Effects of antioxidants on heat-induced trans fatty acid formation in triolein and trilinolein

To elucidate the relation between heat-induced cis/trans isomerisation and thermal oxidative degradation of double bonds in unsaturated lipids, we investigated the effects of several edible antioxidants on these two molecular structural changes of double bonds in triolein (cis-9, 18:1) and trilinolein (cis-9, cis-12, 18:2), which were heated at 180 °C. trans Isomerisation and oxidative degradation of each cis double bond in the triacylglycerols during heating were evaluated on the basis of the increase in the amount of trans isomers and decrease in the amount of cis isomers by gas chromatography analysis. The synchronous suppression in trans isomerisation and cis deterioration of double bonds in these triacylglycerols were found by addition of antioxidants, whose inhibitory effects were associated with their kinds and concentrations. When triolein was heated in the presence of antioxidant, suppression of heat-induced trans isomerisation was directly proportional to that of cis deterioration. The results of our analysis suggested that the appropriate addition of antioxidants to edible oils during processing and cooking would facilitate the control of not only thermal oxidative degradation but also heat-induced trans isomerisation of double bonds in unsaturated lipids.