Milk Cheese-making Properties Research Articles

Effect of thermoresistant protease of Pseudomonas fluorescens on rennet coagulation properties and proteolysis of milk

This study aimed to investigate the effect of different activity levels of a thermoresistant protease, produced by Pseudomonas fluorescens (ATCC 17556), on the cheesemaking properties of milk and proteolysis levels. Sterilized reconstituted skim milk powder was inoculated with the bacteria, and after incubation, centrifuged to obtain a supernatant-containing protease. Raw milk was collected and inoculated to obtain a protease activity of 0.15, 0.60, and 1.5 U/L of milk (treatments P1, P4, and P10, respectively). One sample was not inoculated (control) and noninoculated supernatant was added to a fifth sample to be used as a negative control. Samples were stored at 4°C for 72 h. After 0, 48, and 72 h, the rennet coagulation properties and proteolysis levels were assessed. The protease produced was thermoresistant, as no significant differences were observed in the activity in the pasteurized (72°C for 15 s) and nonpasteurized supernatants. The chromatograms and electrophoretograms indicated that the protease preferably hydrolyzed κ-casein and β-casein, and levels of proteolysis increased with added protease activity over storage time. The hydrolysis of αS-caseins and major whey proteins increased considerably in P10 milk samples. At 0 h, the increase in the level of protease activity decreased the rennet coagulation time (RCT, min) of the samples, possibly due to synergistic proteolysis of κ-casein into para-κ-casein. However, over prolonged storage, hydrolysis of β-casein and αS-casein increased in P4 and P10 samples. The RCT of P4 samples increased over time and the coagulum became softer, whereas P10 samples did not coagulate after 48 h of storage. In contrast, the RCT of P1 samples decreased over time and a firmer coagulum was obtained, possibly due to a lower rate of hydrolysis of β-casein and αS-casein. Increased levels of protease could result in further hydrolysis of caseins, affecting the processability of milk over storage time.

Sequence-based GWAS, network and pathway analyses reveal genes co-associated with milk cheese-making properties and milk composition in Montb\xe9liarde cows

BackgroundMilk quality in dairy cattle is routinely assessed via analysis of mid-infrared (MIR) spectra; this approach can also be used to predict the milk’s cheese-making properties (CMP) and composition. When this method of high-throughput phenotyping is combined with efficient imputations of whole-genome sequence data from cows’ genotyping data, it provides a unique and powerful framework with which to carry out genomic analyses. The goal of this study was to use this approach to identify genes and gene networks associated with milk CMP and composition in the Montbéliarde breed.ResultsMilk cheese yields, coagulation traits, milk pH and contents of proteins, fatty acids, minerals, citrate, and lactose were predicted from MIR spectra. Thirty-six phenotypes from primiparous Montbéliarde cows (1,442,371 test-day records from 189,817 cows) were adjusted for non-genetic effects and averaged per cow. 50 K genotypes, which were available for a subset of 19,586 cows, were imputed at the sequence level using Run6 of the 1000 Bull Genomes Project (comprising 2333 animals). The individual effects of 8.5 million variants were evaluated in a genome-wide association study (GWAS) which led to the detection of 59 QTL regions, most of which had highly significant effects on CMP and milk composition. The results of the GWAS were further subjected to an association weight matrix and the partial correlation and information theory approach and we identified a set of 736 co-associated genes. Among these, the well-known caseins, PAEP and DGAT1, together with dozens of other genes such as SLC37A1, ALPL, MGST1, SEL1L3, GPT, BRI3BP, SCD, GPAT4, FASN, and ANKH, explained from 12 to 30% of the phenotypic variance of CMP traits. We were further able to identify metabolic pathways (e.g., phosphate and phospholipid metabolism and inorganic anion transport) and key regulator genes, such as PPARA, ASXL3, and bta-mir-200c that are functionally linked to milk composition.ConclusionsBy using an approach that integrated GWAS with network and pathway analyses at the whole-genome sequence level, we propose candidate variants that explain a substantial proportion of the phenotypic variance of CMP traits and could thus be included in genomic evaluation models to improve milk CMP in Montbéliarde cows.

