Novel antioxidant peptides identified in millet bran glutelin-2 hydrolysates: Purification, in silico characterization and security prediction, and stability profiles under different food processing conditions

Abstract

Based on a model generated from response surface methodology, the optimum hydrolysis conditions of millet bran glutelin-2 (MBG-2) were obtained with a concentration of Papain of 8.17 mg/g MBG-2, at pH 7.83 and 51.6 °C for 5.9 h. Through Sephadex G-15 gel chromatography, RP-HPLC and UPLC-ESI-MS/MS analysis, three novel antioxidant peptides (CFMTY, CTGTPYC and RGLLLPSMSNAP) were identified in MBG-2H. The antioxidant activity, stability profiles of these peptides against different pH values, thermal treatments, treatment of glucose and NaCl, and simulated gastrointestinal digestion were studied. Moreover, the physicochemical property, potential toxicity and allergenicity were predicted in silico. Results showed that CFMTY, CTGTPYC and RGLLLPSMSNAP all had no potential toxicity and allergenicity, and showed high scavenging activity on ABTS+ (IC50: 80.85, 87.78 and 214.17 μmol/L), ·OH and superoxide radical. Both CFMTY and CTGTPYC showed excellent ferrous chelating ability (98.97%–99.24%, at 100 μg/mL) which was close to Glutathione. Moreover, these peptides were relatively stable against different pH values (2.0–8.0), pasteurization conditions and treatments of glucose and NaCl (<4 mg/mL). These peptides except RGLLLPSMSNAP were resistant to the gastrointestinal digestion. Therefore, the antioxidant peptides derived from MBG-2H have potential to be added into foods for preservation.