversity as revealed by molecular analysis. The flavoring properties of NWC were studied in dairy microcosms resembling the specific technological procedure used in the traditional water-buffalo Mozzarella cheese-making. Neutral volatile compounds were identified by high-resolution gas chromatography (HRGC)-mass spectrometry analysis while information on the microbial diversity occurring in the NWC was retrieved by PCR-denaturing gradient gel electrophoresis (DGGE) analysis of 16S rDNA after direct DNA extraction. Neoformation volatile substances (n = 27) were found; 23 were identified and some of them recognized as odor-conferring molecules. Eight different bands, referable to eight microbial species, were obtained by PCR-DGGE analysis of the NWC. Statistical analyses were applied to PCR-DGGE and HRGC data. Interestingly, the flavoring capabilities and the microbial diversity of the NWC proved to be closely linked and both related to the geographical origin of the NWC. These results suggested a possible use of the molecular characterization of the dairy products to support the traceability criteria of typical dairy products like water-buffalo Mozzarella cheese.     

Vatless manufacturing of low-moisture part-skim mozzarella cheese from highly concentrated skim milk microfiltration retentates

Low-moisture, part-skim (LMPS) Mozzarella cheeses were made from concentration factor (CF) 6, 7, 8, and 9, pH 6.0 skim milk microfiltration (MF) retentates using a vatless cheese-making process. The compositional and proteolytic effects of cheese made from 4 CF retentates were evaluated as well as their functional properties (meltability and stretchability). Pasteurized skim milk was microfiltered using a 0.1-microm ceramic membrane at 50 degrees C to a retentate CF of 6, 7, 8, and 9. An appropriate amount of cream was added to achieve a constant casein:fat ratio in the 4 cheesemilks. The ratio of rennet to casein was also kept constant in the 4 cheesemilks. The compositional characteristics of the cheeses made from MF retentates did not vary with retentate CF and were within the legal range for LMPS Mozzarella cheese. The observed reduction in whey drained was greater than 90% in the cheese making from the 4 CF retentates studied. The development of proteolytic and functional characteristics was slower in the MF cheeses than in the commercial samples that were used for comparison due to the absence of starter culture, the lower level of rennet used, and the inhibition of cheese proteolysis due to the inhibitory effect of residual whey proteins retained in the MF retentates, particularly high molecular weight fractions.     

Mozzarella干酪的研制

以新鲜牛乳为主要原料,通过干酪制造条件的优化研究,确定了制造Mozzarella干酪的工艺流程及主要参数,实验表明,新鲜牛乳经标准化使得酪蛋白与脂肪之比为0．84,然后加入发酵剂和凝乳酶,凝乳形成后,经切割,排乳清,并在热水中拉伸,盐渍即到成品,产品的平均脂肪和水分的含量分别为22．82％和50．74％,达到了Mozzarella干酪的质量要求。     

Effect of calcium on microstructure and meltability of part skim mozzarella cheese

The role of calcium in the microstructure of part skim Mozzarella cheese was evaluated using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Part skim Mozzarella cheeses with 4 calcium levels (control 0.65%, T1 0.48%, T2, 0.42%, and T3 0.35%) were manufactured and stored at 4 degrees C. Microstructure and meltability of cheeses were studied on d 1 and 30. The micrographs were analyzed for numbers, area, perimeter, roundness, and size of the fat particles. Reduced calcium cheeses had greater meltability and more hydrated protein matrix with greater number of fat particles (control=125, T1=193, T2=184, and T3=215 with SEM and control = 86, T1=87, T2= 125, and T3= 140 with CLSM). Further, area and perimeter of these fat particles were also greater in reduced calcium cheeses. Area, perimeter, and size of fat particles increased and their roundness decreased upon storage of 30 d. Decrease in free serum in the protein matrix of all cheeses upon refrigerated storage was evident from the CLSM. Hydrated protein network and better emulsified fat in low calcium cheeses might have improved melt properties of Mozzarella cheese.     