Immunomodulant feed supplement to support dairy cows health and milk quality evaluated in Parmigiano Reggiano cheese production

The effects of an immunomodulant feed supplement (OmniGen-AF®) were evaluated on cow health, composition and quality of milk produced for Parmigiano Reggiano cheese production. One hundred-ninety primiparous and multiparous Holstein and Crossbred dairy cows were randomly assigned to either a control (CTR, n = 95) or a group fed 55 g/h/d of the supplement (TRT, n = 95), from dry off to 150 days in milk (DIM). Individual milk yield (MY) was recorded daily, and individual milk quality was analyzed monthly. Health events and involuntary culling were recorded. Daily feeding of the supplement did not produce any negative effect on composition and cheese making properties of milk used to produce Parmigiano Reggiano cheese. Casein content in the milk of primiparous TRT cows increased after 90 DIM, and milk cheese-making properties, like coagulation time (LDG, r’) and aptitude (LDG, type) of cows fed the supplement were enhanced. TRT cows had fewer health related events (−21%) compared to CTR group, and multiparous TRT cows tended to have a lower somatic cell score (SCS) in the first 60 DIM than CTR (−0.6 pts). The incidence of clinical mastitis was observed to be lower in the TRT Holsteins cows than CTR (4 vs 11 cases). Involuntary culling was reduced in TRT group: supplemented cows had a lower culling rate within 60 DIM (1% TRT vs 7.4% CTR) and time of culling (DIM) occurred later (102.6 and 57 DIM for TRT and CTR, respectively). These results suggest that cow health and milk quality can be improved through an appropriate nutritional strategy and the use of an immunomodulator supplement like OmniGen-AF®. This combined nutritional strategy could have important implications for strictly regulated products like Parmigiano Reggiano cheese, other PDO cheese or organic products. This strategy may provide a feeding option to better control animal health that is fundamental to satisfy the uprising consumer’s expectations in minimizing the utilization of antimicrobials.

Use of denatured whey protein in the production of artisanal cheeses from cow, goat and sheep milk

The objective of this study was to assess the potential of a whey protein (WP) heat-denaturation and recovery process adapted to small artisanal cheese plants. The effects of cheese’s milk origin (cow, goat or sheep) and cheese whey type (sweet or acid) on the recovery rates and characteristics of WP aggregates were evaluated. The influence of the WP aggregate addition and dispersion method on the cheese-making properties of milk was also investigated. Gravity separation combined with sediment drainage was compared to centrifugation for the recovery of WP aggregates, and showed similar or slightly lower recovery rates depending on milk origin. The higher WP denaturation rate in sheep whey (both sweet and acid) resulted in better protein-aggregate recovery when compared to goat or cow whey. The diameter of WP aggregates was affected by the dispersion method, and large aggregates (6.94–30.56 μm) were obtained with a rotor-stator disperser, and smaller aggregates (0.38–2.68 μm) were obtained with a valve homogenizer. Regardless of whey origin, adding larger-diameter WP aggregates to cheese milk had no negative impact on rennet-induced coagulation, whereas smaller aggregates decreased curd firmness. WP aggregates of both diameter ranges reduced curd contraction capacity, which increased the curd mass fraction and moisture after the cooking step. Adding WP aggregates to milk increased cheese yield and moisture, and the dispersion method had no influence on these parameters, suggesting that a valve homogenizer is not required, which simplifies the process for artisanal cheese production.

Effect of commercial grape extracts on the cheese-making properties of milk

Grape extracts can be added to milk to produce cheese with a high concentration of polyphenols. Four commercial extracts from whole grape, grape seed, and grape skin (2 extracts) were characterized and added to milk at concentrations of 0, 0.1, 0.2, and 0.3% (wt/vol). The effect of grape extracts on the kinetics of milk clotting, milk gel texture, and syneresis were determined, and model cheeses were produced. Whole grape and grape seed extracts contained a similar concentration of polyphenolic compounds and about twice the amount found in grape skin extracts. Radical scavenging activity was directly proportional to the phenolic compounds content. When added to milk, grape extracts increased rennet-induced clotting time and decreased the clotting rate. Although differences were observed between the extracts, the concentration added to milk was the main factor influencing clotting properties. With increasing concentrations of grape extracts, milk gels showed increased brittleness and reduced firmness. In addition, syneresis of milk gels decreased with increasing concentrations of grape extracts, which resulted in cheeses with a higher moisture content. The presence of grape extracts in milk slightly increased protein recovery in cheese but had no effect on fat recovery. With whole grape or grape seed extracts added to milk at 0.1% (wt/vol), the recovery coefficient for polyphenols was about 0.63, and decreased with increasing extract concentration in milk. Better polyphenol recovery was observed for grape seed extracts (0.87), with no concentration effect. Commercial extracts from whole grape, grape seed, or grape skin can be added to milk in the 0.1 to 0.3% (wt/vol) concentration range to produce cheese with potential health benefits, without a negative effect on cheese yield.

