Stability of buffalo casein micelles

1979 ◽  
Vol 46 (2) ◽  
pp. 401-405 ◽  
Author(s):  
Nripendra C. Ganguli
Keyword(s):  
Sialic Acid ◽  
Gel Filtration ◽  
Skim Milk ◽  
Heat Stability ◽  
Casein Micelles ◽  
Heat Stable ◽  
Micellar Casein ◽  
Acid Release ◽  
The Stability ◽  
Better Than

SUMMARYBuffalo skim-milk is less heat stable than cow skim-milk. Interchanging ultracentrifugal whey (UCW) and milk diffusate with micellar casein caused significant changes in the heat stability of buffalo casein micelles (BCM) and cow casein micelles (CCM). Buffalo UCW dramatically destabilized COM, whereas buffalo diffu-sate with CCM exhibited the highest heat stability.Cow κ-casein stabilizes αs-casein against precipitation by Ca better than buffalo º-casein. About 90% of αs-casein could be stabilized by κ: αs ratios of 0·20 and 0·231 for cow and buffalo, respectively.Sialic acid release from micellar κ-casein by rennet was higher than from acid κ-casein in both buffalo and cow caseins, the release being slower in buffalo. The released macropeptide from buffalo κ-casein was smaller than that from cow κ-casein as revealed by Sephadex gel filtration.Sub-units of BCM have less sialic acid (1·57mg/g) than whole micelles (2·70mg/g). On rennet action, 47% of bound sialic acid was released from sub-units as against 85% from whole micelles. The sub-micelles are less heat stable than whole micelles. Among ions tested, added Ca reduced heat stability more dramatically in whole micelles, whereas added phosphate improved the stability of micelles and, more strikingly, of sub-micelles. Citrate also improved the heat stability of sub-micelles but not of whole micelles.

Separation of the submicelles from micellar casein by high performance gel chromatography on a TSK-GEL G4000SW column

1983 ◽  
Vol 50 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Tomotada Ono ◽  
Satoshi Odagiri ◽  
Toshio Takagi
Keyword(s):  
High Performance ◽  
Skim Milk ◽  
Gel Chromatography ◽  
Casein Micelles ◽  
The Third ◽  
Micellar Casein ◽  
Better Than

SummaryBovine caseins from skim-milk (micellar casein and acid precipitated casein) were separated into 4 discrete components by high performance gel chromatography on a TSK-GEL G4000SW columm. The resolution was better than that obtained by conventional gel chromatography which resulted in separation into 2 components at best. Our results showed that the second and third components consisted of αs1- and κ-caseins and αs1- and β-caseins respectively. They are presumed to be submicellar fractions. Samples prepared by removal of Ca phosphate from large and small micelles were rich in the third and the second components respectively. It is suggested that casein micelles consist of αs1- and κ-casein complexes and complexes and polymers of αs1- and β-casein which are situated preferentially on the periphery and in the interior of the micelles respectively.

Modelling of heat stability and heat-induced aggregation of casein micelles in concentrated skim milk using a Weibullian model

2018 ◽  
Vol 71 (3) ◽  
pp. 601-612 ◽  
Author(s):  
Joseph Dumpler ◽  
Felicitas Peraus ◽  
Verena Depping ◽  
Bryndís Stefánsdóttir ◽  
Martin Grunow ◽  
...  
Keyword(s):  
Skim Milk ◽  
Heat Stability ◽  
Casein Micelles ◽  
Induced Aggregation

Ethanol stability of casein micelles – a hypothesis concerning the role of calcium phosphate

1987 ◽  
Vol 54 (3) ◽  
pp. 389-395 ◽  
Author(s):  
David S. Horne
Keyword(s):  
Ionic Strength ◽  
Skim Milk ◽  
Buffer System ◽  
Casein Micelles ◽  
Buffer Solutions ◽  
Relative Response ◽  
Using Data ◽  
The Stability ◽  
Ethanol Stability

