Abstract: Objective: To clarify the amino acid composition and absorption kinetics of yeast protein (YP), whey protein concentrate (WPC), and whey protein isolate (WPI) in rats. Methods: After single gavage administration of the three proteins at an equal dose, the dynamic changes of plasma amino acids in rats were investigated. Meanwhile, the regulatory effect of leucine (Leu) fortification on plasma amino acid metabolism was explored. Results: The crude protein content of YP was similar to that of WPI, and the contents of multiple essential and functional amino acids including valine, isoleucine, phenylalanine, histidine, and arginine in YP were higher than those in the WPC and WPI. Plasma amino acid concentrations peaked at 30 min after gavage administration of the three proteins, with peak levels in the order of WPI > YP > WPC. From 60 to 120 min after gavage, the plasma amino acid concentration in the YP group decreased slowly, showing sustained-release and long-acting absorption characteristics. After equal-dose Leu fortification, the area under the plasma amino acid concentration-time curve (AUC) of valine was significantly higher in the Leu-fortified YP (YP-L) group than in the Leu-fortified WPI (WPI-L) and Leu-fortified WPC (WPC-L) groups (P < 0.05). The AUCs of Leu, isoleucine, and total branched-chain amino acids (BCAAs) were significantly higher than those in the WPC-L group (P < 0.05), but showed no significant differences from those in the WPI-L group (P > 0.05) despite an upward trend. Conclusion: YP has excellent amino acid composition and sustained-release long-acting absorption properties, and exhibits superior bioavailability of BCAAs at equal levels of Leu fortification. It is a novel high-quality non-animal-derived protein with great development and application prospects.

Key words: yeast protein; whey protein; amino acid; kinetics; rat plasma