Recovery of γ-Oryzanol from Rice Bran Acid Oil by an Acid-base Extraction Method with the Assistance of Response Surface Methodology

A rapid and low energy consumption method for the recovery of gamma-oryzanol from rice bran acid oil (RBAO), a byproduct of rice bran oil (RBO) refining, is presented. The RBAO was converted to the fatty acid ethyl ester (FAEE) and was used as the starting material. The dissolved gamma-oryzanol was separated from the FAEE using an acid-base extraction method with alkaline aqueous ethanol and hexane as extraction media. A systematic investigation of the extraction yield was carried out by applying response surface methodology (RSM) based on central composite design (CCD) and Derringer's desirability function. The concentration of NaOH, the percentage of ethanol in water, the hexane content and their interactions showed significant effects on the yield of gamma-oryzanol and FAEE. The optimal extraction conditions were as follows: extraction time of 1 min at room temperature (28-32 degrees C); extraction medium: 1.855 M NaOH; 75.91% ethanol in water and 20.59% hexane in the total volume of the extractant; and FAEE to extractant ratio of 1:10 corresponding to a maximum gamma-oryzanol yield of 75.81 +/- 3.44% and the desired FAEE yield of 54.42 +/- 7.80%. The gamma-oryzanol-rich fraction was further purified by washing with a 2% Na2CO, solution, obtaining 69.94% recovery yield with 89.90% purity of gamma-oryzanol. The purified gamma-oryzanol showed good scavenging activity on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and the ABTS radical and was comparable to the commercial product, clearly suggesting that the presented process was efficient and feasible.