Cottage cheese whey as an ingredient of cottage cheese dressing mixes

The objective of this study was to formulate and develop a good quality cottage cheese dressing using acid whey as the main ingredient. Up to 72% of cottage cheese whey was used in the dressing mixes. The percentage of fat (4.10–5.05%) and total solids (19.41–20.24%) approached the desired level and was within the legal limits for regular cottage cheese. Sensory evaluation scores for flavour, body/texture and appearance were not adversely affected by the use of acid whey. The sensory evaluation scores for all four products made with whey- or skimmed milk-based dressings were higher than the commercial control.     

Simultaneous detection of cow and buffalo milk in mozzarella cheese by Real-Time PCR assay

A Real-Time PCR Allelic Discrimination TaqMan assay based on the analysis of one diagnosis position enabling the identification of cows’ and buffalo milk in dairy products was developed. Specific primers and probes were designed on the mitochondrial cytochrome b gene. In particular, primers were designed upstream and downstream the chosen diagnosis site in a well conserved region for both Bos taurus and Bubalus bubalis. Two probes were designed to specifically hybridise to B. taurus and B. bubalis sequences.     

Shelf-life extension and quality attributes of the whey cheese “Myzithra Kalathaki” using modified atmosphere packaging

The present work evaluated the effect of modified atmosphere packaging (MAP) on quality characteristics and shelf-life extension of the whey cheese “Myzithra Kalathaki” using microbiological, chemical and sensory analyses. Myzithra cheese was packaged in four different atmospheres: vacuum, 20% CO₂/80% N₂ (M₁), 40% CO₂/60% N₂ (M₂) and 60% CO₂/40% N₂ (M₃); identical cheese samples were packaged in air, taken as controls. All cheese samples were kept under refrigeration (4±0.5 °C) for 45 days. Of the four atmospheres, the M₂ and M₃ gas mixtures were the most effective for inhibiting growth of aerobic microflora and psychrotrophs in cheese samples until days 40 and 33 of refrigerated storage, respectively. Lactic acid bacteria (LAB) were part of the cheese microflora becoming dominant toward the end of the storage period regardless of packaging conditions. Enterobacteriaeceae were also part of the cheese microflora being effectively inhibited after day 35 of storage. Molds and yeasts were also totally inhibited by MAP (M₂ and M₃) gas mixtures throughout the entire storage period. Of the chemical quality indices determined, lipid oxidation varied below 0.005 absorbance at 532 nm for all treatments, except control samples for which absorbance values of 0.02 were recorded after 35 days of storage. Lipolysis did not vary significantly with type of packaging treatment while proteolysis values showed and increasing trend up to day 25 of storage and then decreased toward the end of the storage period. Sensory evaluation (odour and taste) showed that Myzithra cheese packaged under MAP (M₂ and M₃) retained good sensory characteristics for 30 days of storage while control samples were sensorily unacceptable after 10-12 days of storage.     

Preparation of nanoparticles from denatured whey protein by pH-cycling treatment

Low temperature cross-linking of denatured whey protein through pH-cycling is proposed to develop nanoparticles with controlled size and properties. Soluble polymers were produced by heating whey protein dispersions at low ionic strength and neutral pH. Nanoparticulation was induced by acidification of diluted polymer dispersions followed by pH neutralization. The effect of aggregation conditions on the physicochemical characteristics and stability of nanoparticles was studied. Nanoparticles with a diameter ranging from 100 to 300 nm were produced depending on the pH of aggregation (5.0, 5.5, 6.0), the added calcium concentration (0, 2.5, 5 mM) and the ageing time at the aggregation pH (0–75 h). The size and the turbidity of nanoparticle dispersions increased with increasing ageing time and calcium concentration. Nanoparticle voluminosity decreased with increasing calcium concentration during pH-cycling, suggesting a more compact and less porous internal structure. The stability of nanoparticles in the presence of different dissociating buffers (EDTA, urea, SDS and DTT) was evaluated and the results showed that whey protein nanoparticles were covalently cross-linked by disulphide bonds.     

