ENZYMATIC-HYDROLYSIS PRETREATMENT FOR MECHANICAL EXPELLING OF SOYBEANS

Mechanical expelling of soybeans with enzymatic hydrolysis as pretreat ment was investigated, and the process parameters were optimized by me ans of response surface methodology. Enzyme pretreatment enhanced both the amount of extractable oil in soybeans and oil extractability. A s econd-order response surface model was developed to predict the expell ed oil as a function of the six process parameters investigated. The o ptimum was found at: Moisture content during hydrolysis, 23.00% wet ba sis (w.b.); enzyme concentration, 11.84% vol/wt; incubation period, 13 .24 h; moisture content during pressing, 9.36% w.b.; pressing pressure , 75 MPa; and pressing time, 5.36 min. The parameters had no interacti ve effects on expelled oil. Pressing pressures above 75 MPa caused ext rusion. Under the optimal conditions, oil expelled from dehulled crack ed soy-beans by static pressing at room temperature (18-degrees-C) was 63.5% of the total extractable oil. Much higher oil recovery would be expected in actual screw expellers due to dynamic pressing and higher operating temperature. Oil recovery could be further increased by add ing one or more conventional pretreatments to the enzymatic hydrolysis pretreatment investigated in this study.