Abstract: In the present study, alcalase, flavourzyme, neutral protease, bromelin, papain and different combinations of alcalase with some or all of the four other proteases were compared for their efficiency to hydrolyze soybean protein isolate (SPI) for the production of soybean oligopeptides. Alcalase provided maximum degree of hydrolysis (DH) and soybean oligopeptide yield among the five proteases. Both parameters could be improved by combining alcalase with the other proteases and maximum DH was achieved when flavourzyme and neutral protease were also used. Using response surface methodology, the optimal dosages of alcalase, flavourzyme and neutral protease were determined to be 39.6%, 25.4% and 35.0%, respectively, and the optimal total protease dosage on the basis of dry weight of SPI was 3%. A DH as high as 27.2% and an oligopeptide yield as high as 83% were obtained after 6 h of hydrolysis at 55 ℃, natural pH and an SPI concentration of 10 g/100 mL with the optimized multi-enzyme complex.

Key words: soybean oligopeptides, soybean protein isolate, protease, degree of hydrolysis (DH), response surface methodology (RSM)