Stability and antioxidant activities of corn protein hydrolysates under simulated gastrointestinal digestion

Background and objectives Bioactive peptides are expected to be ingested orally; it is important to study the effect of simulated gastrointestinal (GI) digestion on the stability and antioxidant activity of these peptides. Findings After simulated GI digestion, degree of hydrolysis of corn protein hydrolysates (CPH) significantly increased from 22.7% to 39.4% while 77.5% peptides were still retained. Compared to the undigested CPH, the final CPH digests exhibited excellent antioxidant activity, including 1,1‐diphenyl‐2‐picrylhydrazyl radical 2,2‐diphenyl‐1‐(2,4,6‐trinitrophenyl) hydrazyl radical scavenging activity (12.9% increase), hydroxyl radical scavenging activity (4.1% increase), and reducing power (50.9% increase), but lower inhibition rate of linoleic acid peroxidation (41.5% decrease). The free amino acids including Pro, Asp, and Glu maintained at a low proportion during the entire course of digestion. Two GI‐resistant antioxidant peptides (Tyr‐Pro‐Gln, 406.45 Da; Ala‐Tyr‐Leu, 365.43 Da) were purified with multistep chromatography and identified by UPLC‐ESI‐MS. Conclusions The CPH digests exhibited excellent antioxidant activity after simulated GI digestion. The results suggested that CPH obtained by alcalase digestion are potential functional foods or nutraceuticals due to their content of bioactive peptides. Significance and novelty Some peptides containing Pro, Asp, and Glu had a strong ability to resist digestion. Two novel antioxidant peptides have been purified and identified from the CPH digests.