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

Enzymatic hydrolysates of bovine β-lactoglobulin (β-Lg), α-lactalbumin (α-La) and whey protein concentrate (WPC) were analysed for their angiotensin-I-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 α-La and β-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 β-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.