GRADIENT DENSITY ISOLATION AND FRACTIONATION OF HAZE-CAUSING SOLIDS OF CANOLA OIL

An occasional problem in retail canola (Brassica sp) oil is a precipitate or haze. By combining centrifugation at 2 degrees C and an aqueous-methanol flotation medium of an appropriate density the bulk of the triacylglyceride oil could be cleanly removed from the haze solids. The residue of solids could then be divided, also at 2 degrees C, into a hexane-insoluble fraction (HIP) of C-42-C-63 normal and branched-chain wax esters, and a hexane-soluble fraction (HSP) including steryl esters and sometimes shorter chain (C-42-C-46) wax esters. However, the HSP was primarily composed of triacylglycerides with an unremarkable fatty acid composition similar to that of the original oil. The application of infrared and nuclear magnetic resonance spectroscopy, of gas chromatography, and of Chromarod-Iatroscan thin-layer chromatography with flame-ionisation detection to the HIP and HSP identifications is described. Phospholipids were found only in crude oils and do not appear to contribute to the haze in refined retail oils.