Generation and identification of angiotensin converting enzyme (ACE) inhibitory peptides from a brewers' spent grain protein isolate

An alkaline extracted brewers' spent grain protein-enriched isolate (BSG-PI) was hydrolysed using Alcalase, Corolase PP, Flavourzyme and Promod 144MG, yielding Alc hydrolysate (H), CorH, FlavH and ProH, respectively. The degree of hydrolysis (DH) of the protein hydrolysates varied from 4.45% for ProH to 16.4% for CorH. The in vitro ACE inhibitory activity of the BSG-PI increased significantly following 15 min incubations with Alcalase, Corolase PP and Flavourzyme. The 5 kDa ultrafiltration permeates of FlavH and CorH resulted in lower ACE IC₅₀ values than their respective hydrolysates. The bioactivity of the BSG-PI hydrolysates was retained after simulated gastrointestinal digestion (SGID) while SGID also resulted in the release of ACE inhibitory peptides from the BSG-PI and ProH. UPLC-MS/MS analysis resulted in the identification of 34 peptides. Of 12 synthesised peptides, IVY and ILDL were the most potent, having ACE IC₅₀ values at 80.4 ± 11.9 and 96.4 ± 8.36 μM, respectively.