Extraction of α-tocopherol and γ-oryzanol from rice bran

The aim of this research was to study the effect of operating mode (continuous versus batch + continuous), temperature, pressure and solvent on alpha-tocopherol and gamma-oryzanol extraction from rice bran (Oryza sativa Linn.) and compare the efficiency of three extraction methods: SC-CO2 extraction, solvent extraction and soxhlet extraction. Three sets of experiments were performed. First, extraction using SC-CO2 was performed over a range of temperatures and pressures (45-65 degrees C and at 38 and 48 MPa), and at a CO2 flow rate of 0.45 mL/min. The results showed that the best conditions for alpha-tocopherol extraction were 55 degrees C, 48 MPa in the batch + continuous mode. For gamma-oryzanol, the best conditions were 65 degrees C, 48 MPa and in the continuous mode. In the second set of experiments, solvent extraction using hexane and ethanol at 32 and 55-60 degrees C was studied. The results showed that none of the solvents could extract alpha-tocopherol; however, ethanol at 55-60 degrees C was suitable for gamma-oryzanol extraction. Finally, soxhlet extraction experiments using hexane for alpha-tocopherol and ethanol for gamma-oryzanol were also performed. In summary, SC-CO2 was found to be the best solvent for extracting both alpha-tocopherol and gamma-oryzanol from rice bran, because of its higher yields and extraction rate. (C) 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.