Effect of feeding buckwheat and chicory silages on fatty acid profile and cheese-making properties of milk from dairy cows.

Fresh buckwheat (Fagopyrum esculentum) and chicory (Cichorium intybus) had been shown to have the potential to improve certain milk quality traits when fed as forages to dairy cows. However, the process of ensiling might alter these properties. In the present study, two silages, prepared from mixtures of buckwheat or chicory and ryegrass, were compared with pure ryegrass silage (Lolium multiflorum) by feeding to 3 × 6 late-lactating cows. The dietary dry matter proportions realised for buckwheat and chicory were 0.46 and 0.34 accounting also for 2 kg/d of concentrate. Data and samples were collected from days 10 to 15 of treatment feeding. Buckwheat silage was richest in condensed tannins. Proportions of polyunsaturated fatty acids (PUFA) and α-linoleic acid in total fatty acids (FA) were highest in the ryegrass silage. Feed intake, milk yield and milk gross composition did not differ among the groups. Feeding buckwheat resulted in the highest milk fat concentrations (g/kg) of linoleic acid (15.7) and total PUFA (40.5; both P < 0.05 compared with ryegrass). The concentration of α-linolenic acid in milk fat was similar across treatments, but its apparent recovery in milk relative to the amounts ingested was highest with buckwheat. The same was true for the occurrence of FA biohydrogenation products in milk relative to α-linolenic acid intake. Recovery of dietary linoleic acid in milk remained unaffected. Feeding buckwheat silage shortened rennet coagulation time by 26% and tended (P < 0.1) to increase curd firmness by 29%. In conclusion, particularly buckwheat silage seems to have a certain potential to modify the transfer of FA from feed to milk and to contribute to improved cheese-making properties.

Coagulation properties and Nostrano di Primiero cheese yield of milk from Brown grazing cows of different k-casein genotype

Genetic variants of milk proteins affect composition, technological characteristics and, as a consequence, cheesemaking properties of milk (Jakob and Puhan, 1992; Mariani and Summer, 1999). The effects of αS1, β and k-caseins variants, on milk coagulation properties are well known (Grosclaude, 1988). Cheesemaking involving many cheese varieties showed shorter clotting and curd firming times, higher curd firmness and cheese yields with the k-casein BB variant (Van Den Berg et al., 1992;Walsh et al., 1998)......

Effects of Ultra-High Pressure Homogenization on the Cheese-Making Properties of Milk

The effects of single- or 2-stage ultra-high pressure homogenization (UHPH; 100 to 330MPa) at an inlet temperature of 30°C on the cheese-making properties of bovine milk were investigated. Effects were compared with those from raw, heat-pasteurized (72°C for 15s), and conventional homogenized–pasteurized (15 + 3MPa, 72°C for 15s) treatments. Rennet coagulation time, rate of curd firming, curd firmness, wet yield, and moisture content of curds were assessed. Results of particle size and distribution of milk, whey composition, and gel microstructure observed by confocal laser scanning microscopy were analyzed to understand the effect of UHPH. Single-stage UHPH at 200 and 300MPa enhanced rennet coagulation properties. However, these properties were negatively affected by the use of the UHPH secondary stage. Increasing the pressure led to higher yields and moisture content of curds. The improvement in the cheese-making properties of milk by UHPH could be explained by changes to the protein–fat structures due to the combined effect of heat and homogenization.

Effect of Protein Composition on the Cheese-Making Properties of Milk from Individual Dairy Cows

The objective of this study was to evaluate the effect of variations in milk protein composition on milk clotting properties and cheese yield. Milk was collected from 134 dairy cows of Swedish Red and White, Swedish Holstein, and Danish Holstein-Friesian breed at 3 sampling occasions. Concentrations of αS1-, β-, and κ-casein (CN), α-lactalbumin, and β-lactoglobulin (LG) A and B were determined by reversed phase liquid chromatography. Cows of Swedish breeds were genotyped for genetic variants of β- and κ-CN. Model cheeses were produced from individual skimmed milk samples and the milk clotting properties were evaluated. More than 30% of the samples were poorly coagulating or noncoagulating, resulting in weak or no coagulum, respectively. Poorly and noncoagulating samples were associated with a low concentration of κ-CN and a low proportion of κ-CN in relation to total CN analyzed. Furthermore, the κ-CN concentration was higher in milk from cows with the AB genotype than the AA genotype of κ-CN. The concentrations of αS1-, β-, and κ-CN and of β-LG B were found to be significant for the cheese yield, expressed as grams of cheese per one hundred grams of milk. The ratio of CN to total protein analyzed and the β-LG B concentration positively affected cheese yield, expressed as grams of dry cheese solids per one hundred grams of milk protein, whereas β-LG A had a negative effect. Cheese-making properties could be improved by selecting milk with high concentrations of αS1-, β-, and κ-CN, with high κ-CN in relation to total CN and milk that contains β-LG B.

