Abstract: The optimum conditions about sequentially hydrolyzing small black-soybean protein isolated were:the small black-soybean were hydrolyzed by alkaline proteinases in the condition of pH 9.0,50 ℃ for 4 hours,and then,hydrolyzed continuously by neutral protease in the condition of pH7.0,50 ℃ for 4 hours,and the quantity of pronase is 4000U/g.The peptide yield reached 80%,and the degree of hydrolysis(DH) of black-soybean protein isolate is 32.75%.The result of gel chromatography showed that the percentage of the component of black-soybean peptides with a molecular weight below 10000 D 91.61 %.

Key words: small black-soybean peptide, double enzymolysis, peptide yield, molecular weight distribution, DH