Milk Coagulation Properties Research Articles

Genetic variation in bovine milk proteins: Implications for functional and nutritional properties

The six major bovine milk proteins are encoded by highly polymorphic chromosomes. Genetic variation has become a topic of interest and controversy in recent years due to supposed adverse health effects, beginning with the A2 variant of β‐casein. The functional implications of genetic variants have been well characterised, specifically heat stability and coagulation (i.e. rennet and acid) properties of milk, which have found that the B variant of β‐casein, κ‐casein and β‐lactoglobulin are the most beneficial. Genetic variants of milk proteins provide considerable potential to create new dairy products to add value to milk.

Effect of protein polymorphisms on milk composition, coagulation properties, and protein profile in dairy sheep

The objective of this study was to quantify the effect of protein polymorphisms on milk composition, coagulation properties, and protein profile in dairy sheep from a New Zealand flock. A total of 470 test-day records, from 147 lactating ewes, were used in the statistical analyses. Protein polymorphisms observed in the RP-HPLC were self-named for purposes of the present study. Data were analyzed using a mixed linear model, including the fixed effects of ewe age, litter size, coat-colour, and stage of lactation, and, as a covariate, deviation from the median lambing date of the flock. The effects of protein polymorphisms were added to the model, one at a time. Protein polymorphisms were significantly (p < 0.05) associated with milk composition and protein profile. Polymorphisms of β-lactoglobulin were significantly associated with milk heat stability, being AB type more heat stable than AA. The other processability traits were not significantly affected by protein polymorphisms. Further studies are required to confirm the protein variants and the properties of individual protein polymorphisms.

Impact of ultrasonic and heat treatments on the physicochemical properties and rennet-induced coagulation characteristics of milk from various species

This study investigates the effects of heat and ultrasonic treatments on the physicochemical parameters and rennet-induced coagulation properties of milk from a variety of species, including cow, goat, buffalo, and donkey. Milk samples were subjected to heat treatments at different temperatures (65 °C, 80 °C, 90 °C, 100 °C) and ultrasonic treatment at varying power levels (200 W, 400 W, 600 W, 800 W, 1000 W). The results revealed that changes in turbidity, particle size, zeta potential, secondary structure, and surface hydrophobicity were altered by both ultrasonic and heat treatments, as well as the kind of milk. Ultrasonic treatment of cow milk decreased α-helix content while increasing β-turn content. Under similar ultrasonic treatment, goat milk showed a considerable increase in β-sheet content, whereas β-turn and random coil contents decreased compared to control samples. Notably, the water-holding capacity of gels formed from all four types of milk increased significantly with the intensity of ultrasonic and heat treatments. The hardness of buffalo milk gels increased significantly after ultrasonic and thermal treatments, ranging from 63 °C for 30 min to 90 °C for 15 min, but the hardness of cow and goat milk gels increased in varying degrees compared to their control samples. Furthermore, gels from cow and goat milk had higher storage modulus (G’) and loss modulus (G’’) than those from buffalo and donkey milk, and changes in G’ and G’’ from the examined milk were altered by ultrasonic and heat treatments. These findings offer important insights into refining milk processing procedures to improve dairy product quality and usefulness.

Analyzing Runs of Homozygosity Reveals Patterns of Selection in German Brown Cattle.

