Research on the release and absorption regularities of free amino acids and peptides in vitro digestion of yeast protein.

Based on INFOGEST digestion model and Dynamic Human Stomach-Intestine in vitro (DHSI-IV), the content of free amino acids (FAAs) and peptides in yeast protein (YP) digestion products were analyzed, as well as the molecular weight distribution of digestive products. The transport and absorption of FAAs and peptides from YP static digestive products were studied by Caco-2 cells monolayer model. The highest content of branched-chain amino acids (BCAAs) and essential amino acids (EAAs) were highlighted during YP digestion. The digestibility of YP (97.66 %) was close to that of whey protein isolate (WPI), slightly higher than pea protein (PP), but significantly higher than soy protein isolate (SPI) (p < 0.05). More FAAs of YP were released in static digestion (755.40 mg/g) than in dynamic digestion (28.34 mg/g). Accordingly, more peptides of YP were released in dynamic digestion (433.76 mg/g) than in static digestion (44.44 mg/g). The intestinal phase released more FAAs and peptides than the gastric phase both static and dynamic digestion for these four proteins. Molecular weight distribution proportion of digestion products with <150 Da of the four proteins exceeded 50 %. After the absorption and transport, the absorption rate of FAAs for YP (92.75 %) was slightly lower than that of WPI. Large molecular weight peptides (>1000 Da) were not easily absorbed, and the highest distribution ratio of molecular weight with <150 Da (mainly FAAs) was detected. These proved that YP is the protein with a good quality, such as high digestive and absorption properties, which could be used as a beneficial supplement and partial replacement of animal and plant protein sources.