SummaryThe ethanol (EtOH) stability of skim milk and the stability towards aggregation of casein micelles diluted into ethanolic buffer solutions were compared using data obtained from previously published experiments. Differences in absolute stability and in relative response were observed when Ca2+ level and pH were adjusted, the buffer system results lying below those from skim milk in both cases. Increasing the ionic strength of skim milk adjusted to pH 7·0 lowered its EtOH stability whereas increasing the ionic strength of the diluting buffer increased the stability of the casein micelles. The hypothesis is put forward that the differences are due to the simultaneous precipitation of Ca phosphate when EtOH is added to skim milk. This draws calcium from the caseinate sites of the micelle, counteracting the destabilizing effects of the EtOH towards the micelle. Such removal and the consequent restructuring are kinetically controlled and micellar precipitation in skim milk finally occurs when the micellar coagulation time falls within the time scale of the restructuring reactions.

scholarly journals Preliminary characterization of a heat-stable protein from rat adipose tissue whose phosphorylation is stimulated by insulin

1982 ◽  
Vol 204 (3) ◽  
pp. 817-824 ◽  
Author(s):  
P J Blackshear ◽  
R A Nemenoff ◽  
J Avruch
Keyword(s):  
Adipose Tissue ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Gel Filtration ◽  
Heat Stability ◽  
Intact Cells ◽  
Heat Stable ◽  
Heat Stable Protein ◽  
Rat Adipose Tissue

Exposure of 32P-labelled isolated rat adipocytes or epididymal fat-pads to insulin resulted in an increase in the phosphorylation of a heat-stable acid-soluble protein of Mr 22 000. The phosphorylation of this protein was unaffected by isoprenaline (isoproterenol) in intact cells, nor was its phosphorylation catalysed by exposure in vitro to the cyclic AMP-dependent protein kinase or smooth-muscle myosin light-chain kinase. The properties of the Mr-22 000 protein include: heat-stability; solubility in 1% trichloroacetic acid; pI 4.9; elution at apparent Mr 37 500 on gel filtration; and it contains both phosphoserine and phosphothreonine. It can be distinguished from the heat-stable phosphatase inhibitor 1 of adipose tissue (inhibitor 1A) and the phosphorylated form of adipose-tissue myosin light chain by several criteria. Its identity, and the possible functional significance of the insulin-stimulated phosphorylation, remain problems for future study.

Effect of urea on the heat coagulation of the caseinate complex in skim-milk

1977 ◽  
Vol 44 (2) ◽  
pp. 249-257 ◽  
Author(s):  
D. D. Muir ◽  
A. W. M. Sweetsur
Keyword(s):  
Activation Energy ◽  
Skim Milk ◽  
Heat Stability ◽  
Coagulation Time ◽  
Temperature Range ◽  
The Stability

SummaryAdditions of urea progressively increased the heat stability of milk outside of its coagulation time (CT)–pH minimum. In the region of the CT–pH minimum larger amounts of urea were required before an increase in heat stability occurred. The effect of urea was observed over the temperature range 125–140 °Cfornaturalmilk, milk which had been dialysed against synthetic sera, and milk to which a sulphydrylblocking agent had been added. Urea additions did not affect the activation energy of the heat coagulation reaction or the stability of milk to rennet or ethanol.

A study of the properties of dissociated bovine casein micelles

1975 ◽  
Vol 42 (1) ◽  
pp. 169-183 ◽  
Author(s):  
L. K. Creamer ◽  
Gillian P. Berry
Keyword(s):  
Electron Microscopy ◽  
Ionic Strength ◽  
Gel Filtration ◽  
Protein Composition ◽  
Leading Edge ◽  
Urea Solution ◽  
Casein Micelle ◽  
Casein Micelles ◽  
Micellar Casein ◽  
Sepharose 4B

