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 γ-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 γ-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 γ-oryzanol and FAEE. The optimal extraction conditions were as
follows: extraction time of 1 min at room temperature (28-32℃); 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 γ-oryzanol yield of 75.82±3.44% and the desired FAEE yield of
54.42±7.80%. The γ-oryzanol-rich fraction was further purified by washing with a 2% Na2CO3 solution,
obtaining 69.94% recovery yield with 89.90% purity of γ-oryzanol. The purified γ-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.