37-10

N. T. DUNFORD and J. W. King. Food Quality and Safety Research, National Center for Agricultural Utilization Research, Agricultural Research Service, USDA, 1815 North University Street, Peoria, IL 61604

Sterols occur as minor components in most natural oils and fats. Sterols consist of a hydrophobic tetracyclic backbone with an aliphatic side chain and a hydrophilic hydroxyl group. However, phytosterols present in plants differ from cholesterol by a methyl or ethyl group in their side chain. Sterol recovery from oils is of interest because the sterols can be used as the starting material for the synthesis of synthetic vitamin D and sex hormones. Although sterols isolated from soybeans were shown to have a cholesterol-lowering effect in the 1950s, it is only recently that phytosterols have become important commercially in the food industry as a result of the increasing consumer demand for nutraceuticals/functional foods. Plant sterols traditionally have not been a concern to the processors, since they have been perceived as inert, and of no significance in the properties of the oil. Conventional oil refining processes remove a significant portion of the phytosterols present in crude vegetable oils.

This study examines supercritical fluid fractionation technology as an alternative oil refining process to obtain phytosterol-enriched fractions from crude vegetable oils.

An eight-foot column with Propack internals, operating semicontinuously, was used for the fractionation experiments. Crude rice bran, corn, corn fiber, and soybean oils which were commercially extracted with hexane were used as feed materials to the column. The effect of pressure (135-340 bars), both isothermal and temperature gradient (40-80^oC) operation of the column, and fractionation time on the composition of the resultant fractions was examined. Compositions of the extract and raffinate fractions were analyzed for steryl fatty acid ester, free sterol, and ferulate ester content.

A comparison of the phytosterol content of the raffinate samples from the SC-CO₂ fractionation column with commercially refined rice bran, corn, and soybean oils from conventional extraction and refining processes indicated that the SC-CO₂ fractionation technique could yield phytosterol-enriched edible oils.