Sedimentation Analysis of Bovine Milk Casein Micelle at pH 6.8 and pH 5.8

Although widely adopted by the chemical and pharmaceutical industries in recent years, little published data is available regarding possible applications of high pressure homogenisation for dairy products. The objective of this work was to compare the effects of conventional (18 MPa, two-stage) and single or two-stage high pressure homogenisation (HPH) at 50–200 MPa on some properties of raw whole bovine milk (∼4% fat). Fat globule size decreased as HPH pressure increased and, under certain conditions of temperature and pressure, HPH yielded significantly smaller fat globules than conventional homogenisation. Fat globule size was also affected by milk inlet temperature. The pH of all homogenised milk samples decreased during 24 h refrigerated storage. Total bacterial counts of milk were decreased significantly (P<0·05) for milk samples HPH-treated at 150 or 200 MPa. Whiteness and rennet coagulation properties of milk were unaffected or enhanced, respectively, as homogenisation pressure was increased. Average casein micelle size decreased slightly when skim milk was homogenised at 200 MPa. Thus, HPH treatment has several, potentially significant, effects on milk properties.

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Inhibition of proliferative responses of mouse spleen lymphocytes and rabbit Peyer's patch cells by bovine milk caseins and their digests

Journal of Dairy Research ◽

10.1017/s0022029900031034 ◽

1995 ◽

Vol 62 (2) ◽

pp. 339-348 ◽

Cited By ~ 69

Author(s):

Hajime Otani ◽

Isao Hata

Keyword(s):

Colorimetric Assay ◽

Bovine Milk ◽

Inhibitory Effect ◽

Mouse Spleen ◽

Pokeweed Mitogen ◽

Peyer’S Patch ◽

Peyer's Patch ◽

Diphenyltetrazolium Bromide ◽

Spleen Lymphocytes ◽

Milk Casein

SUMMARYThe modulating effect of bovine milk casein components and their digests on the proliferative responses of mouse spleen lymphocytes and rabbit Peyer's patch cells induced or not induced by mitogens has been studied with a colorimetric assay using 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. All the casein components and their digests tested had little mitogenic effect on the proliferative responses of mouse spleen lymphocytes and rabbit Peyer's patch cells. Intact κ-casein significantly inhibited the proliferative responses of mouse spleen lymphocytes and Peyer's patch cells induced by mitogens such as lipopolysaccharide fromSalmonella typhimurium, concanavalin A, phytohaemagglutinin and pokeweed mitogen. In contrast, intact αsl-casein and β-casein had little effect. κ-Casein had an inhibitory effect after digesti on by pancreatin or trypsin, but not after pepsin or chymotrypsin digestion. Both pancreatin and trypsin digests of αsl-casein and -casein significantly inhibited the proliferative responses of mouse spleen lymphocytes and rabbit Peyer's patch cells induced by mitogens, whereas pepsin and chymotrypsin digests of both caseins were without effect. Moreover, the trypsin digest of each casein component had an inhibitory effect on mouse spleen lymphocyte proliferation in the absence of mitogen. Since trypsin is a major proteinase in pancreatin, the substrate specificity of trypsin seems to be important for the formation of the inhibitory peptides from casein components. These observations suggest that intact κ-casein and some peptides formed from milk casein components by the action of trypsin may suppress the immune responsiveness of neonates.

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Effect of temperature on casein micelle composition and gelation of bovine milk

International Dairy Journal ◽

10.1016/j.idairyj.2017.10.008 ◽

2018 ◽

Vol 78 ◽

pp. 20-27 ◽

Cited By ~ 7

Author(s):

Yuan Zhang ◽

Dasong Liu ◽

Xiaoming Liu ◽

Feng Hang ◽

Peng Zhou ◽

...

Keyword(s):

Bovine Milk ◽

Effect Of Temperature ◽

Casein Micelle

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Inelastic light-scattering study of the size distribution of bovine milk casein micelles

Biochemistry ◽

10.1021/bi00801a029 ◽

1971 ◽

Vol 10 (25) ◽

pp. 4788-4793 ◽

Cited By ~ 61

Author(s):

S. H. C. Lin ◽

R. K. Dewan ◽

V. A. Bloomfield ◽

C. V. Morr

Keyword(s):

Light Scattering ◽

Size Distribution ◽

Bovine Milk ◽

Casein Micelles ◽

Inelastic Light Scattering ◽

Scattering Study ◽

Milk Casein

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Tissue-type plasminogen activator and plasminogen embedded in casein rule its degradation under physiological situations: manipulation with casein hydrolysate

Journal of Dairy Research ◽

10.1017/s0022029913000010 ◽

2013 ◽

Vol 80 (2) ◽

pp. 227-232 ◽

Cited By ~ 10

Author(s):

Nissim Silanikove ◽

Fira Shapiro ◽

Uzi Merin ◽

Gabriel Leitner

Keyword(s):

Plasminogen Activator ◽

Bovine Milk ◽

Casein Hydrolysate ◽

Tissue Type ◽

Casein Micelle ◽

Tissue Type Plasminogen Activator ◽

Type Plasminogen Activator ◽

Functional Complex ◽

Mammary Gland Epithelial Cells ◽

Hydrolysis Of

The aims of this study were to test the assumption that tissue-type plasminogen activator (t-PA) and plasminogen (PG) are closely associated with the casein micelle and form a functional complex that rules casein degradation. This assumption was essentially verified for bovine milk under conditions wherein the plasmin system was activated by treatment with casein hydrolysate. It was also shown that urokinase-type PA (u-PA), the second type of plasminogen activator present in milk, was not involved in casein degradation. In agreement with previous studies, we show that treatment with casein hydrolysate precipitously reduced mammary secretion, disrupted the tight junction integrity (increase in Na+ and decrease in K+ concentrations), induced hydrolysis of casein, and activated various elements of the innate and acquired immune system. In the present study, we have identified t-PA as the principal PA, which is responsible for the conversion of PG to plasmin. It was found that t-PA and plasminogen are present in freshly secreted milk (less than 10 min from its secretion), suggesting that they are secreted as a complex by the mammary gland epithelial cells. Further research is needed to provide the direct evidence to verify this concept.

