Fractional extraction of rice-bran oil and its esters with supercritical carbon dioxide

The fractional extraction of rice-bran oil and its esters with supercritical carbon dioxide was studied at 313-373 K and 8.2-19.8 MPa, using an entrainer or a separation column. A column was effective for fractionating the fatty acids in the extracted rice-bran oil, while an entrainer enhanced the extraction efficiency of the rice-bran oil. No significant difference existed in the fatty acid composition of the oils extracted with supercritical CO[sub 2] alone and supercritical CO[sub 2] containing an entrainer. The degree of fractionation of the fatty acid esters from rice-bran oil increased with the temperature in the column. At 343 K, the proportion of palmitate in the extracts reached a maximum of 86% in the early fractions, but oleate and linoleate were not fractionated. The use of a column packed with silica gel-supported silver nitrate was extremely effective for fractionating fatty acid esters. Palmitate and oleate, which constituted 94% and 91% of the fatty acid esters in the initial rice-bran oil esters, were recovered in 91% and 81% purity, respectively, but the degree of recovery and the purity were both lower with linoleate than with oleate.