Heat treatment of vegetable oils I. Isolation of the cyclic fatty acid monomers from heated sunflower and linseed oils

Abstract

Abstract Linseed and sunflower oils were heated at 275 C for 12 hr under nitrogen. The sunflower oil was also heated in a commercial fryer at 200 C for 48 hr using a 2‐hr daily cycle. The cyclic fatty acid monomers (CFAM) formed during the heat treatment of the linseed oil were isolated by a combination of saponification, esterification, column chromatography on silicic acid and urea fractionation. The isolated CFAM fraction was 99% pure, the balance being some 12:2ω6. Another step was necessary to isolate the CFAM from heated sunflower oils. The urea adduct fractionation resulted in the isolation of a nonurea adduct fraction which contained a mixture of CFAM and 18:2ω6. These were further separated using high performance liquid chromatography (HPLC) on a C18 reverse phase column. Each fraction was analyzed by gas liquid chromatography and hydrogenated to determine the content of the C18 straight chain fatty acids.