The effect of in vitro simulated digestion on peptide release of Torreya grandis meal proteins and bioactivity assessment of the hydrolysates

The Torreya grandis meal (TGM) is a protein-rich by-product during the seed oil manufacturing process. In this study, the T. grandis meal protein (TGMP) was extracted from the defatted TGM by alkali extraction and isoelectric point precipitation, and the effect of in vitro digestion on peptide release of the TGMP was evaluated using static digestion model. The TGMP was composed of 17 amino acids with the molecular weight was major located at 35 kDa by SDS-PAGE. Under simulated digestion, the variation in peptide content, amino acid composition, and molecular weight distribution of the hydrolyzed TGMP were determined. The degree of hydrolysis (DH) of TGMP was revealed to be 16.52% after 120 min of gastric digestion and 18.85% after 270 min of gastrointestinal digestion, indicating that the simulated digestion is insufficient to hydrolyze the TGMP thoroughly. Meanwhile, the bioactivity assessment suggested that the antioxidant and anti-tyrosinase activity of the TGMP was significantly enhanced after simulated digestion. The obtained results would provide valuable information on the digestive characteristics of TGMP in the gastrointestinal tract, and would also help to develop functional peptides from the T. grandis meal.