Processing of tocopherol and FA systems using a nonporous denser polymeric membrane

Tocopherols permeated preferentially over oleic acid in model systems and over oleic acid and other oil constituents during processing of soy deodorizer distillate (DOD) when using nonporous denser polymeric membranes (i.e., denser than reverse osmosis membranes). This observation was unexpected, since the separation in a denser membrane is generally based on a solution-diffusion mechanism. That tocopherols are less polar than oleic acid appears to have facilitated the preferential permeation of tocopherols through the hydrophobic membrane. Selectivity of the membrane for tocopherols improved with esterified soy DOD. The presence of FAME decreased the viscosity of the feed and thereby increased convective flow, which in turn improved permeate flux. FAME appeared to have exerted positive coupling effects with tocopherols, having better selectivity in spite of the greater solubility of FAME in the membrane material. Membrane selectivity for tocopherols improved upon dilution of the feed material with hexane, perhaps owing to greater solubility of tocopherols in hexane (nonpolar) than other feed constituents.