An increasing trend in ancestral and classical inbreeding coefficients as well as inbreeding depression for longevity were found in the German Brown population. In addition, the proportion of US Brown Swiss genes is steadily increasing in German Browns. Therefore, the aim of the present study was to analyze the presence and genomic localization of runs of homozygosity (ROH) in order to evaluate their associations with the proportion of US Brown Swiss genes and survival rates of cows to higher lactations. Genotype data were sampled in 2364 German Browns from 258 herds. The final data set included 49,693 autosomal SNPs. We identified on average 35.996 ± 7.498 ROH per individual with a mean length of 8.323 ± 1.181 Mb. The genomic inbreeding coefficient FROH was 0.122 ± 0.032 and it decreased to 0.074, 0.031 and 0.006, when genomic homozygous segments > 8 Mb (FROH>8), >16 Mb (FROH>16) and >32 Mb (FROH>32) were considered. New inbreeding showed the highest correlation with FROH>32, whereas ancestral inbreeding coefficients had the lowest correlations with FROH>32. The correlation between the classical inbreeding coefficient and FROH was 0.572. We found significantly lower FROH, FROH>4, FROH>8 and FIS for US Brown Swiss proportions <60% compared to >80%. Cows surviving to the 2nd, 4th, 6th, 8th, and 10th lactation had lower genomic inbreeding for FROH and up to FROH>32, which was due to a lower number of ROH and a shorter average length of ROH. The strongest ROH island and consensus ROH shared by 50% of the animals was found on BTA 6 at 85-88 Mb. The genes located in this genomic region were associated with longevity (NPFFR2 and ADAMTS3), udder health and morphology (SLC4A4, NPFFR2, GC and RASSF6), milk production, milk protein percentage, coagulation properties of milk and milking speed (CSN3). On BTA 2, a ROH island was detected only in animals with <60% US Brown Swiss genes. Genes within this region are predominantly important for dual-purpose cattle breeds including Original Browns. For cows reaching more than 9 lactations, an exclusive ROH island was identified on BTA 7 with genes assumed to be associated with longevity. The analysis indicated that genomic homozygous regions important for Original Browns are still present and also ROH containing genes affecting longevity may have been identified. The breeding of German Browns should prevent any further increase in genomic inbreeding and run a breeding program with balanced weights on production, robustness and longevity.

Usefulness of Moringa oleifera seed extract as Coagulant for the production of fresh camel cheese

The current study aimed to enhance the coagulation properties of camel milk using enzymatic extracts derived from Moringa oleifera seeds. Experiments were conducted to evaluate the clotting activities of Moringa extract on camel milk and compare them with cow milk. Our results regarding the characterisation of the enzymatic extract showed an extraction yield of 54.3±1.8%. The optimum coagulation conditions were determined to be pH 5 and a temperature of 55°C. In addition, the enzymes exhibited substantial clotting activity (2.54 RU) on both camel and cow milk. The cheese samples showed significant oxidative and antibacterial activity.

Estimation of genetic parameters for production, composition and processability of milk from dairy sheep in a New Zealand flock

ABSTRACT This paper aimed to estimate the heritability and genetic correlations for processability (milk coagulation properties, cheese yield, and heat stability), milk production, and milk composition of dairy sheep in a New Zealand flock. Test-day records from 169 ewes were obtained during the 2021–2022 season. Heritability estimates for yield traits (milk, fat, protein, and lactose yield) were moderate and ranged from 0.33 to 0.38. Whereas heritability estimates for processability traits were lower and ranged from 0.17 to 0.27. The genetic correlations indicated that poorer milk coagulation properties were associated with lower mammary health indicated by higher SCS, higher pH, and lower lactose content. Additionally, a higher ratio of casein to calcium i.e. lower availability of soluble calcium was associated with poorer milk coagulation properties. Higher yields of milk, fat, protein, and lactose were associated, but to a smaller degree, with better MCP. It is proposed that genetic improvement of dairy sheep for higher yields of fat and protein, and for lower SCS, could indirectly improve milk processability for cheese-making. However, it is recommended that larger studies involving more dairy sheep flocks are conducted to validate the present results before developing a selection index for this industry.

Multiomics analysis revealed that the metabolite profile of raw milk is associated with the lactation stage of dairy cows and could be affected by variations in the ruminal microbiota