SummaryAlthough casein micelles are disrupted by removal of Ca, individual caseins remain aggregated in sub-micellar casein aggregates or sub-units. These sub-units have been studied by: (1) the use of gel filtration on Sepharose 4B at 6, 20 and 37°C at pH 6·7 and 0·1 ionic strength, (2) ultracentrifugation and (3) electron microscopy. At 37°C the protein composition of the sub-units varied across the gel-filtration peak, with κ-casein being eluted towards the leading edge and the ratio of αs1- to β-casein being almost constant across the peak. Re-chromatography of the protein from the leading edge of this peak gave a new wide peak with the κ-casein again being eluted towards the leading edge. However, αs1-casein was eluted before β-casein in the leading edge of the new peak. Prior treatment of the casein micelles by dispersion with 6 m-urea solution, precipitation with acid or reduction with 2-mercaptoethanol did not alter the gel-filtration pattern. An examination of the purified casein components and their mixtures showed that a 1:1 ratio mixture of αs1- and β-casein had the same peak maximum elution volume as casein micelle sub-units. κ-Casein by itself eluted at the void volume of the gel-filtration column, but after admixture with a sample of small micelles it eluted at the leading edge of the sub-unit peak and was indistinguishable from the κ-casein normally present. These results suggest that the sub-units are in equilibrium with their component caseins and that their size distribution is determined by only those factors (such as protein concentration, pH, temperature and ionic strength) which determine the strength of association between the casein components. The results from electron microscopy and ultracentrifugation support these conclusions.

Heat stability of milk: further studies on the pH-dependent dissociation of micellar κ-casein

1986 ◽  
Vol 53 (2) ◽  
pp. 237-248 ◽  
Author(s):  
Harjinder Singh ◽  
Patrick F. Fox
Keyword(s):  
Whey Protein ◽  
Cetyltrimethylammonium Bromide ◽  
Opposite Effect ◽  
Whey Proteins ◽  
Sodium Dodecyl ◽  
Skim Milk ◽  
Heat Stability ◽  
Casein Micelles ◽  
Acetylneuraminic Acid ◽  
Ph Dependent

SUMMARYWhey protein complexed and became co-sedimentable with casein micelles after heating milk at ≥ 90°C for 10 min at pH ≤ 6·9 while at higher pH values (7·3) whey proteins and κ-casein-rich protein dissociated from the micelles on heating. κ-Casein-deficient micelles were more sensitive to heat, Ca2+ or ethanol than whey protein-coated or native micelles and were readily coagulable by rennet. Isolated κ-casein added to skim milk before preheating (90°C for 10 min) did not associate with the micelles at pH ≥ 6·9. Sodium dodecyl sulphate increased the level of both non-sedimentable N (NSN) and N-acetylneuraminic acid (NANA) and shifted the NSN-pH and NANA-pH curves to more acidic values while cetyltrimethylammonium bromide had the opposite effect. It is suggested that the pH-dependent dissociation in micellar κ-casein, which appears to be reversible, depends on the surface charge on the micelles; at a certain negative charge, disruption of hydrophobic and electrostatic forces could result in the dissociation of κ-casein from the casein micelles.

Effects of added salts on the heat stability of recombined concentrated milk

1990 ◽  
Vol 57 (2) ◽  
pp. 213-226 ◽  
Author(s):  
Mary-Ann Augustin ◽  
Phillip T. Clarke
Keyword(s):  
Skim Milk ◽  
Heat Stability ◽  
Ph Control ◽  
Ph Profile ◽  
Heat Stable ◽  
Low Levels ◽  
Concentrated Milk ◽  
Milk Solids ◽  
Ph Curve

SummaryChanges in heat stability and Ca2+ activity of recombined concentrated milk (18% solids non-fat:8% fat) induced by the additions of 0·011–0·217 mol phosphate/kg skim milk solids (SMS), 0·022–0·217 mol citrate/kg SMS, 0·011–0·022 mol Ca/kg SMS and 0·016–0·067 mol EDTA/kg SMS were evaluated. Heat stability was assessed using an objective method which involved determination of viscosity after heating under controlled conditions. Low levels of added phosphate and citrate generally effected an acid shift of the viscosity–pH profile, while higher levels caused a broadening of the profile. Addition of CaCl2 at a level of 0·011 mol/kg SMS resulted in a narrowing of the viscosity–pH curve; additions of higher levels resulted in a non-heat stable recombined milk concentrate. EDTA also caused a narrowing of the viscosity–pH curve. The results highlight the importance of pH control for effective stabilization of recombined milk concentrates by additions of phosphate and citrate.

