Comparative effects of feeding a protease inhibitor-enriched potato protein concentrate and soy flour to rats

Rats were fed casein diets to which had been added a potato protein concentrate (PPC) at a level which provided trypsin- and chymotrypsin-inhibitor activities comparable to that present at the same level (10%) of protein derived from raw soy flour. Control groups consisted of the same diets in which the unheated PPC and raw soy flour were replaced by their heated counterparts in which over 90% of the inhibitor activities had been destroyed. After 5 weeks the following measurements were made: (1) growth, (2) PER, (3) pancreas weight, (4) protein digestibility, (5) a peptide test that reflects pancreatic function, and (6) enzyme activities (trypsin, chymotrypsin, amylase, and lipase) in the pancreas and small intestine. PPC was found to produce the same general pattern of effects as raw soy flour, namely, an inhibition of growth, a decrease in PER and protein digestibility, an increase in the size of the pancreas, an increase in the recovery of p-aminobenzoic acid in the peptide test, and a depletion of enzyme in the pancreas with concomitant increases in the intestines (except for trypsin). PPC was somewhat more effective than raw soy flour in causing an increase in trypsin and chymotrypsin activities in the faces.