Effects of protein and fat levels in milk on Cheddar cheese yield

Over a 14-month period, bulk tank milk was collected twice a week and was adjusted with cream and skim milk powder to provide six levels each of fat and protein varying from 3·0 to 4·0%. Milk samples were analyzed for total solids, fat, protein, casein, lactose and somatic cell count and were used for laboratory-scale cheesemaking. Data obtained from the milk input and the cheese output were used to determine actual, moisture adjusted, theoretical yield, and efficiency of yield. Least squares analyses of data indicated that higher cheese yields were obtained from higher fat and protein contents in milk. Higher yield efficiency was associated with higher ratios of protein to fat and casein to fat. Regression analysis indicated that a percentage increase in fat content in milk resulted in an increase of 1·23–1·37% in moisture adjusted yield in the different protein levels. For a similar increase of protein in milk, there were 1·80–2·04% increase in moisture adjusted yields in different fat levels.     

Thermodynamic incompatibility between denatured whey protein and konjac glucomannan

The current study investigated the effect of a neutral polysaccharide, konjac glucomannan, on the heat-induced gelation of whey protein isolate (WPI) at pH 7. Oscillatory rheology (1 rad/s; 0.5% strain), differential scanning calorimetry and confocal laser scanning microscopy were used to investigate the effect of addition of konjac in the range 0-0.5% w/w, on the thermal gelation properties of WPI. The minimum gelling concentration for WPI samples was 11% w/w; the concentration was therefore held constant at this value. Gelation of WPI was induced by heating the samples from 20 to 80 °C, holding at 80 °C for 30 min, cooling to 20 °C, and holding at 20 °C for a further 30 min. On incorporation of increasing concentrations of konjac the gelation time decreased, while the storage modulus (G′) of the mixed gel systems increased to ∼1450 Pa for 11% w/w WPI containing 0.5% w/w konjac gels, compared to 15 Pa for 11% w/w WPI gels (no konjac). This increase in gel strength was attributed to segregative interactions between denatured whey proteins and konjac glucomannan.     

Influence of immersion freezing in NaCl solutions and of frozen storage on the viscoelastic behavior of mozzarella cheese

ABSTRACT:  The freezing of Mozzarella cheese by immersion in NaCl solutions may be an innovative procedure for the dairy industry because it combines conveniently salting and freezing processes. In this work, the influence of this type of freezing method and of the frozen storage of samples on the viscoelastic behavior of Mozzarella cheese was studied. Slabs (2 × 10 × 10 cm³) were immersed in 23% w/w NaCl solutions (control samples: 4 °C, 90 min; frozen samples: −15 °C, 180 min). Half of the frozen samples were immediately thawed at 4 °C . The other half was stored at −20 °C for 2 mo and then was thawed at 4 °C (frozen-stored samples). Samples were stored at 4 °C and assayed at 1, 7, 14, 20, 27, 34, and 41 d. Rheological tests were carried out in oscillatory mode (parallel-plate geometry, diameter: 20 mm, gap: 1 mm, frequency: 1 Hz). Strain sweeps were run (0.001 ≤γ₀≤ 0.1) at 20, 40, and 60 °C, and temperature sweeps were run from 20 to 65 °C (1.33 °C/min, γ₀= 0.005). Similar crossover temperatures were observed after 20 d of ripening. The influence of temperature on complex viscosity was studied by an Arrhenius-type equation. Activation energy values of 15.9 ± 0.4, 14.1 ± 0.5, and 13.8 ± 0.6 kcal/mol were obtained at 41 d for control, frozen, and frozen-stored samples, respectively. Although the immersion freezing of Mozzarella cheese affects some of the studied parameters, the differences observed between frozen and frozen-stored samples with control samples were small. Therefore, it was considered that the immersion freezing might be useful for the manufacture and commercialization of Mozzarella cheese.