The nutritional components and quality of milk are influenced by the rumen microbiota and its metabolites at different lactation stages. Hence, rumen fluid and milk samples from 6 dairy cows fed the same diet were collected during peak, early mid- and later mid-lactation. Untargeted metabolomics and 16S rRNA sequencing were applied for analyzing milk and rumen metabolites, as well as rumen microbial composition, respectively. The levels of lipid-related metabolites, L-glutamate, glucose-1-phosphate and acetylphosphate in milk exhibited lactation-dependent attenuation. Maltol, N-acetyl-D-glucosamine, and choline, which are associated with milk flavor or coagulation properties, as well as L-valine, lansioside-A, clitocine and ginsenoside-La increased significantly in early mid- and later mid-lactation, especially in later mid-lactation. The obvious increase in rumen microbial diversities (Ace and Shannon indices) were observed in early mid-lactation compared with peak lactation. Twenty-one differential bacterial genera of the rumen were identified, with Succinivibrionaceae_UCG-001, Candidatus Saccharimonas, Fibrobacter, and SP3-e08 being significantly enriched in peak lactation. Rikenellaceae_RC9_gut_group, Eubacterium_ruminantium_group, Lachnospira, Butyrivibrio, Eubacterium_hallii_group, and Schwartzia were most significantly enriched in early mid-lactation. In comparison, only 2 bacteria (unclassified_f__Prevotellaceae and Prevotellaceae_UCG-001) were enriched in later mid-lactation. For rumen metabolites, LPE(16:0), L-glutamate and L-tyrosine had higher levels in peak lactation, whereas PE(17:0/0:0), PE(16:0/0:0), PS(18:1(9Z)/0:0), L-phenylalanine, dulcitol, 2-(methoxymethyl)furan and 3-phenylpropyl acetate showed higher levels in early mid- and later mid-lactation. Multiomics integrated analysis revealed that a greater abundance of Fibrobacter contributed to phospholipid content in milk by increasing ruminal acetate, L-glutamate and LysoPE(16:0). Prevotellaceae_UCG-001 and unclassified_f_Prevotellaceae provide substrates for milk metabolites of the same category by increasing ruminal L-phenylalanine and dulcitol contents. These results demonstrated that milk metabolomic fingerprints and critical functional metabolites during lactation, and the key bacteria in rumen related to them. These findings provide new insights into the development of functional dairy products.

Influence of αs1-casein genetic variant in buffalo milk and rennet coagulation properties

Buffalo milk, recognized for its rich composition, including higher levels of fat, lactose, protein, and ash when compared to cow milk, has been insufficiently studied considering its genetic diversity within the buffalo population in Serbia. This study focuses on the analysis of the CSN1S1 472G&gt;C variant and its potential impact on rennet coagulation properties, critical for cheese production. Rennet coagulation parameters (rennet coagulation time (RCT), setting time (ST), aggregation rate (AR), and gel firmness (GF)), along with fresh curd yield (Yf), were examined in both, raw and high heat-treated buffalo milk. Genotyping results, obtained through Sanger sequencing of blood samples from 30 female buffaloes, revealed the presence of three CSN1S1 472G&gt;C genotypes: GG, GC, and CC. The rheological measurements, conducted using dynamic small amplitude oscillatory rheology (SAOR), indicated significant statistical differences (p&lt;0.05) among the tested parameters for these CSN1S1 472G&gt;C genotypes in both raw and heat-treated buffalo milk. In addition, the influence of genotype on the yield of fresh curd in fresh and thermally treated milk was studied. These results can contribute to optimization in the process of production and processing of buffalo milk, emphasizing the importance of understanding the genetic factors in the composition of buffalo milk and its technological properties.

Effect of chymosin/pepsin ratio on milk coagulation and physical properties of model cheese

Chymosin and pepsin are the two major enzymes in coagulants for the cheese industry. They affect milk coagulation properties, curd composition, casein hydrolysis and the consequent development of cheese texture. Limited knowledge is available on the effect of the chymosin/pepsin ratio on the mentioned factors. This study aimed (1) to better understand the effect of chymosin/pepsin ratio on milk coagulation properties, casein hydrolysis, rheological and textural properties of model cheese during storage, and (2) to link casein hydrolysis to the rheological and textural properties. For this purpose, coagulants were prepared in which the ratio between the two enzymes was systematically varied. Our results showed that even when milk clotting activity was standardized, coagulants with different chymosin/pepsin ratios had a significant effect on curd firming rate and final firmness, which could be attributed to the different specificity of chymosin and pepsin for hydrolyzing κ-CN. During 4 weeks of storage, the chymosin/pepsin ratio influenced the hydrolysis of αs1-CN, and the subsequent properties of the protein network and the cheese texture. For coagulants with a higher proportion of pepsin, less intact αs1-CN and a higher degree of casein hydrolysis (expressed as protein fraction soluble at pH 4.6) were found. Correspondingly, the cheese had a weaker and less brittle network, and was softer, less elastic and more sticky. Commercial calf rennet showed more extensive hydrolysis of αs1-CN than other coagulants, which led to the weakest protein network and the softest cheese. The present study's findings can be used to control and design cheese with desired textures. For example, coagulants with varying chymosin/pepsin ratio or from a specific source can be used to modulate the casein hydrolysis.

