Enzymatic hydrolysis as a green alternative for glyceride removal from rice bran acid oil before γ-oryzanol recovery: Statistical process optimization

Abstract

Rice bran acid oil (RBAO) is a byproduct of rice bran oil refinery, comprising of free fatty acids (FFAs), glycerides, and considerable amount of the natural antioxidant, γ-oryzanol. As a primary step to recover γ-oryzanol from RBAO, glycerides must be removed by conversion into more easily separable components such as FFAs. In this study, enzymatic hydrolysis was proposed as a green alternative to conventional base-catalyzed hydrolysis for glyceride removal from RBAO. The face-centered central composite rotatable design was used to investigate the effects of three independent variables: time, temperature, and water:RBAO ratio, and their interactions on the responses: glyceride removal, γ-oryzanol loss, and FFA production, and to determine the statistical models describing their relationships. In addition, by applying the desirability function approach, the optimal location was identified, corresponding to maximal glyceride removal with an imposed upper limit of 35% γ-oryzanol loss. At an established optimal condition of 22 h, 48.5 °C and 1:1 water:RBAO ratio, the experiments in which the enzymatic hydrolysis was carried out at 1x and 10x reaction scales confirmed the validity of the models: glyceride removal approached completion (99%), γ-oryzanol loss was as low as 32%, and the FFA production was 73–75%, falling within the 95% prediction interval. The results of this study demonstrated that the enzymatic hydrolysis is a promising method for glyceride removal prior to recovery of γ-oryzanol from RBAO, and that the statistical models gave accurate predictions of responses and would be useful further industrial design of the process.