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Effects of heat treatment and acidification on the dissociation of bovine casein micelles

  • Andrew J. R. Law (a1)


The effects of heat treatment and subsequent acidification of milk on the distribution of proteins, Ca and Pi, between the serum and micellar phases were examined using ultracentrifugation. After heating milk at 85 °C for 10 min, and storing for 22 h at 4, 20 or 30 °C, there was a marked increase in the concentration of κ-casein in the serum. At 4 and 20 °C there was also slightly more β-casein in the serum from heat-treated milk than in that from the corresponding raw milk. The whey proteins were extensively denatured, and were almost equally distributed between the supernatants and micellar pellets. After storage for 22 h the distribution of Ca and Pi between soluble and colloidal phases in heat-treated milk was similar to that in raw milk. After acidifying heat-treated milk by the addition of glucono-δ-lactone and storing for 22 h at 4, 20 or 30 °C there was progressive solubilization of colloidal calcium phosphate with decreasing pH, and at pH 5·0 almost all of the Ca and Pi was present in the serum. At 20 °C, and even more so at 4 °C, serum concentrations of the individual caseins increased considerably with decreasing pH, reaching maximum levels of about 25 and 40% of the total casein at pH 5·7 and 5·5 respectively, and then decreasing rapidly at lower pH. Compared with raw milk, maximum dissociation in heat-treated milks stored at 4 and 20 °C occurred at higher pH, and the overall levels of dissociation of individual caseins from the micelles were lower. At 30 °C, the concentrations of individual caseins in the serum of heat-treated milk decreased steadily as the pH was reduced, and did not show the slight increase found previously for raw milk. The role of the denatured whey proteins in interacting with κ-casein and in promoting aggregation of the micelles on acidification is discussed.



