ABSTRACT
Pure proteins, though they contribute to the texture of foodstuffs, are said to be tasteless, but small peptides and amino acids are important in determining the flavor of various foods. The intralumenal phase of protein digestion is initiated by pepsin(s) in the acid pH of the stomach and is continued in the small intestine by the proteolytic enzymes of the pancreas. Though it is generally believed that protein digestion products enter the portal blood largely as free amino acids, certain di- and tripeptides, which are exceptionally resistant to hydrolysis, enter the portal blood stream intact and may even appear in the urine. The most recent and thorough investigation of the electrical effects of small peptides across the brush border has been reported by Ward and Boyd. Substitution of either the amino terminal or carboxy terminal groups of small peptides reduces or abolishes affinity for transport.
