Effect of a proteolitic enzyme preparation (alcalase) on whey proteins

When acid whey samples were adjusted to pH 7.5 and incubated with a commercial proteolytic enzyme preparation (alcalase), the turbidity of the solution gradually increased until a soft coagulum, composed of small-sized aggregates, formed after about 1 h. Under the same conditions, sweet whey produced no coagulated material unless CaCl2 was added. Aggregate formation was enhanced by CaCl2 addition in both wheys, but especially in acid whey. However, maximum aggregate formation in terms of protein recovery was about 28%. The precipitated material obtained with various amounts of Ca++ in both sweet and acid wheys resolved into two fractions when it was subjected to nondissociating gel electrophoresis. Sodium dodecyl sulfate gel electrophoresis and HPLC studies showed that the polymerized product consisted of protein fragments having an approximate molecular weight of 7000 to 10,000. A possible mechanism for enzyme-induced aggregation of these peptides is presented.