Impact of genetic κ-casein variants (A, B, E) on chymosin-induced milk coagulation properties: Application of a new LC–MS-based genotyping method

This study evaluated the impact of κ-casein (κ-CN) protein phenotype (AA (n = 18), AB (n = 18), AE (n = 5), BB (n = 3)) in the raw milk of 44 individual Holstein cows from a single farm on coagulation properties using diffusion wave spectroscopy. κ-CN variants were analyzed using a newly developed LC–MS method in individual milk samples, and relative milk protein fractions were quantified by LabChip-analysis. κ-CN fractions expressed in the percentage of total milk protein, total casein, and β- and κ-CN were then calculated. The gross composition of the individual milk samples and variation between individual cows was analyzed and was rather large, as expected. Traits were analyzed using an ANCOVA model with pH as a covariate.Our results showed that mean percentages of κ-CN fractions increased for κ-CN phenotypes in the order AA < AE < AB < BB. Rennet coagulation time was slightly affected, but curd firmness was significantly affected by κ-CN phenotype (BB > AE > AB > AA) when controlling for pH.

Factors affecting the coagulation of milk protein during quark cheese processing in Vietnam

In recent years, cheese consumption in Vietnam is markedly rising, leading to the attention of local milk processors on cheese making. Quark-type cheese, a traditional food in Central Europe, is a type of well-known acid-coagulated cheese product. Milk coagulation properties (MCPs) play an important role to the success of the cheese-making process and are influenced by different parameters. In this study, the quality of raw milk for cheese making and the coagulation conditions in quark-type cheese processing were investigated. Raw milk collected from Phu Dong dairy farm met the requirement of Vietnamese standard for cheese making. The appropriate conditions for coagulation were identified: the heat treatment of milk at 60°C for 15 minutes, coagulation temperature at 40oC and pH 5.5, CaCl2 concentration at 0.04g/l. Under these conditions, a short coagulation time (72.33 seconds) and high curd yields (50.70%) were obtained. These results suggested that quark-type cheese using raw milk in Vietnam could be successfully developed at larger scale.

Associations between Milk Coagulation Properties and Microbiological Quality in Sheep Bulk Tank Milk.

This study conducted a seasonal analysis of bulk tank milk from 77 sheep farms to establish relationships between the concentration of major microbial groups and milk coagulation properties. The investigated milk traits included composition (pH, fat, casein, lactose), coagulation properties (curd firmness: A60-, rennet clotting time: RCT-, curd firming time: k20-, curd yield: CY-), and somatic cell score (SCS). The main microbial groups analyzed were total mesophilic bacteria (SPC), thermodurics (THERMO), psychrotrophs (PSYCHRO), Pseudomonas spp. (PSEUDO), lactic acid bacteria (LAB), catalase-negative gram-positive cocci (GPCNC), Escherichia coli (ECOLI), coliforms other than Escherichia coli (COLI), coagulase-positive staphylococci (CPS), coagulase-negative staphylococci (CNS), and spores of lactate-fermenting Clostridium (BAB). Mixed linear models were used to explore associations between coagulation properties and the aforementioned variables. Results demonstrated that incorporating microbial loads into the models improves their fit and the relative quality of the outcomes. An important seasonality is demonstrated by an increase in CY and A60, along with a decrease in RCT and k20 during autumn and winter, contrasting with spring and summer. BAB concentration resulted in a reduction of A60 and an increase in RCT, whereas SPC concentration led to an enhancement of A60 and a reduction in RCT. An increase in GPCNC concentration was associated with an increase in k20 and a decrease in CY.

Prediction of sheep bulk milk coagulation properties from mid-infrared spectral data

The technological features of milk are essential for cheese manufacturing. This is particularly true for Italy, where most of the milk produced by sheep is intended for cheese production. The possibility to evaluate technological characteristics and coagulation aptitude of milk in advance, before any treatment, is crucial for decision-making at industry level. In the present study, we tested the ability of mid-infrared spectroscopy for prediction of coagulation traits (rennet coagulation time and curd firmness) by using more than 4000 bulk milk samples of 344 sheep herds. The models developed with a partial least square regression showed that spectral data points can be successfully used to predict the two traits. The coefficient of determination in external validation was 0.42 for rennet coagulation time and 0.28 for curd firmness, indicating that sheep milk delivered to dairies can undergo a preliminary screening only to assess the expected coagulation time. This finding will allow manufacturers to evaluate the milk received from farmers. Further investigation will be need to improve the prediction of rennet coagulation time that can be coupled with composition traits to define premiums or penalties in the payment system.

