Beta-Casein

The A1 and A2 variants of bovine β-casein (CSN2) have gained attention in the dairy industry due to potential health effects. The A1 variant, prevalent in Holstein-Friesian cattle, is a major source of β-casomorphin-7 (BCM-7)-an opioid-like peptide released during digestion and associated with lower digestive comfort. In this study, β-casein A1 and A2 variants and BCM-7 levels were quantified in raw milk and three commonly consumed dairy products (pasteurized milk, UHT milk, and milk powder) using ELISA. The samples came from dairy plants within a single operating zone. The A1 variant was significantly more frequent (13.69-22.41 ng/mL) than the A2 variant (8.10-12.60 ng/mL), although the local Holstein cattle population had a higher frequency of the A2 allele (63%) than A1 (37%). This discrepancy could be due to a more efficient expression of the A1 allele in cows with heterozygous or A1A1 genotypes. BCM-7 levels were low and did not vary significantly with CSN2 genotype or processing method. These results provide new insights into the composition of dairy products and contribute to the ongoing debate on the health implications and consumer acceptance of milk with the A1 β-casein variant.

Variant A1 of bovine beta-casein (CSN2) is known for producing beta-casomorphin-7 (BCM7), which is an opioid-like peptide released during gastrointestinal digestion. The aim of the study was to measure how much A1 and A2 protein variants occur in the milk of cows with different CSN2 genotypes. In a population of 113 A1A2 Holstein-Friesian cows, using the ELISA method, it was found that variant A2 was present at low content in milk (mean 6.31±3.09 ng/mL), but variant A1 reached almost seven times higher concentration (43.40 ng/mL±15.68 ng/mL). This unbalanced expression of the CSN2 alleles was not associated with the single nucleotide polymorphism within the 5' flanking sequence known as beta-casein enhancer (BCE). Moreover, the origin of allele A1 (whether inherited from a sire or dam) did not explain its overexpression. Furthermore, using qRT-PCR, it was shown that the mRNA levels of the CSN2 A1 and A2 alleles are at similar levels in the milk somatic cells of 16 A1A2 cows, suggesting that the unbalanced expression of CSN2 alleles could be determined by post-transcriptional events. Two SNPs were identified within the CSN2 3' UTR in 109 cows with A1A2 genotype. The STarMiR software was used to predict microRNA targets and indicated that G/A was located within the canonical seed sites of bta-miR-145, potentially affecting miRNA-mRNA binding and translational repression of the CSN2 variant.

In the last two decades, the bovine A1 variant of beta-casein has attracted attention in the dairy industry as a source of beta-casomorphin-7, an opioid-like peptide with potentially
harmful effects on human health. Because the origin of this variant is unknown, the aim of the study was to investigate its occurrence in different species of the Bovidae family. Blood samples were taken from 137 animals belonging to 17 Bovidae species. All animals were
genotyped for the beta-casein locus using the Illumina Bovine MDv2 Chip. The results showed that the A1 allele was present in Bos taurus cattle, including primitive cattle (Watussi and Ukrainian Grey) and a modern dairy breed (Holstein). In Dahomey cattle, two heterozygous A1A2 individuals were found. In all remaining species, no animal carrying the A1 allele of beta-casein was identified. It can be concluded that the A2 allele is ancestral to the A1 allele and was spread especially among modern dairy cattle.

La mayor parte de la superficie de la region central deArgentina se halla cubierta por vegetacion natural y el manejo al que han sido sometidas hasta la actualidad las ha transformado en areas de baja produccion y dificil manejo. El pastoreo por ganado domestico y los incendios han contribuido al deterioro de estos ecosistemas, que en la actualidad presentan una fuerte invasion de lenosas y pajonal. Una tecnica propuesta ha sido el rolado selectivo que aplasta y fragmenta la vegetacion lenosa e incrementa el area de pastizales. El objetivo de este trabajo es evaluar los efectos del rolado sobre la vegetacion y la retencion de agua en el suelo en un area de renoval y transferir los resultados alcanzados sobre el control las lenosas y la conservacion del suelo con la finalidad de recuperar estas areas degradadas. En un area cubierta de fachinal se realizo un rolado selectivo y se establecieron 2 tratamientos: rolado y testigo. Cada tratamiento tuvo tres repeticiones (transectas) sobre...

