Effect of subcritical solvent extraction conditions on amount of γ-oryzanol and γ-tocopherol in dawk pa-yom rice bran oil

Abstract

This research focused on the subcritical solvent extraction of phytochemicals γ-oryzanol and γ-tocopherol from upland rice bran (Dawk Pa-yom variety, DY). Subcritical solvent extraction was conducted using a batch reactor. The temperature was varied in range from 80 to 120°C for 20 to 60 min. The solvents in use were ethanol, methanol, and water. γ-Oryzanol and γ-tocopherol were simultaneously analyzed by HPLC. Antioxidant activity was determined by a DPPH radical assay. Methanol was able to extract a higher level of γ-tocopherol than ethanol and water. Extraction by methanol gave higher antioxidant activity than ethanol. Even though water could not extract γ-oryzanol, it was able to extract substances with higher yield of antioxidant activity than either methanol and ethanol. Increasing the extraction temperature increased the oil yield, γ-oryzanol and γ-tocopherol paralleled increase antioxidant activity. During the extraction process, some degradation of antioxidants was observed, and this showed the importance of kinetics parameters in this research.