[Amino acid composition of the unresorbed peptide fractions of the distal part of the small intestine in rats. II. Feeding of field-bean protein isolate with and without the addition of dialdehyde starch and of protein texturates from it].

Rats were fed diets containing 20% protein in the form of casein, protein isolate from sunflower seeds, protein isolate from field beans, model protein texturate made from field-bean protein isolate or model protein texturate made from field-bean protein isolate treated with dialdehyde starch and a nitrogenfree diet. The content in the distal small intestine of the rats was collected 3 hours after feeding, and the amino-acid compositions of the TCA-precipitable and TCA-soluble peptides (after separation of free amino acids) of the content were studied. The comparison of the amino-acid compositions of the two peptide fractions with the respective dietary protein showed no agreement. On the contrary, the comparison of the amino-acid compositions of the two peptide fractions determined after protein-free diet with those found after protein ingestion were in good agreement, independently of the kind of dietary protein. The comparison of the two peptide fractions with one another revealed an increased degree of proteolytic decomposition of the TCA-soluble peptides. As compared to the other protein-containing diets and to the protein-free diet, diets containing field-bean protein caused an increase of TCA-precipitable peptides and an increase of glycine in both fractions. This was also observed in model protein texturates containing only 30% field-bean protein. Treatment with dialdehyde starch produces certain alterations of the basic amino acids and their accumulation in the fractions of undigested peptide.