Abstract: In this thesis, for optimizing the hydrolysis condition of soybean protein isolated (SPI) by Protamex protease, second- order regression rotation designing has been used. The mathematics matrix was established between the degree of hydrolysis (DH) and five factor(pH value, hydrolysis time, substrate concentration, hydrolysis temperature, the ratio of enzyme and substrate). The high yield scheme and the optimization design were also determined. The optimization condition: hydrolysis time 10h, substrate concentration at 14%, the ratio of enzyme and substrate at 4.5%, pH6.5 and 40℃. By main member analysis, pH value contributes to DH mostly.

Key words: regression rotation designing, SPI, protamex protease, hydrolysis