Coagulation of renneted bovine casein micelles: dependence on temperature, calcium ion concentration and ionic strength

Abstract

Summary: The rates of coagulation of completely renneted casein micelles have been measured as functions of ionic strength, temperature, and concentration of Ca²⁺. At 25 °C and below, the rate constants for the coagulation were found to be low, but increased with temperature so that at 60 °C the particles were coagulating at almost maximum rate permitted by diffusion. This maximal rate at 60 °C was achieved at nearly all of the ionic strengths and concentrations of Ca²⁺ used. At lower temperatures the rate constant decreased with increasing ionic strength, the dependence being more marked at lower temperatures. Increasing concentration of Ca²⁺ also increased the rate at low and moderate temperatures. The implications of these results are discussed in terms of specific and non-specific ionic interactions and of hydrophobic bond formation.