EFFECTS OF PROCESSING TREATMENT AND CHEESE-MAKING PARAMETERS ON FOAMING PROPERTIES OF WHEY-PROTEIN ISOLATES

Acid whey from raw milk, acid whey from pasteurized milk, and sweet wh ey from Cheddar cheese making were prepared from one batch of milk. Ea ch whey was dialyzed and freeze-dried to produce a whey protein isolat e containing > 90% protein on a dry basis. Foaming characteristics (ov errun and foam stability) of aqueous solutions (5% protein, pH 7.0) of each whey protein isolate were measured. Foaming characteristics were poor for whey protein isolate prepared from untreated acid whey and s weet whey. Following centrifugation to remove insoluble foam depressan ts, the foaming characteristics of whey protein isolate prepared from acid whey and sweet whey were improved slightly. Following centrigatio n plus microfiltration of the acid and sweet whey protein isolates wit h cellulosic membranes (.22-mum), the overrun and foam stability were greatly improved, very consistent, and comparable with die foaming pro perties of egg white and commercial whey protein isolate, in spite of fat contents of 2 to 4% on a dry basis. Whey pasteurization and cheese -making parameters (i.e., coagulant, starter media, color, and bleachi ng agent) did not influence the foaming characteristics of whey protei n isolate. Microfiltered acid whey protein isolate and sweet whey prot ein isolate had very different glycomacropeptide contents but similar foaming properties. The foam depressant in whey originates from raw mi lk.