Angiotensin-I-converting enzyme inhibitory activities of gastric and pancreatic proteinase digests of whey proteins

Enzymatic hydrolysates of bovine beta-lactoglobulin (beta-Lg), alpha-lactalbumin (alpha-La) and whey protein concentrate (WPC) were analysed for their angiotensin-l-converting enzyme (ACE) inhibitory activity. The unhydrolysed substrates gave very low ACE inhibitory indices, i.e. < 10%. Hydrolysis of the whey proteins by pepsin, trypsin, chymotrypsin and the commercially available enzyme preparations, Corolase PP and PTN 3.0S, resulted in high ACE inhibition indices, i.e. 73-90%. Hydrolysates generated with elastase displayed relatively low ACE inhibitory activity. The order of trypsin and pepsin addition during the hydrolysis of cc La and beta-Lg did not appear to affect the ACE inhibitory activity of the resulting hydrolysate. Preliminary studies indicated that ultrafiltration through 3 and 1 kDa molecular mass cut-off membranes may be exploited to enrich for ACE inhibitory peptides. The ACE IC50 inhibition values obtained for ultrafiltered tryptic digests of beta-Lg and WPC ranged from 130-201 mg L-1. The potential application of whey protein hydrolysates as nutraceuticals in the prevention of hypertension is discussed. (C) 1997 Elsevier Science Ltd. All rights reserved.