Addition of sodium caseinate to skim milk inhibits rennet-induced aggregation of casein micelles

SummaryThe susceptibility of the casein in milk to proteolysis was shown to be greatly influenced by its state of aggregation. In normal milk, where the casein is largely in micellar form, the αs1- and β-caseins are almost inaccessible to proteolysis. On removal of the colloidal phosphate, the casein micelles disintegrate, rendering the components, especially the αs1-casein, accessible to proteolysis. The role of colloidal calcium phosphate in the casein micelle is believed to be that of a non-specific aggregating agent which can be effectively replaced by calcium. Dissolved colloidal phosphate can be effectively reformed by elevation of the pH of colloidal phosphate-free (CPF) milk before equilibrium dialysis. Addition of κ-casein to CPF milk also causes aggregation of the component caseins but the micelles formed are smaller than those of normal milk.The behaviour of micellar β-casein differs considerably from that of micellar αs1-casein. The evidence suggests that part of the β-casein freely dissociates either outside or within the micelle when the temperature is reduced. The temperature dependence of the susceptibility of β-casein to proteolysis was similar in skim-milk and in solutions of sodium caseinate, and increased as the temperature was reduced. αs1-Casein was quite resistant to proteolysis in normal milk but became susceptible when the micelle structure was disrupted on removal of colloidal phosphate.It is concluded that limited proteolysis may prove a valuable technique in the study of casein micelle structure.

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Sodium caseinate-stabilized fat globules inhibition of the rennet-induced gelation of casein micelles studied by Diffusing Wave Spectroscopy

Food Hydrocolloids ◽

10.1016/j.foodhyd.2008.07.019 ◽

2009 ◽

Vol 23 (4) ◽

pp. 1134-1138 ◽

Cited By ~ 10

Author(s):

Zafir Gaygadzhiev ◽

Marcela Alexander ◽

Milena Corredig

Keyword(s):

Sodium Caseinate ◽

Diffusing Wave Spectroscopy ◽

Casein Micelles ◽

Fat Globules

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The influence of sodium caseinate and β-casein concentrate on the physicochemical properties of casein micelles and the role of tea polyphenols in mediating these interactions.

LWT ◽

10.1016/j.lwt.2021.112775 ◽

2021 ◽

pp. 112775

Author(s):

Tessa M. van de Langerijt ◽

James A. O'Mahony ◽

Shane V. Crowley

Keyword(s):

Physicochemical Properties ◽

Sodium Caseinate ◽

Tea Polyphenols ◽

Casein Micelles

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

Journal of Dairy Research ◽

10.1017/s0022029900025565 ◽

1987 ◽

Vol 54 (3) ◽

pp. 389-395 ◽

Cited By ~ 15

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.

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Stability of buffalo casein micelles

Journal of Dairy Research ◽

10.1017/s0022029900017404 ◽

1979 ◽

Vol 46 (2) ◽

pp. 401-405 ◽

Cited By ~ 4

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.

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Changes in milk on heating: viscosity measurements

Journal of Dairy Research ◽

10.1017/s0022029900027461 ◽

1993 ◽

Vol 60 (2) ◽

pp. 139-150 ◽

Cited By ~ 87

Author(s):

Theo J. M. Jeurnink ◽

Kees G. De Kruif

Keyword(s):

Heat Treatment ◽

Heat Exchangers ◽

Hard Spheres ◽

Whey Proteins ◽

Skim Milk ◽

Quantitative Model ◽

Casein Micelles ◽

Mutual Attraction ◽

Viscosity Measurements ◽

Quantitative Basis

SummarySkim milk was heated at 85 °C for different holding times. As a result of such heating, whey proteins, in particular β-lactoglobulin, denatured and associated with casein micelles. This led to an increase in size of the casein micelles but also to a different interaction between them. Both these changes could be described by using a quantitative model which was developed for the viscosity of so-called adhesive hard spheres. We applied the model successfully to skim milk and were able to describe on a quantitative basis the changes due to the heat treatment of milk. It was shown that after heating the casein micelles became larger and acquired a mutual attraction. The unfolding of the whey proteins and their subsequent association with the casein micelles appeared to be responsible for these changes. How this reaction influences the fouling of heat exchangers is discussed.

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Changes in Size of Casein Micelles Caused by Growth of Psychrotrophic Bacteria in Raw Skim Milk

Journal of Food Protection ◽

10.4315/0362-028x-47.1.16 ◽

1984 ◽

Vol 47 (1) ◽

pp. 16-19 ◽

Cited By ~ 1

Author(s):

JONATHAN P. BURLINGAME-FREY ◽

ELMER H. MARTH

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Skim Milk ◽

Bacterial Activity ◽

Casein Micelles ◽

Psychrotrophic Bacteria ◽

Ph Values ◽

Psychrotrophic Bacterium ◽

Transmission Electron

Raw skim milk was inoculated (1%, v/v) with a proteolytic psychrotrophic bacterium that previously was isolated from milk. The inoculated skim milk was incubated at 7°C for 0, 3, 5 and 7 d. The pH values for the milk were 6.6, 6.5, 6.45 and 5.95, and the numbers of psychrotrophs/ml were 1.0 × 104 8.9 × 107, 9.0 × 108 and 2.5 × 108 for days 0, 3, 5 and 7, respectively. Samples of milk were negatively stained, examined with transmission electron microscopy and distribution of sizes of casein micelles was determined. The average and (mode) sizes of micelles were 849 (789), 1030 (634), 761 (634) and 405 (316) Angstroms for milks after days 0, 3, 5 and 7, respectively. Another set of samples was prepared from skim milk immediately after it was acidified to pH values of 6.6, 6.5, 6.45 and 5.95. The average and (mode) sizes of micelles were 891 (766), 875 (615), 913 (766) and 840 (615) Angstroms for milks having pH values of 6.6, 6.5, 6.45 and 5.95, respectively. Changes in size of micelles in the incubated samples resulted from bacterial activity other than small changes in pH.

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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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