Mechanism for the ethanol-dependent heat-induced dissociation of casein micelles

An explanation as to how casein micelles dissociate when heated in the pres ence of ethanol is presented. Dissociation of casein micelles in milk-ethan ol mixtures was studied using H-1 NMR, and the effects of addition of CaCl2 , NaCl, or EDTA or alteration of milk pH on this dissociation were studied. It is proposed that at low temperatures, ethanol reduces the solvent quali ty of milk serum, but above a critical temperature (similar to 30 degreesC in a 35% ethanol solution), ethanol enhances solvent quality and dissociate s the casein micelles. Ethanol reduced protein hydrophobicity and increased the pK(a) value of phosphoserine, effects that are likely to be significan t in the dissociating effect of ethanol at elevated temperatures.