Mechanism for the ethanol-dependent: Heat-induced dissociation of casein micelles

An explanation as to how casein micelles dissociate when heated in the presence of ethanol is presented. Dissociation of casein micelles in milk-ethanol mixtures was studied using ¹H 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 quality of milk serum, but above a critical temperature (∼30 °C in a 35% ethanol solution), ethanol enhances solvent quality and dissociates the casein micelles. Ethanol reduced protein hydrophobicity and increased the pK_a value of phosphoserine, effects that are likely to be significant in the dissociating effect of ethanol at elevated temperatures.