Recovery of γ-oryzanol from rice bran oil soapstock derived calcium soap: Consideration of Hansen solubility parameters and preferential extractability in various solvents

Abstract This study aimed to develop an effective procedure for the recovery of γ-oryzanol through calcium (Ca)-induced precipitation of rice bran oil soapstock (RBOS), a by-product of the RBO industry. The most suitable pretreatment condition was found to be saponification with sodium hydroxide at 2x the saponification value, 90 °C for 40 min, providing 100% and 63.5% conversion of triglycerides and free fatty acids, respectively, and a 79.4% γ-oryzanol yield. Addition of calcium chloride (CaCl2) solution at 0.3 g CaCl2:1 g of sodium soap (Na-FA) effectively induced the precipitation of γ-oryzanol-containing calcium soap (Ca-FA). Based on experimental solubility measurements, theoretical Hansen solubility parameters (HSPs), and a preferential extractability study, the most suitable extraction solvents were suggested to be ethyl acetate and furfural. Ethyl acetate gave a γ-oryzanol selective extractability and recovery of 55.4% and 59.3%, respectively, whilst those for furfural were 55.3% and 62.8%, respectively. In addition to obtaining a high γ-oryzanol yield in a relatively simple and energy efficient process, Ca-FA residue, a high price animal feed supplement, was also obtained by this proposed process.