Low-molecular weight peptide mixture and method of producing same

Abstract

A method of producing a low-molecular weight peptide mixture, comprising the steps of dissolving a first protease in a buffer solution adjusted to an optimum pH for the protease ranging from pH 3 to 10, adding at least one first protein in a buffer solution having a pH of from 3 to 10 and a concentration of 10 to 60% by weight of the protein material and thoroughly mixing the solution, adding a solution of an ester of at least one amino acid pre-formed by esterification of the amino acid with an alcohol, the pH of said buffer solution being optimum for the incorporation of said amino acid in said starting protein in the presence of said first protease in a plastein reaction, reacting said ester of at least one amino acid with said starting protein in a plastein reaction in the mixed solution whereby said at least one amino acid is covalently incorporated into said starting protein to produce a plastein reaction solution containing a modified protein, hydrolyzing said modified protein using at least one second protease having a different specificity from said at least one first protease to produce a low-molecular weight peptide mixture having an amino acid content which has different proportions of amino acids than does said starting protein, and separating from the solution said low-molecular weight peptide mixture which comprises a major proportion of dipeptides and tripeptides and containing not more than 15% by weight of free amino acids and not more than 20% by weight of a high-molecular weight fraction of compounds having a molecular weight of not lower than 700 and removable by gel filtration. The said low-molecular weight peptide mixture is readily absorbable and a useful nutrient.