Differences between the Sugar Moieties of Liver- and Bone-Type Alkaline Phosphatases: A Re-Evaluation

1994 ◽  
Vol 31 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Masakazu Miura ◽  
Yoshikatsu Sakagishi ◽  
Keishi Hata ◽  
Tsugikazu Komoda
Keyword(s):  
Sialic Acid ◽  
Heat Exposure ◽  
Molecular Size ◽  
Heat Stability ◽  
Additional Treatment ◽  
Alkaline Phosphatases ◽  
Sugar Moiety ◽  
Heat Stable ◽  
The Difference ◽  
Sialic Acid Linkage

We re-evaluated the differences between the sugar moieties of liver and bone alkaline phosphatases (ALPs). Sialic acid was added to ALP sugar moieties by α2,3- or 2,6-sialyltransferase treatment of the asialo-form ALP (neuraminidase-treated ALP). Asialo-bone ALP was converted to a liver-like ALP by the 2,6-sialyltransferase treatment. The resulting liver-like ALP was less susceptible to neuraminidase than non-treated bone ALP, but was still labile to heat exposure at 56°C like non-treated bone ALP. However, after the O-linked sugar moiety had been released by additional treatment with O-glycanase the liver-like ALP became more heat stable at 56°C, like non-treated liver ALP. Non-treated liver ALP reacted specifically with anti-liver ALP monoclonal antibody, and non-treated bone ALP reacted with both anti-liver and anti-bone ALP antibodies. The asialo-bone ALP still reacted with anti-bone ALP antibody, whereas the asialo-form liver ALP showed little, if any, reaction with anti-liver and anti-bone ALP antibodies. Neuraminidase and O-glycanase-treated bone ALP reacted less with anti-bone ALP antibody. After O-glycanase treatment, bone ALP molecules deprived of an O-linked sugar moiety had a molecular size and heat stability similar to liver ALP. The difference between liver and bone ALP molecules may be due not only to their manner of sialic acid linkage but also to the attachment of the O-linked sugar moiety.

Natural variations in the average size of bovine casein micelles: II. Milk samples from creamery bulk silos in south west Scotland

1978 ◽  
Vol 45 (3) ◽  
pp. 347-353 ◽  
Author(s):  
Carl Holt ◽  
D. Donald Muir
Keyword(s):  
Causal Relation ◽  
Skim Milk ◽  
Heat Stability ◽  
Wavelength Dependence ◽  
Unit Weight ◽  
Winter Period ◽  
Casein Micelles ◽  
South West ◽  
Natural Variations ◽  
Average Size

SummarySamples of bulk silo milk from 5 creameries in the south west of Scotland were taken over a 16-month period. The average radii of casein micelles were determined by measuring the wavelength dependence of the turbidity of skim-milk diluted with its own ultrafiltrate. In addition, the concentrations of casein, soluble and colloidal Ca and P1 were measured. The average size of casein micelles followed a pronounced seasonal trend with smaller average sizes in the summer compared to the winter period, confirming earlier observations made on milks from individual cows. The average size of casein micelles correlated positively (r = +0·777, P < 0·001) with the amount of colloidal P1 per unit weight of casein and negatively (r = −0·77, P < 0·001) with casein-bound Ca. Average micelle radius was negatively correlated with heat stability at the natural pH of milk (r = −0·61, P < 0·001), but there did not appear to be any causal relation between these 2 variables.

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