La mayor parte de la superficie de la region central deArgentina se halla cubierta por vegetacion natural y el manejo al que han sido sometidas hasta la actualidad las ha transformado en areas de baja produccion y dificil manejo. El pastoreo por ganado domestico y los incendios han contribuido al deterioro de estos ecosistemas, que en la actualidad presentan una fuerte invasion de lenosas y pajonal. Una tecnica propuesta ha sido el rolado selectivo que aplasta y fragmenta la vegetacion lenosa e incrementa el area de pastizales. El objetivo de este trabajo es evaluar los efectos del rolado sobre la vegetacion y la retencion de agua en el suelo en un area de renoval y transferir los resultados alcanzados sobre el control las lenosas y la conservacion del suelo con la finalidad de recuperar estas areas degradadas. En un area cubierta de fachinal se realizo un rolado selectivo y se establecieron 2 tratamientos: rolado y testigo. Cada tratamiento tuvo tres repeticiones (transectas) sobre...

Genetic variants of -lactoglobulin (-LG) A and B have been associated with milk production and composition, which can vary between dairy breeds. The aim of this study was to determine the relationship of genetic variants of -LG with milk composition and production of Holstein cows (H) and Tropical Milking Criollo (TMC). Three hundred and fifty milk samples of H cows and 64 of TMC were characterized. Individual information on production and reproduction records of both breeds was collected. The chemical composition of each sample was determined by mid-infrared spectroscopy and somatic cell count (SCC) by flow cytometry. An analysis of variance was conducted with mixed models to study the effect of -LG phenotype on the chemical composition of milk, SCC, milk production, fat and protein adjusted to 305 d and milk yield at the day of sampling. In the statistical model, the random effect of the cow's father and the fixed effects herd-year-season, phenotype and number of birth were included, besides the covariates days in milk and cow age. -LG phenotype was found to have a significant effect on chemical composition of milk. The percentage of fat, protein, nonfat and total solids were significantly (p0.05) higher in BB phenotype for both breeds. The milk yield/production fitted to 305 d was higher (p0.05) for AA phenotype of H cows.

Uma revisão sobre o efeito do hexametafosfato de sódio na estrutura das micelas de caseína A review on the effect of sodium hexametaphosphate on the structure of casein micelles Una revisión sobre el efecto del hexametafosfato de sódio en la estructura de las micelas de caseína

O hexametafosfato de sódio, da sigla em inglês, SHMP, é comumente utilizado para controlar a acidez, estabilizar e retardar a gelatinização de produtos lácteos e na fusão de queijos na fabricação de queijos fundidos. Este sal dissocia as micelas de caseína presentes no leite, sequestrando íons de cálcio. Em estudos anteriores, o SHMP, se mostrou o mais eficiente em dissociar as micelas de caseína, em comparação a outros sequestrantes de cálcio. Variações na temperatura e no pH, afetam o equilíbrio mineral-proteína e interações eletrostáticas, levando a desestruturação das micelas de caseína. Visto que a turbidez de uma suspensão coloidal, como o das micelas de caseína no leite, está relacionada ao tamanho e as propriedades de espalhamento das partículas dispersas, espera-se que as dissociações das micelas de caseína reduzam a turbidez do leite. Esta revisão descreve as estratégias recentemente desenvolvidas para superar desafios relacionados a turbidez do leite, utilizando SHMP, mas...

Milk is a fundamental feed of all newborn mammals and a good source of proteins, fatty acids, micro elements, calcium, phosphorus, among others, for non-lactating humans. As world demand for foods increases, so does the concern and requirements of consumers for food quality and safety. In view of evidences of possible pathologies associated to milk consumption, detractors of the dairy industry have appeared, making use of these arguments. Research on the risks associated to milk ingestion has been conducted on the last twenty years and the existence of specific milk protein variants able to cause disorders such as milk intolerance, diabetes mellitus type 1, ischemic heart disease and food allergies, has been established. The determination of casein genetic variants and the association of the A1 beta-casein with human health disorders represent an opportunity, for the farmers to select replacements, retaining those cows with the desirable alleles, and also for the dairy industry to obtain safer dairy products. As a result, all the dairy supply chain, from producers to consumers, will be benefited.

For over 20 years, bovine beta-casein has been a subject of increasing scientific interest because its genetic A1 variant during gastrointestinal digestion releases opioid-like peptide β-casomorphin-7 (β-CM-7). Since β-CM-7 is involved in the dysregulation of many physiological processes, there is a growing discussion of whether the consumption of the β-casein A1 variant has an influence on human health. In the last decade, the number of papers dealing with this problem has substantially increased. The newest clinical studies on humans showed a negative effect of variant A1 on serum glutathione level, digestive well-being, cognitive performance score in children, and mood score in women. Scientific reports in this field can affect the policies of dairy cattle breeders and the milk industry, leading to the elimination of allele A1 in dairy cattle populations and promoting milk products based on milk from cows with the A2A2 genotype. More scientific proof, especially in well-designed clinical studies, is necessary to determine whether a little difference in the β-casein amino acid sequence negatively affects the health of milk consumers.