High‐pressure‐induced changes in bovine milk: a review

High‐pressure (HP) treatment of food products is a novel processing technique during which the product is treated in a vessel of suitable strength at a high pressure, generally in the range 100–1000 MPa. As a result, several constituents and properties of the treated product are altered. HP‐induced changes in the constituents and properties of milk are arguably among the most extensive of the range of food products studied to date. HP treatment of milk induces solubilization of minerals associated with the casein micelles, denatures whey proteins and, depending on pressure, can either induce aggregation or disruption of the casein micelles. These HP‐induced changes in milk constituents affect the properties of the milk; cheesemaking properties of milk can be enhanced considerably, indicating potential application of HP treatment in this area; furthermore, encouraging results have also been reported for HP treatment of milk prior to yogurt manufacture. HP treatment of milk also affects its microflora; however, considerable variation in baroresistance between bacterial species and strains exists. Further applied research appears warranted to establish the full commercial potential of HP treatment of milk.

Effects of high pressure treatment on the yield of cheese curd from bovine milk

Cheesemaking properties of milk are affected by high pressure (HP) treatment; this study focussed on HP-induced changes in curd yield. Yield was not influenced by treatment at pressures ≤250 MPa, but at higher pressures, curd yield was increased, by up to 25% after treatment at 600–800 MPa. In parallel with increased curd yield, increased curd moisture content and reduced protein content in the whey were observed after treatment at such pressures. Denaturation of α-lactalbumin or β-lactoglobulin occurred at >400 or >100 MPa, respectively. Curd yield and curd moisture content increased and protein content in the whey decreased with increasing treatment time (0–30 min of treatment at 400 or 600 MPa). Increased curd yield is probably a result of both the incorporation of denatured whey proteins and enhanced moisture retention in the curd. HP-induced increases in curd yield may indicate possible applications of HP treatment of milk for cheese manufacture.

Robotic milking and milk quality: effects on the cheese-making properties of milk

Robotic milking systems (RMS) modify dairy herd management and therefore some aspects of production. The main results from scientific literature on RMS and cheese-making properties have been reported. The decrease in fat content, as a consequence of the increased milking frequency, is generally confirmed. The lack of specific studies on creaming properties of milk from robotic milking experiences and with different milking frequencies has been highlighted. Indications on clotting features were obtained with a different milking frequency in a traditional milking parlour; these results showed an improvement in the casein index of milk from three daily milkings. A reduction of casein exposure to the plasminogen-plasmin complex activity in the mammary gland between two consecutive milkings seems to explain this result. The effect of RMS on milk quality for cheese-making purposes was first evaluated in a two-year monitoring study in a herd representative of Po Valley dairy farms. Preliminary results from laboratory tests on bulk milk samples indicate that milk from RMS seems suitable for cheese-making processes.

Survey of ß-Lactoglobulin and α&amp;lt;sub&amp;gt;S1&amp;lt;/sub&amp;gt;-Casein polimorpbisms in Hungarian dairy sheep breeds and crosses on DNA level (short communication)

Abstract. Beta-lactoglobulin (LGB) and the Welsh αS1-casein (αS1-casein D) types have been determined using PCR-RFLP tests in DNA isolated from blood samples collected from four dairy sheep breeds (Awassi, British Milk Sheep, Tsigaia, Lacaune), from Hungarian Merinos and from various crossbreeds (AwassixMerino) F1, (MerinoxLanghe) F1, (MerinoxPleven Blackhead) F1, (MerinoxPleven Blackhead ) F1x Black East Friesian). The following LGBA frequency values have been obtained: Awassi 0.3478; British Milk Sheep 0.6857; Tsigaia 0.5650; Lacaune 0.4730; Hungarian Merino 0.6767; (Awassix Merino) F1 0.4694; (MerinoxLanghe) F1 0.7777; (MerinoxPleven Blackhead) F1 0.5945; (MerinoxPleven Blackhead) F1 x Black East Friesian 0.6026. The Welsh αS1-casein variant was found in the Hungarian Merino breed only (4 homozygous and 16 heterozygous ewes). Plans for studies on the possible effects of these milk protein types, on milk yield and composition as well as on cheese making properties ofmilk and cheese yields are outlined.

