HYDROLYSATES FROM PROTEOLYSIS OF HEAT-DENATURED WHEY PROTEINS

Whey protein isolate was denatured at 85 degrees C, pH 4.6 for 30 min to produce heat denatured whey protein isolate (HDWPI) which was hydrolyzed with trypsin, chymotrypsin, Alcalase or Neutrase to 2.8, 4.3, 6.0 or 8.0% degree of hydrolysis (DH). Analysis of freeze-dried fractions revealed a linear increase in primary amino groups, non-protein nitrogen and ash contents. Polyacrylamide gel electrophoresis showed that high and intermediate molecular weight peptides were converted to lower molecular weights with progress of hydrolysis. Differences in proteolysis patterns were observed with different enzymes. The time required to achieve equivalent hydrolysis at 1, 2, 3 or 4% enzyme/substrate ratio varied with the type of enzyme and DH.