Influence of storage of milk on casein distribution between the micellar and soluble phases and its relationship to cheese-making parameters

Abstract

Summary The influence of storage time and temperature on the distribution of individual milk proteins between the micellar and soluble phases has been examined. Storage at 4 or 7 °C is accompanied by a dissociation of micellar caseins, particularly β-casein, into the soluble phase during the first 48 h, but on further storage there is a partial reversal of this process. At higher storage temperatures (10–20 °C) the contents of all the individual caseins in the soluble phase decrease throughout storage. During cheese–making, losses of fat and curd fines in whey were greater with increased soluble phase casein and clotting times were prolonged. Curd structure was weaker, curds were more moist and slightly lower cheese yields were obtained in stored milks with elevated soluble–phase casein. When milks were stored for up to 3 d at 4 °C cheese gradings were virtually unaffected by storage, but higher temperatures (10–15 °C) led to cheeses being downgraded, largely for body and texture defects but also for flavour after 3 d. Attempts to reverse the pattern of casein dissociation and to minimize the detrimental effects of milk storage on subsequent cheese-making showed that a heat treatment of 30 min at 60 °C was the most beneficial.