Observations on Protein Digestion in vivo

Abstract

Concentrations of free amino acids in the portal and systemic blood plasma of rats force-fed zein, casein, or their respective hydrolyzates were determined in an effort to show a relationship between the change in plasma amino acid pattern and the relative digestibility of the proteins. Force-feeding zein had little effect on the concentrations of free amino acids in the portal and systemic plasma but force-feeding casein caused a substantial increase in the concentrations of free amino acids in the portal plasma. When hydrolyzates of these proteins were force-fed, much larger increases in the plasma free amino acid concentrations were observed with the largest responses occurring after ingestion of casein hydrolyzate.