Re-sequencing of the casein genes in Swedish Red cattle giving milk with diverse protein profiles and extreme rennet coagulation properties

Impaired rennet coagulation properties in milk could lead to prolonged processing times and production losses. Heritability for milk coagulation has previously been estimated to be 0.28 to 0.45, indicating that genetic selection can be used to manipulate this trait. The CN proteins are expressed by the genes CSN1S1, CSN2, CSN1S2, and CSN3 and are located on bovine chromosome 6. To better understand the effect of genetic variation in the CN genes on milk coagulation, blood and milk samples from 30 Swedish Red Dairy Cattle (RDC) with divergent coagulation properties were investigated. DNA from the 30 cows was sequenced for the CN genes to determine the theoretical AA sequence and to look for genetic variation in the untranslated regions. The aim is to confirm the protein genetic variants previously reported, while searching for additional genetic variation in the CN genes of 30 RDC. We observed genetic variation in 116 SNPs in the known CN genes where 10% of the SNPs are exon variants and the remaining 90% are intron variants. A total of 2.5% of the SNPs are found in the 5′- or 3′-untranslated region (UTR) regions of the exons; 2% are synonymous variants and 6% are missense variants that concurred with the known protein variants for CSN1S1, CSN2, and CSN3. Furthermore, 6% of the SNPs are splice polypyrimidine tract intron variants. The 2 genetic variants in the 5′- and 3′-UTR in CSN1S1 and CSN3 are found with protein variants CSN1S1C and CSN3B. Because both UTR variants are associated with gain and loss of micro RNA and transcription factors, this could explain differences in expression of the genetic protein variants. Preliminary chi-squared analysis and comparison with previous GWAS studies showed potential connections between the identified SNPs and coagulation properties of milk. By advancing the knowledge of the connection between the DNA sequence and the functional properties of the CN proteins, we hope to learn more about the cheese coagulation properties of milk from RDC.

Associations of lameness with milk composition, fatty acid profile, and milk coagulation properties in mid-lactation high-yielding Holstein cows

Lameness, an animal welfare and profitability related problem in dairy industry, was evaluated on 126 multiparous Estonian Holstein cows on a 5-point scale; score three or above indicated lameness. Milk samples of the cows were analysed for basic composition, content of mineral elements, fatty acid (FA) profile and coagulation properties (MCP). Lame cows had lower milk yield and a lower milk protein and milk fat yield compared to non-lame cows. MCP and content of mineral elements were not affected by lameness. The concentrations of most individual milk FA, their groups formed by chain length, degree of saturation or by origin were not affected by the lameness. Lameness was associated with a higher concentration of odd- and branched-chain fatty acids and C18:0. Milk from lame cows is suitable for consumers as lameness did not impair nutritional value nor MCP of the milk.

Effect of jujube pulp on acid- and rennet-induced coagulation properties of milk

Effect of jujube pulp on acid- and rennet-induced coagulation properties of milk

A comprehensive study on milk composition and coagulation properties from six endangered native Norwegian cattle breeds

Six cattle breeds native to Norway, have for almost half a century been at risk of extinction. Due to their small population sizes, they have hardly been improved by breeding for many decades. Still, the endangered breeds represent a source of genetic diversity with special milk qualities compared to the modern breed, Norwegian red (NRF). This study reports for the first time a detailed overview of their milk composition. Milk from seven native breeds, in total 200 individuals, were included in the study. Rare genetic variants of αs1-and αs2-casein, and β-casein A1 and κ-casein B were more prevalent in milk form the endangered breeds compared to NRF. Moreover, milk from these six breeds showed better renneting properties and lower incidences of non-coagulating milk, compared to the NRF milk, which showed better acid coagulation properties. This study shows the potential for native breeds in small-scale production of high-quality rennet cheeses.

Estimating the Effect of the Kappa Casein Genotype on Milk Coagulation Properties in Israeli Holstein Cows.