Objective:: Kappa-casein (CSN3) variant B is a widely known marker of milk processing traits. Betacasein (CSN2) is a source of the opioid-like peptide β-casomorphins-7 (BCM-7), which is yielded by the successive in vitro gastrointestinal proteolytic digestion of the CSN2 A1 variant but not A2. Epidemiological and animal model studies suggest that BCM-7 may be a potential risk factor in the etiology of some human diseases. Because breeding companies and dairy plants have been encouraged to use CSN3 BB bulls for insemination of cows for over 30 yr, it was hypothesized that bulls of CSN3 BB genotype are spreading the undesirable A1 allele of CSN2 in the population of Holstein bulls. Materials and Methods:: Among 519 Holstein bulls, 109 bulls were selected as having the CSN3 BB genotype. These bulls were then genotyped for the CSN2 polymorphism. All bulls had an official breeding index PF (production and functionality). Results and Discussion:: The frequency of undesirable allele A1 of CSN2 locus was relatively high at 31.7%. Among 109 bulls with the CSN3 BB genotype, although 50 bulls had the desirable CSN2 A2A2 genotype, 10 carried the undesirable CSN2 A1A1 genotype. These 10 bulls (CSN3 BB and CSN2 A1A1) had the lowest average PF breeding index. Implications or Applications:: Bulls with CSN3 BB genotype and the CSN2 A2 variant should be preferred in breeding schemes because they simultaneously improve general breeding value and cheese-making properties and promote milk without negative implications on human health.

bovine peptidoglycan recognition protein 1 (pglyRp1) is an important receptor that binds to murein peptidoglycans (pgn) of grampositive and gram-negative bacteria and is, therefore, involved in innate immunity. the snp t>c rs68268284 located in the 1st exon of the PGLYRP1 gene was identified by the PCR-RFLP method in a population of 319 Holstein cows. Somatic cell count (scc) was measured 7-10 times in each of three completed lactations to investigate whether the PGLYRP1 polymorphism is associated with scc. using the GLM model, it was found that cows with the TT genotype showed significantly lower somatic cell counts than those with the CC genotype during the first lactation (P = 0.023). Moreover, during lactations 1-2 and 1-3, cows with the TT genotype reveal significantly lower SCC than CT heterozygotes, at P = 0.025 and P = 0.006, respectively. Computer-aided analysis showed that rs68268284 polymorphism could modify the pglyRp1 functions because the mutated residue is located in a domain that is important for the binding of other molecules.

Objective:: Kappa-casein (CSN3) variant B is a widely known marker of milk processing traits. Betacasein (CSN2) is a source of the opioid-like peptide β-casomorphins-7 (BCM-7), which is yielded by the successive in vitro gastrointestinal proteolytic digestion of the CSN2 A1 variant but not A2. Epidemiological and animal model studies suggest that BCM-7 may be a potential risk factor in the etiology of some human diseases. Because breeding companies and dairy plants have been encouraged to use CSN3 BB bulls for insemination of cows for over 30 yr, it was hypothesized that bulls of CSN3 BB genotype are spreading the undesirable A1 allele of CSN2 in the population of Holstein bulls. Materials and Methods:: Among 519 Holstein bulls, 109 bulls were selected as having the CSN3 BB genotype. These bulls were then genotyped for the CSN2 polymorphism. All bulls had an official breeding index PF (production and functionality). Results and Discussion:: The frequency of undesirable allele A1 of CSN2 locus was relatively high at 31.7%. Among 109 bulls with the CSN3 BB genotype, although 50 bulls had the desirable CSN2 A2A2 genotype, 10 carried the undesirable CSN2 A1A1 genotype. These 10 bulls (CSN3 BB and CSN2 A1A1) had the lowest average PF breeding index. Implications or Applications:: Bulls with CSN3 BB genotype and the CSN2 A2 variant should be preferred in breeding schemes because they simultaneously improve general breeding value and cheese-making properties and promote milk without negative implications on human health.