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Influence of homogenization of concentrated milks on the structure and properties of rennet curds

Journal of Dairy Research ◽

10.1017/s0022029900023177 ◽

1983 ◽

Vol 50 (3) ◽

pp. 341-348 ◽

Cited By ~ 70

Author(s):

Margaret L. Green ◽

Richard J. Marshall ◽

Frank A. Glover

Keyword(s):

Fatty Acid ◽

Free Fatty Acid ◽

Size Distribution ◽

Casein Micelle ◽

Structure And Properties ◽

Moisture Retention ◽

Casein Micelles ◽

Micelle Size ◽

Whole Milk ◽

Milk Casein

SummaryWhole milk was concentrated by ultrafiltration in a plant causing some homogenization of the fat. Comparisons were made with milk concentrated in a plant causing little homogenization and with milk homogenized conventionally. None of the processes appreciably affected the casein micelle size distribution. On rennet treatment of homogenized milk, casein micelle aggregation occurred more slowly, the protein network in the curd was less coarse and the rate of whey loss was reduced, compared with non-homogenized milk at the same concentration. In using concentrated milks for cheesemaking homogenization improved the composition of Cheddar cheese, because of increased fat and moisture retention, but curd fusion was poorer. Some aspects of the texture of the mature cheeses were improved, but the free fatty acid levels were higher. Values for the firmness of curds, formed from milks processed in different ways, did not relate to the extent of aggregation of the casein micelles. It is suggested that the complete cheesemaking process is driven by the tendency of the casein to aggregate.

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High-pressure treatment of milk: effects on casein micelle structure and on enzymic coagulation

Journal of Dairy Research ◽

10.1017/s0022029999004021 ◽

2000 ◽

Vol 67 (1) ◽

pp. 31-42 ◽

Cited By ~ 130

Author(s):

ERIC C. NEEDS ◽

ROBERT A. STENNING ◽

ALISON L. GILL ◽

VICTORIA FERRAGUT ◽

GILLIAN T. RICH

Keyword(s):

Whey Proteins ◽

Skim Milk ◽

Casein Micelle ◽

Casein Micelles ◽

Dense Networks ◽

Protein Levels ◽

Micelle Structure ◽

Milk Casein ◽

Β Lactoglobulin ◽

Gel Network

High isostatic pressures up to 600 MPa were applied to samples of skim milk before addition of rennet and preparation of cheese curds. Electron microscopy revealed the structure of rennet gels produced from pressure-treated milks. These contained dense networks of fine strands, which were continuous over much bigger distances than in gels produced from untreated milk, where the strands were coarser with large interstitial spaces. Alterations in gel network structure gave rise to differences in rheology with much higher values for the storage moduli in the pressure-treated milk gels. The rate of gel formation and the water retention within the gel matrix were also affected by the processing of the milk. Casein micelles were disrupted by pressure and disruption appeared to be complete at treatments of 400 MPa and above. Whey proteins, particularly β-lactoglobulin, were progressively denatured as increasing pressure was applied, and the denatured β-lactoglobulin was incorporated into the rennet gels. Pressure-treated micelles were coagulated rapidly by rennet, but the presence of denatured β-lactoglobulin interfered with the secondary aggregation phase and reduced the overall rate of coagulation. Syneresis from the curds was significantly reduced following treatment of the milk at 600 MPa, probably owing to the effects of a finer gel network and increased inclusion of whey protein. Levels of syneresis were more similar to control samples when the milk was treated at 400 MPa or less.

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Distribution of plasminogen activator in different fractions of bovine milk

Journal of Dairy Research ◽

10.1017/s0022029900033720 ◽

1995 ◽

Vol 62 (1) ◽

pp. 115-122 ◽

Cited By ~ 30

Author(s):

Jeffrey H. White ◽

Boris Zavizion ◽

Kristen O'Hare ◽

James Gilmore ◽

Ming R. Guo ◽

...

Keyword(s):

Plasminogen Activator ◽

Somatic Cells ◽

Bovine Milk ◽

Skim Milk ◽

Raw Milk ◽

Sds Page ◽

Predominant Form ◽

Cell Pellet ◽

Molecular Masses ◽

Milk Casein

SUMMARYThe type and relative amounts of plasminogen activator (PA) in different fractions of bovine milk obtained from 15 Holstein cows were examined. Raw milk was centrifuged to separate skim milk and a somatic cell pellet. PA was mainly localized within the casein fraction, being 42 times that in the serum, and in association with somatic cells. The predominant form of PA in milk casein was isolated from SDS-PAGE gel extracts and had a molecular mass of ∽75 kDa. Its activity was increased 41-fold (P < 0·01) in the presence of fibrin but was unaffected by the presence of amiloride, indicating that it was due to tissue-PA. The predominant forms of PA associated with milk somatic cells were isolated from SDS-PAGE gel extracts and had molecular masses of ∽ 30 and ∽ 50 kDa. The activity of both proteins was unaffected by the presence of fibrin but was dramatically reduced by the presence of amiloride, indicating that they represented urokinase-PA.

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