Properties of casein micelles reformed from heated mixtures of milk and ethanol

Abstract

Addition of an aqueous solution of ethanol (>30% ethanol) to skim milk, followed by heating to >60 °C, resulted in the mixture becoming translucent; objectively, its Hunter L-value was reduced. The degree of translucence increased with increasing ethanol concentration and temperature; the effect was not fully reversible on cooling, as cooled mixtures had higher turbidity values than unheated mixtures. Following removal of ethanol by vacuum rotary evaporation and readjustment to the original milk solids concentration, the milk contained large protein aggregates (referred to as reformed micelles), the properties of which were studied. Milk containing reformed micelles had a type B heat coagulation time–pH profile and was less stable to ethanol than control milk. The mechanism responsible for these changes in the properties of milk appeared to be independent of calcium or other milk salts, but was probably linked to ethanol-induced denaturation of whey proteins.