Objective:: Kappa-casein (CSN3) variant B is a widely known marker of milk processing traits. Betacasein (CSN2) is a source of the opioid-like peptide β-casomorphins-7 (BCM-7), which is yielded by the successive in vitro gastrointestinal proteolytic digestion of the CSN2 A1 variant but not A2. Epidemiological and animal model studies suggest that BCM-7 may be a potential risk factor in the etiology of some human diseases. Because breeding companies and dairy plants have been encouraged to use CSN3 BB bulls for insemination of cows for over 30 yr, it was hypothesized that bulls of CSN3 BB genotype are spreading the undesirable A1 allele of CSN2 in the population of Holstein bulls. Materials and Methods:: Among 519 Holstein bulls, 109 bulls were selected as having the CSN3 BB genotype. These bulls were then genotyped for the CSN2 polymorphism. All bulls had an official breeding index PF (production and functionality). Results and Discussion:: The frequency of undesirable allele A1 of CSN2 locus was relatively high at 31.7%. Among 109 bulls with the CSN3 BB genotype, although 50 bulls had the desirable CSN2 A2A2 genotype, 10 carried the undesirable CSN2 A1A1 genotype. These 10 bulls (CSN3 BB and CSN2 A1A1) had the lowest average PF breeding index. Implications or Applications:: Bulls with CSN3 BB genotype and the CSN2 A2 variant should be preferred in breeding schemes because they simultaneously improve general breeding value and cheese-making properties and promote milk without negative implications on human health.

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Beta-casein A1 protein variant might be one of the risk factors in the etiology of human disorders like diabetes and ischemic heart disease. However, from the practical perspective selecting for the A2 allele in dairy cattle requires knowledge of whether the A1/A2 polymorphism is associated with breeding values for production traits. A DNA fragment containing A1/A2 polymorphic region was amplified and genotyped using the PCR-ACRS (Amplification Created Restriction Site) technique in 478 Holstein-Friesian bulls yielding the allele frequencies of 0.35 and 0.65 for the A1 and the A2 variants, respectively. A linear regression model was used for testing the association between the polymorphism and breeding values for production traits and showed that the allele coding the A2 protein variant increases breeding values for milk and protein yield and decreases breeding values for fat percentage in milk. Genotyping A.I. bulls at beta-casein locus and preferring A2 allele may lead to two benefits: increasing breeding value for protein yield and decreasing frequency of A1 protein variant, being considered as risk factor for human health.

Besides its nutritional value, bovine beta-casein is a source of bioactive peptides called betacasomorphins produced during digestion of raw or processed milk. It was shown that the betacasomorphin 7 originates only from beta-casein variants A1 or B and may be a significant risk factor in human ischemic heart disease, arteriosclerosis, type I diabetes and sudden infant death syndrome. In this study, the frequency of the A1 allele in a sample of Polish Holstein bulls commonly used in artificial insemination (A. I. bulls) was analysed and the potential for production of milk capable of releasing undesirable beta-casomorphin 7 is discussed. Among 143 A. I. bulls, three genotypes were identified (A1/A1, A2/A2, A1/A2) resulting in frequencies of 0.402 and 0.598, for A1 and A2, respectively. Although, the clinical implications of A1 milk on human health is still under discussion it may be necessary to monitor reproductive bulls and decrease the frequency of allele A1.

La mayor parte de la superficie de la region central deArgentina se halla cubierta por vegetacion natural y el manejo al que han sido sometidas hasta la actualidad las ha transformado en areas de baja produccion y dificil manejo. El pastoreo por ganado domestico y los incendios han contribuido al deterioro de estos ecosistemas, que en la actualidad presentan una fuerte invasion de lenosas y pajonal. Una tecnica propuesta ha sido el rolado selectivo que aplasta y fragmenta la vegetacion lenosa e incrementa el area de pastizales. El objetivo de este trabajo es evaluar los efectos del rolado sobre la vegetacion y la retencion de agua en el suelo en un area de renoval y transferir los resultados alcanzados sobre el control las lenosas y la conservacion del suelo con la finalidad de recuperar estas areas degradadas. En un area cubierta de fachinal se realizo un rolado selectivo y se establecieron 2 tratamientos: rolado y testigo. Cada tratamiento tuvo tres repeticiones (transectas) sobre...

