CASEIN INTERACTIONS - CASTING LIGHT ON THE BLACK-BOXES, THE STRUCTUREIN DAIRY-PRODUCTS

This paper reviews the literature on the interactions of the caseins a nd suggests that the state of association of these proteins is governe d by a balance of attractive hydrophobic interactions and electrostati c repulsion. The effects of temperature, pH and ionic strength on the self-association and calcium-induced aggregation of the individual cas eins are rationalized in terms of their influence on this balance of f orces. The discussion is then extended to the nature of the interactio ns prevailing in the casein micelle and a dual-bonding model of the ca sein micelle is formulated, reflecting the need for two different form s of bonding in the network. This model plausibly accounts for the eff ects of temperature, pH, ionic strength, micellar dissociating agents and solvent on the integrity of the micelle in terms of their influenc e on the hydrophobic/electrostatic balance of forces. Finally, it is p ostulated that the same type of bonding prevails in casein gels produc ed by renneting or acidification. The model is then used to explain th e influence of temperature on rennet gel strength, the effects of fore warming on rennet and acid coagulation properties of milk, and the eff ect of temperature on the viscoelastic properties of a concentrated mi cellar suspension. (C) 1998 Elsevier Science Ltd. All rights reserved.