Wet Extraction of γ-Oryzanol From Rice Bran

Abstract

γ-oryzanol is unique to rice bran oil (RBO) and it is known to be a potent hypocholesterolemic agent. Separation and isolation of γ-oryzanol from crude RBO is difficult due to complexity of components in crude RBO. Converting acylglycerides and FFA in RBO into FAME will concentrate bioactive compounds in the residue after FAME was removed from the RBO-based biodiesel. In this study, wet-extraction of bioactive compound from rice bran, γ-oryzanol, has been carried out using subcritical water-methanol mixture. The effects of extraction temperature, extraction time, water-methanol volume ratio and pressurizing gas type on the content and recovery of γ-oryzanol in crude RBO-based biodiesel have been investigated. It was found that the content and recovery of γ-oryzanol in RBO-based biodiesel increased with higher extraction temperature, longer extraction time and lower water concentration. The content of γ-oryzanol in RBO-based biodiesel was higher under N2 atmosphere since CO2 can acidify the solvent leading to hydrolysis of γ-oryzanol. The maximum γ-oryzanol content in RBO-based biodiesel was 2.16 % (corresponding to 2750 mg γ-oryzanol/kg rice bran) obtained after extraction for 7 h at 200 °C and 40 bar with water concentration of 50 % (v/v) under N2 atmosphere.