En este estudio, 58868 polimorfismos de nucleotido simple (SNPs) obtenidos de poblaciones del banco de germoplasma del ganado Criollo Colombiano Blanco Orejinegro-BON y 57482 del Sanmartinero-SM, fueron utilizados para estimar la heredabilidad de los indices de adaptabilidad, Coeficiente de Adaptabilidad-CA y el Coeficiente de Tolerancia al Calor-HTC y de las caracteristicas reproductivas Edad al primer Parto-EPP e Intervalo Entre Partos-IEP, para realizar estudios de asociacion genomica-GWAS para estas mismas caracteristicas y determinar huellas de seleccion, genes y rutas metabolicas para caracteristicas productivas y de adaptacion. Los componentes de varianza y las heredabilidades se estimaron utilizando el programa AIREMLF90 (Average Information Restricted Maximum Likelihood Fortran90) contenido en la familia de programas BLUPF90 (Best Linear Unbiased Predictor Fortran90). Las heredabilidades en la raza BON para el CA fue de 0.06, HTC de 0.16, EPP de 0.07 e IEP de 0.14. Para la ...

La mayor parte de la superficie de la region central deArgentina se halla cubierta por vegetacion natural y el manejo al que han sido sometidas hasta la actualidad las ha transformado en areas de baja produccion y dificil manejo. El pastoreo por ganado domestico y los incendios han contribuido al deterioro de estos ecosistemas, que en la actualidad presentan una fuerte invasion de lenosas y pajonal. Una tecnica propuesta ha sido el rolado selectivo que aplasta y fragmenta la vegetacion lenosa e incrementa el area de pastizales. El objetivo de este trabajo es evaluar los efectos del rolado sobre la vegetacion y la retencion de agua en el suelo en un area de renoval y transferir los resultados alcanzados sobre el control las lenosas y la conservacion del suelo con la finalidad de recuperar estas areas degradadas. En un area cubierta de fachinal se realizo un rolado selectivo y se establecieron 2 tratamientos: rolado y testigo. Cada tratamiento tuvo tres repeticiones (transectas) sobre...

O objetivo deste trabalho foi identificar o modelo com melhor ajuste aos dados de produção de leite, gordura, proteína e sólidos totais para cabras leiteiras, bem como associar polimorfismos de nucleotídeo único (SNPs) nos genes para κ-caseína (κ-CSN3) e β-lactoglobulina (β-LG) aos parâmetros das curvas de produção e qualidade do leite. Foram avaliados 4.160 registros de produção de leite, gordura, proteína e sólidos totais de cabras das raças Alpina, Saanen e mestiça, no Estado de Antioquia, na Colômbia. Os modelos não lineares com melhor ajuste à estrutura dos dados foram os de Nelder, para produção de leite, e de Cappio-Borlino, para qualidade do leite. As análises de associação mostraram efeito significativo do SNP κ-CSN3 sobre o pico de produção, a produção inicial e a persistência das características qualitativas do leite. Já o SNP β-LG apresentou efeito significativo sobre os picos de produção de leite e gordura, e sobre o tempo necessário para atingir o pico de produção de p...

Kefir is a fermented dairy product, associated to health benefits because of being a probiotic and due to the presence of molecules with biological activity. In this work, we have profiled the peptide composition of goat milk kefir at three different fermentation times using a peptidomics approach, in order to study changes in peptide concentrations and patterns of protein digestion throughout the fermentation time. We identified 2328 unique peptides corresponding to 22 protein annotations, with a maximum of peptides found after 24 h fermentation. We established different digestion patterns according to the nature of the proteins, and quantified the changes in the peptides appearing in all the fermentation times. We also identified 11 peptides that matched exactly to sequences with biological activity in databases, almost all of them belonging to caseins. This is the most comprehensive proteomic analysis of goat milk kefir to date. Highlights  A comprehensive peptidomic analysis of goat milk kefir at different fermentation times.  Establishment of protein digestion patterns throughout the milk fermentation.  Quantification of occurring peptides along the fermentation process.  Identification of peptides with potential biological activity in goat milk kefir.

Milk is an essential food for humans and one of the reasons of its importance lies in the content of milk proteins. The most frequent
proteins in this precious liquid are caseins (αS1-casein, αS2-casein,
β-casein and κ-casein), which are a source of amino acids for the
diet of mammals in their first days of life. In milk, caseins are made
up of molecular aggregates of proteins of varying sizes called
micelles. The objective of this review is to present an overview of
the structure, properties and genetics of dairy caseins and their
relation with human health. From this review, it was established
that αs1 and αs2 caseins are found together with β-casein, forming
the micellar nucleus and interacting with calcium ions, to form and
maintain stable the micelle. Animals genetically characterized
with some variants of these proteins are associated with a yield in
milk volume. For its part, κ-casein is associated with an increase in
the yield and quality of cheeses, hence its economic importance,
while the most common forms of β-casein in dairy cattle are A1
and A2. β-casein A2 does not have negative effects on human
health; on the contrary, it has been associated with lowering properties of cholesterol and triacylglycerides. However, the A1 variant of β-casein produces a bioactive peptide called β-casomorphin-7 (BCM-7), which may play an unclear etiological role in the development of some diseases in humans, such as: ischemic heart disease, type 1 diabetes mellitus, sudden infant death syndrome (SIDS), neurological disorders, such as autism and schizophrenia.

