Effect of Digestibility of Soy Protein Concentrate on Rat Nutrition(1) : Effect of Proteolytic Pretreatment of Soy Protein Concentrate on Amino Acid Pattern in Small Intestine and Activities of Enzymes related with Digestion and Metabolism of Protein

The digestion and metabolism of protein of rats fed soy protein concentrate (SP) pretreated by protease was investigated, and the nutritive value of the pretreated SP was discussed. Glutamate-pyruvate transaminase, arginase and xanthine oxidase activities in liver of rats fed heated SP are lower than those fed SP pretreated by protease and amino acid mixture simulated SP. There is more quantity of peptide in small intestine of rats fed SP pretreated by protease than that fed the amino acid mixture. In free amino acid pattern, however, no difference was shown between SP groups, but the patterns of SP groups, especially on the bases of methionine content, were different with that of amino acid mixture group. No difference is shown in the digestion and the biological values between SP groups. From these results, it was found that the pretreatment of SP by protease, which might improve the digestibility of SP, was effective for raising the availability of SP. It may be considered, furthermore, that methionine in SP is difficult to liberate in small intestine, which causes a wasteful absorption of amino acids for rat.