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Effect of β-lactoglobulin and precipitation of calcium phosphate on the thermal coagulation of milk

Published online by Cambridge University Press:  20 March 2001

JOHN E. O'CONNELL
Affiliation:
Department of Food Chemistry, University College, Cork, Irish Republic Present address: NIZO, NL-6710 BA Ede, The Netherlands (connell@nizo.nl).
PATRICK F. FOX
Affiliation:
Department of Food Chemistry, University College, Cork, Irish Republic

Abstract

The effect of β-lactoglobulin and heat-induced precipitation of calcium phosphate on the pH dependence and mechanism of thermal coagulation of milk throughout the pH range 6·3–7·3 was studied using serum protein-free milk and sodium caseinate as models for micellar and non-micellar milk protein systems respectively. It appears that the specific effect of β-lactoglobulin at the pH of maximum stability may be related to its ability to chelate calcium. The effect of β-lactoglobulin at the pH of minimum stability does not appear to be directly related to heat-induced dissociation of κ-casein or micellar integrity but may be due to its ability to sensitize casein micelles to heat-induced precipitation of calcium phosphate, by increasing micellar hydrophobicity. The extent of heat-induced precipitation of calcium phosphate, as a function of pH, is an inverse reflection of the pH dependence of heat stability. Micellar integrity appears to play a critical role in the heat stability of milk but for reasons not previously appreciated.

Type
Original article
Copyright
Proprietors of Journal of Dairy Research 2001

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