Background: When human milk is unavailable, banked milk is recommended for feeding premature infants. Milk banks use processes to eliminate pathogens; however, variability among methods exists. Research aim: The aim of this study was to compare the macronutrient (protein, carbohydrate, fat, energy), immune-protective protein, and human milk oligosaccharide (HMO) content of human milk from three independent milk banks that use pasteurization (Holder vs. vat techniques) or retort sterilization. Methods: Randomly acquired human milk samples from three different milk banks ( n = 3 from each bank) were analyzed for macronutrient concentrations using a Fourier transform mid-infrared spectroscopy human milk analyzer. The concentrations of IgA, IgM, IgG, lactoferrin, lysozyme, α-lactalbumin, α antitrypsin, casein, and HMO were analyzed by mass spectrometry. Results: The concentrations of protein and fat were significantly ( p < .05) less in the retort sterilized compared with the Holder ...

Taquchi design and Mini-fermentation system was used to optimize the kefir grain production. The effects of different parameters including percentage of fat in milk, skim milk proportion, incubation temperature, incubation time, tryptose, glucose, CO concentration and amount of milk on the percentage yield 2 of kefir grain were investigated. Skim milk and low fat milk were the best medium for kefir grain production. Results of Taguchi design L-18 showed that the effects of percentage and volume of skim milk were 46 and 24%, respectively. Effect of temperature (37°C) was only 5.9% and although fat inhibits kefir grain production but its effect is only 1.8%. It was concluded that the Taguchi design is a promising approach to analysis effect of multi variables simultaneously and economically.

The microorganisms that make up kefir grains are well known for lactose fermentation, but the extent to which they hydrolyze and consume milk proteins remains poorly understood. Peptidomics technologies were used to examine the proteolytic activity of kefir grains on bovine milk proteins. Methods and results: Gel electrophoresis revealed substantial digestion of milk proteins by kefir grains, with mass spectrometric analysis showing the release of 609 protein fragments and alteration of the abundance of >1,500 peptides that derived from 27 milk proteins. Kefir contained 25 peptides identified from the literature as having biological activity, including those with antihypertensive, antimicrobial, immunomodulatory, opioid and anti-oxidative functions. 16S rRNA and shotgun metagenomic sequencing identified the principle taxa in the culture as Lactobacillus species. Conclusion: The model kefir sample contained thousands of protein fragments released in part by kefir microorganisms and in part by native milk proteases.

An extensive mass spectrometry analysis of the human milk peptidome has revealed almost 700 endogenous peptides from 30 different proteins. Two in-house computational tools were created and used to visualize and interpret the data through both alignment of the peptide quasi-molecular ion intensities and estimation of the differential enzyme participation. These results reveal that the endogenous proteolytic activity in the mammary gland is remarkably specific and well conserved. Certain proteins-not necessarily the most abundant ones-are digested by the proteases present in milk, yielding endogenous peptides from selected regions. Our results strongly suggest that factors such as the presence of specific proteases, the position and concentration of cleavage sites, and, more important, the intrinsic disorder of segments of the protein drive this proteolytic specificity in the mammary gland. As a consequence of this selective hydrolysis, proteins that typically need to be cleaved at s...

Taquchi design and Mini-fermentation system was used to optimize the kefir grain production. The effects of different parameters including percentage of fat in milk, skim milk proportion, incubation temperature, incubation time, tryptose, glucose, CO concentration and amount of milk on the percentage yield 2 of kefir grain were investigated. Skim milk and low fat milk were the best medium for kefir grain production. Results of Taguchi design L-18 showed that the effects of percentage and volume of skim milk were 46 and 24%, respectively. Effect of temperature (37°C) was only 5.9% and although fat inhibits kefir grain production but its effect is only 1.8%. It was concluded that the Taguchi design is a promising approach to analysis effect of multi variables simultaneously and economically.