Abstract:Milk casein was digested by in vitro simulated gastro-intestinal fluid, and ACE inhibitory activity was used as an indicator in this study. Peptide spectrum of hydrolyzate was determined by LC-MS/MS, and its absorption was studied by intestinal model in rats. The results showed that the digestibility of artificial gastric juice digestion, artificial intestinal juice digestion and the combination of gastrointestinal juice increased with time, the ACE inhibition rates of monogastric and single intestinal digestion increased rapidly with the prolongation of hydrolysis time, followed by a gradual decrease, while the combination of gastric and intestinal digestion ACE inhibitory rate decreased first and then increased. The highest degree of hydrolysis of gastrointestinal combined digestion was 25.51%, and the ACE inhibition rate reached the highest value of 68.03% at 2 h; The peptide profiles of digestive juice were determined by LC-MS/MS. The results showed that ACE inhibitory peptides (including IPP, RYLGY, LHLPLP, AYFYPEL, RPKHPIKHQ and WQVLPNAVPAK) could be produced after simulated digestion. In vitro simulated digestion was performed using FITC labeled casein, SDS-PAGE and Tricine-PAGE showed that the fluorescent labeling FITC-casein was stable after the gastrointestinal digestion, and the molecular weight of the hydrolyzate was under 5kDa. The model of intestinal absorption in the rat showed that the intestinal absorptivity order of the labeled casein in the intestinal tract after digestion was as follows: duodenum absorption > jejunal absorption > ileal absorption > colon absorption, mainly absorbed in the duodenum.