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Ali, A. E., Andrews, A. T. & Cheeseman, G. C. 1980 Influence of storage of milk on casein distribution between the micellar and soluble phases and its relationship to cheese-making parameters. Journal of Dairy Research 47 371382
Aoki, T., Suzuki, H. & Imamura, T. 1974 Formation of soluble casein in whey protein-free milk heated at high temperatures. Milchwissenschaft 29 589594
Chaplin, L. C. 1984 Studies on micellar calcium phosphate: composition and apparent solubility product in milk over a wide pH range. Journal of Dairy Research 51 251257
Connerty, H. V. & Briggs, A. R. 1966 Determination of serum calcium by means of orthocresolphthalein complexonc. American Journal of Clinical Pathology 45 290296
Creamer, L. K., Berry, G. P. & Matheson, A. R. 1978 The effect of pH on protein aggregation in heated skim milk. New Zealand Journal of Dairy Science and Technology 13 915
Creamer, L. K., Berry, G. P. & Mills, O. E. 1977 A study of the dissociation of β-casein from the bovine casein micelle at low temperature. New Zealand Journal of Dairy Science and Technology 12 5866
Dalgleish, D. G. & Law, A. J. R. 1988 pH-Induced dissociation of bovine casein micelles. I. Analysis of liberated caseins. Journal of Dairy Research 55 529538
Dalgleish, D. G. & Law, A. J. R. 1989 pH-lnduced dissociation of bovine casein micelles. II. Mineral solubilization and its relation to casein release. Journal of Dairy Research 56 727735
Davies, D. T. & Law, A. J. R. 1983 Variation in the protein composition of bovine casein micelles and serum casein in relation to micellar size and milk temperature. Journal of Dairy Research 50 6775
Downey, W. K. & Murphy, R. F. 1970 The temperature-dependent dissociation of β-casein from bovine casein micelles and complexes. Journal of Dairy Research 37 361372
Emmons, D. B., Price, W. V. & Swanson, A. M. 1959 Factors affecting the pH of skimmilk coagulation by lactic culture. Journal of Dairy Science 42 589597
Fiske, C. H. & Subbarow, Y. 1925 The colorimetric determination of phosphorus. Journal of Biological Chemistry 66 375400
Griffin, M. C. A., Lyster, R. L. J. & Price, J. C. 1988 The disaggregation of calcium-depleted casein micelles. European Journal of Biochemistry 174 339343
Grigorov, H. 1966 Effect of various types of heat processing of cow's milk on the duration of the coagulation process and on the pH and acidometric titration values of Bulgarian sour milk (yoghurt). Proceedings, 17th International Dairy Congress, München EF 643647
Haque, Z. & Kinsella, J. F. 1988 Interaction between heated κ-casein and β-lactoglobulin: predominance of hydrophobic interactions in the initial stages of complex formation. Journal of Dairy Research 55 6780
Holt, C. 1982 Inorganic constituents of milk. III. The colloidal calcium phosphate of cow's milk. Journal of Dairy Research 49 2938
Holt, C., Davies, D. T. & Law, A. J. R. 1986 Effects of colloidal calcium phosphate content and free calcium ion concentration in the milk serum on the dissociation of bovine casein micelles. Journal of Dairy Research 53 557572
Horne, D. S. & Davidson, C. M. 1993 Influence of heat treatment on gel formation in acidified milks. International Dairy Federation Bulletin Special Issue no. 9303 267–276
Kannan, A. & Jenness, R. 1961 Relation of milk serum proteins and milk salts to the effects of heat, treatment on rennet clotting. Journal of Dairy Science 44 808822
Law, A. J. R., Horse, D. S., Banks, J. M. & Leaver, J. 1994 Heat-induced changes in the whey proteins and caseins. Milchwissenschaft 49 125129
Law, A. J. R., Leaver, J., Banks, J. M. & Horne, D. S. 1993 Quantitative fractionation of whey proteins by gel permeation FPLC. Milchwissenschaft 48 663666
Le Graet, Y. & Brule, G. 1993 The mineral equilibria in milk: effect of pH and ionic strength. Effects of pH and ionic strength on distribution of mineral salts in milk. Lait 73 5160
Noh, B. & Richardson, T. 1989 Incorporation of radiolabeled whey proteins into casein micelles by heat processing. Journal of Dairy Science 72 17241731
Pouliot, Y., Boulet, M. & Paquin, P. 1989 Observations on the heat-induced salt balance changes in milk. I. Effect of heating time between 4 and 90°C. Journal of Dairy Research 56 185192
Rose, D. 1968 Relation between micellar and serum casein in bovine milk. Journal of Dairy Science 51 18971902
Rose, D. & Tessier, H. 1959 Composition of ultrafiltrates from milk heated at 80 to 230°F in relation to heat stability. Journal of Dairy Science 42 969980
Singh, H. & Fox, P. F. 1987 Heat stability of milk: role of β-lactoglobulin in the pH-dependent dissociation of micellar κ-casein. Journal of Dairy Research 54 509521
Smits, P. & Van Brouwershaven, J. H. 1980 Heat-induced association of β-lactoglobulin and casein micelles. Journal of Dairy Research 47 313325
Tamime, A. Y. & Robinson, R. K. 1988 Fermented milks and their future trends. Part II. Technological aspects. Journal of Dairy Research 55 281307
Van Hooydonk, A. C. M., De Koster, P. G. & Boerrigter, I. J. 1987 The renncting properties of heated milk. Netherlands Milk and Dairy Journal 41 318
Van Hooydonk, A. C. M., Hagedoorn, H. G. & Boerrigter, I. J. 1986 pH-induced physico-chemical changes of casein micelles in milk and their effect on renneting. 1. Effects of acidification on physico-chemical propcrties. Netherlands Milk and Dairy Journal 40 281296
Van Vliet, T. & Keetels, C. J. A. M. 1995 Effect of preheating of milk on the structure of acidified milk gels. Netherlands Milk and Dairy Journal 49 2735
Visser, J., Minihan, A., Smits, P., Tjan, S. B. & Heertje, I. 1986 Effects of pH and temperature on the milk salt system. Netherlands Milk and Dairy Journal 40 351368

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Effects of heat treatment and acidification on the dissociation of bovine casein micelles

  • Andrew J. R. Law (a1)


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