Urea-based fractionation of seed oil samples containing fatty acids and acylglycerols of polyunsaturated and hydroxy fatty acids

The selectivity and efficiency of urea complex (UC) formation-based fractio nation of free fatty acids (FFA) were examined. A rapid, simple, and inexpe nsive procedure recently developed for urea fractionation was applied to li pid mixtures containing various polyunsaturated and hydroxy FFA species. Ur ea treatment proved useful for isolating polyunsaturated FFA (PUFA) from FF A derived from fish, borage, and linseed oils by removal of saturated and m onounsaturated FFA, but was not effective for isolating hydroxy FFA from th e FFA derived from castor, Lesquerella, and Dimorphotheca oils. In situatio ns where FFA within the crystalline or UC phase were rich in PUFA, the urea /PEA mole ratio of the UC was relatively higher, with lower recovery of FFA in this phase. The distribution of urea between the crystalline phase and the solvent was not significantly affected by the FFA composition of feed n or the overall ratio of FFA to urea. It was strongly dependent on the overa ll mass fraction of solvent. Phospholipids and mono-, di-, and triacylglyce rols were poor templates for UC formation relative to FFA. Their inclusion in acylglycerol mixtures containing FFA reduced UC formation.