Comparison of supercritical fluid and solvent extraction methods in extracting γ-oryzanol from rice bran

Organic solvents were compared with supercritical CO2 relative to efficiency for extracting lipid and gamma-oryzanol from rice bran. A solvent mixture with 50% hexane and 50% isopropanol (vol/vol) at a temperature of 60 degrees C for 45-60 min produced the highest yield (1.68 mg/g of rice bran) of gamma-oryzanol among organic solvents tested. The yield of gamma-oryzanol without saponification was approximately two times higher (P < 0.05) than that with saponification during solvent extraction. However, the yield (5.39 mg/g of rice bran) of gamma-oryzanol in supercritical fluid extraction under a temperature of 50 degrees C, pressure of 68,901 kPa (680 atm), and time of 25 min was approximately four times higher than the highest yield of solvent extraction. Also, a high concentration of gamma-oryzanol in extract (50-80%) was obtained by collecting the extract after 15-20 min of extraction under optimized conditions.