The Curd-forming Properties of Milk as Affected by the Action of Plasmin

Purified plasmin was added to skim milk at a range of levels (0.1–10 mg L-1) and the samples subsequently incubated to allow hydrolysis of casein by the enzyme. Milk clotting properties (as measured by Formagraph) and curd yield properties of the milk were measured after incubation. Increasing plasmin addition, with concomitantly increased levels of hydrolysis of casein, resulted in increased curd firming time and cutting time and reduced firming rate and final curd firmness (all P<0.001). Rennet clotting time was only increased with extensive hydrolysis by plasmin. Curd yield was reduced with increasing plasmin addition, with concomitantly increased losses of protein in whey. With low levels of enzyme addition, however, the magnitude of most effects was small. Curd moisture was unaffected by plasmin addition to milk at any level of enzyme addition. It may be concluded that extensive hydrolysis of casein by plasmin, independent of any other alterations in milk quality, has a significant influence on some milk cheesemaking properties. However, it appears that plasmin may not be responsible for changes in cheese moisture in, for example, late lactation milk.

Effect of lactation stage on the cheesemaking properties of milk and the quality of Saint-Nectaire-type cheese.

Two groups of eight multiparous cows with different calving periods (November or February) were managed in the same way during lactation. During four 4 week experimental periods distributed over 12 months, the cows were fed on a diet composed of hay and concentrate (70:30) in a restricted and controlled amount which varied according to their lactation stage, so as to cover the animals' requirements correctly. The animals' average lactation stage varied according to period from 26 to 298 d. Milk from each group was processed on two occasions during each period to make Saint-Nectaire-type cheese; the cheesemaking conditions were the same throughout. Lactation stage had an important effect on milk fat, protein and calcium contents but not on the casein: protein ratio or phosphorus content. The milk pH and the urea content were higher in late lactation. The calcium concentration of milk was higher in late lactation but the soluble fraction was higher in early lactation. Despite higher protein contents, the maximal firmness of the coagulum of late-lactation milk was not different from that of early or mid-lactation milks. pH was higher in cheeses from late-lactation milks compared with those from early and mid-lactation milks. Cheeses from early lactation milks were more yellow than the others and had a lower dry matter fat content. In sensory analysis the odour of cheeses from early and late-lactation milks was less pleasant than that of those from mid-lactation milks. Cheeses from late-lactation milks were more melting and less firm than those from early or mid-lactation milks. Their taste was more intense and more persistent. At tasting, they were less appreciated than the others. These differences were linked to increased proteolysis in the cheeses made with late-lactation milks.

Composite milk protein phenotypes in relation to composition and cheesemaking properties of milk

The effects of composite milk protein phenotypes on the composition and cheesemaking properties of milk were studied. Pooled milks from 12 selected groups of Brown cattle with particular phenotype combinations of β-casein (A2A2, A2B), κ-casein (AA, AB, BB) and β-lactoglobulin (AA, BB) were investigated. αs1-Cn BB was common to all animals. Milk collection and cheesemaking trials on a pilot scale were repeated four times during winter 1993. The interaction between all three gene loci (β-Cn, κ-Cn, β-Lg) was found to be highly significant (P < 0.001) for the contents of total protein, casein, whey protein and fat. The casein number was 0–4% (absolute) higher for β-Lg BB milk than for β-Lg AA milk. The relative amount of κ-casein consistently increased from κ-Cn AA to κ-Cn BB. The losses of fat and curd fines in the whey and moisture-adjusted cheese yield were also affected by the genotype combinations. Recovery of milk solids was 3% higher for β-Cn A2B milk than for β-Cn A2A2 milk (P = 0.010).

Restrained molecular dynamics investigation of the differences in association of chymosin to κ-caseins A and C

There is considerable interest in the relationship between milk protein polymorphism and cheesemaking properties of milk (e.g. Jakob &amp; Puhan, 1992, 1995; Jakob, 1993). For example, the B variant of κ-casein is associated with firmer cheese curds, shorter renneting times, a smaller average micelle size, higher milk casein and κ-casein concentrations and lower whey protein concentrations (Jakob, 1994; Horne et al. 1995).