In Israel, about 26% of produced milk is used to produce hard cheeses and 29% for soft cheeses. Milk with preferred coagulation properties requires a shorter coagulation time and yields a higher curd firmness than milk with inferior coagulation properties. Studies have shown that milk from cows with the B allele of kappa casein (κ-CN) produces more cheese than milk from those with A and E alleles. There is evidence that milk from AE or EE genotype cows is unsuitable for cheese production. In the early 1990s, the proportion of the B allele in Israeli Holstein cattle was about 17%, similar to its prevalence in the Holstein population worldwide. In recent years, however, its proportion has increased to about 40%. We analyzed milk coagulation properties as a function of the cow's κ-CN genotype, including time in minutes until the beginning of coagulation and curd firmness after 60 min-measured in volts via an optigraph device and scored on a scale of 0-4 by a laboratory technician. Cow selection was based on their sire's genotype, so that there would be sufficient genotypes that include the rare E allele. A total of 359 cows were sampled from 15 farms: 64 with genotype AA, 142 with AB, 41 with AE, 65 with BB, and 47 with BE. Data were analyzed via the general linear model procedure of SAS. We found the following: (a) There were significant differences between genotypes for optigraph-measured curd firmness. In a multi-comparison test, the BB genotype gave the highest curd firmness, and AB and BE showed a significant advantage compared to AA and AE (9.4, 8.6, 8.4, 6.9, 6.8 V, respectively). Assuming a frequency of about 55% for the A allele, about 30% of the milk delivered to dairy plants comes from AA cows. (b) There was a significant difference between the genotypes in technician-observed curd firmness, with BB scoring significantly higher than AA and AE. (c) The optigraph-measured curd firmness was significantly higher for milk from primiparous cows as compared to milk from second, third, or fourth lactation cows (8.9, 7.8, 7.9, 7.7 V, respectively). The technician-observed curd firmness was significantly higher for primiparous vs. multiparous cows. There was a clear advantage in curd firmness for genotypes that included the B allele compared to those with AA and AE genotypes. We can increase the proportion of the B allele in the population by insemination of cows using bulls with the genotypes AB and BB. This factor should therefore be included in the selection index.

Effects of calf rennet, and microbial and plant coagulants on rheological properties of milk for Grana Padano PDO cheese production

The effects of calf rennet, and microbial and plant coagulants on milk coagulation properties (MCP) measured through lactodynamographic analysis were investigated. Each coagulant was tested at 7 different dilutions: one reference dilution, 3 lower dilutions (−30%, −20%, and −10% IMCU L−1 milk) and 3 greater dilutions (+10%, +20%, and +30% IMCU L−1 milk). Sources of variation of rennet coagulation time (RCT, min), curd-firming time (k20, min), and curd firmness (a30, mm) were investigated through a linear model that included the effects of coagulant, dilution, and their interaction. All the effects were highly significant in explaining the variability of the studied traits (P <0.001). In particular, calf rennet resulted in shorter k20 and greater a30 than microbial and plant coagulants. Dilution effect was linearly associated with MCP, whereby a decreasing amount of coagulant led to a lengthening of RCT and k20, whereas a less clear association was observed for a30.

Exploring the relationships between coagulation, composition, and hygienic quality of bulk tank milk from Manchega sheep

Milk from Manchega sheep is the raw material for the elaboration of Protected Designation of Origin (PDO) Queso Manchego, a hard-pressed cheese with one of the most established quality marks on the market worldwide. For this reason, milk quality control in this breed is one of the main targets of the dairy sheep sector. However, pricing systems still continue to apply criteria based only on milk composition and the current legislation on food hygiene. The aim of this study is to explore bulk tank sheep milk quality, estimating milk coagulation properties and their relationship with composition, somatic cell counts, and differential microbiological quality. For this purpose, 308 bulk tank milk samples were collected with seasonal periodicity, and analyses were performed for the aforementioned traits. The obtained results highlight the variability in composition, microbiology, and coagulation properties in different samples, which prevents clear relationships between milk quality parameters. However, there was evidence of a group of milk samples whose coagulation would be desirable for cheesemaking, based on values for fat, protein and total solids. Outcomes also stand out casein content as an important parameter to affect curd yield, proving the interest of using casein as trait for genetic improvement in dairy sheep breeds.