Abstract: The procedure to obtain oligopeptide with soybean protein isolate by sequential treatment with two proteinases was described.The experiment were designed:technique one(T1) kept optimum pH of proteinaseⅠfor 3h by adding NaOH,technique two(T2) kept optimum pH of proteinaseⅠonly at first 30 minutes and hydrolysate are immediately hydrolyzed by proteinaseⅡon acid and neutral condition respectively.The results showed that protein recovery rate are 86.5 %,87.8 % and acid soluble nitrogen rate are 83.2 %,86.4 % and ash contents are 11.1% and 7.0% respectively.The molecular weight distribution of peptides obtained by T1 above 5000,about 3000 and between 500 and 600 are 20.6%,3.3% and 61.3% respectively;The molecular weight distribution of peptides obtained by T2 above 5000,about 2000 and between 700 and 900 are 12.8%,5.7% and 71.3% respectively.It showed that hydrolysis condition of T2 is better than T1’s.

Key words: proteinaseⅠ, proteinaseⅡ, soybean protein isolate, oligopeptide