Kaina Qiao,Xuewei Zhou,Huimin Wu,Lili Zhang,Li Liang,Yuyu Zhang
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.
Yeast, identified as a microorganism, boasts a considerable protein content, positioning yeast protein as a highly promising alternative in the quest for sustainable protein sources. The primary aim of this study is to evaluate the protein quality of yeast protein and compare it with animal proteins (whey concentrate/isolate proteins) and plant proteins (soy, wheat, pea proteins). Notably, yeast protein exhibits the highest ratio of indispensable/dispensable amino acids (IAAs/DAAs, 0.91). However, in both in vivo and in vitro digestion experiments, yeast protein demonstrated lower true protein digestibility (TPD) and true ileal digestibility (TID) compared to other proteins. Despite this, the yeast protein's amino acid score (AAS, 1.37 for >3 years), protein digestibility-corrected amino acid score (PDCAAS, 100 % for >3 years), and digestibility-corrected amino acid score (DIAAS, 82.42 % for >3 years) of yeast protein surpassed those of plant proteins, yet remained lower than animal proteins primarily due to its lower digestibility.