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Title: PHYSTOSTEROL ENRICHMENT OF RICE BRAN OIL BY A SUPERCRITICAL CARBON DIOXIDE FRACTIONATION TECHNIQUE

Author
item Dunford, Nurhan
item King, Jerry

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Beneficial ingredients in agriculturally-derived vegetable oil products are receiving increased attention from producers and consumers alike, due to the nutritional value of these components. Compounds called sterols and steryl esters, which are found in small quantities in vegetable oils and their by-products, have cholesterol-lowering properties when routinely used. To improve consumer acceptability, shelf life, etc., extracts are desired from the above oil-derived products that maximize the concentration and effect of the cited nutritional ingredients, while removing unwanted objectable components, such as fatty acids. This research uses an environmentally benign method involving extraction and fractionation with high pressure carbon dioxide to rid rice bran oil of objectable fatty acids, thereby producing a product that is more stable and palatable to consumers. Besides the environmental benefits during processing of the oil lextract, the final products are free of objectable organic solvents, an important feature of extracts being used in the nutraceutical industry.

Technical Abstract: Rice bran oil (RBO) is a rich source of phytosterols, particularly with respect to oryzanol content. Conventional refining processes to remove free fatty acids (FFA) from such plant matrices result in a significant phytosterol loss in the oil. In this study, a high pressure fractionation process employing supercritical carbon dioxide (SC-CO2) was examined as an alternative process for reducing the FFA content of RBO while minimizing the phytosterol loss during the process. A column packed with Propack internals was used for the fractionation experiments. The effects of pressure (20.5-32.0 MPa) and temperature (45-80 deg C) for isothermal operation of the column on the composition of the resultant fractions were examined. Triglycerides (TG), FFA, steryl fatty acid esters of sterols, free sterol and oryzanol contents of raffinate and extract fractions were determined. Low pressure and high temperature conditions were found to be favorable for minimizing TG and phytosterol losses during the FFA removal from crude RBO. Rice bran oil fractions with <1% FFA, ~95% TG, ~0.35% free sterol and ~1.8% oryzanol content could be obtained utilizing the described SC-CO2 fractionation technique. Comparison of a commercially-refined RBO sample (<1% FFA, ~96% TG, ~0.2% free sterol and where no oryzanol was detected) and a SC-CO2 fractionation product indicated that the high pressure fractionation process could be a viable technique for refining crude RBO to obtain phytosterol enriched products.