ABSTRACT
Lipid oxidation is accepted as a free radical-mediated reaction. At low temperatures, hydroperoxides are the main products and catalysts of the reaction. Their catalytic effect results from their unimolecular and bimolecular decomposition to peroxyl and alkoxyl radicals. Although thermoxidation proceeds by the same basic mechanism as autoxidation, its rate is much higher and the quantitative nature of the reaction products is significantly different. This is because of the extreme instability of hydroperoxides and the lower solubility of oxygen in lipids at high temperatures. Consequently, there is an increased participation of alkyl and alkoxyl radicals and diminished participation of peroxyl radicals. Products of oxidation at high temperatures are mainly oligomers and polymers with carbon-carbon, epoxy, and ether bonds as opposed to the hydroperoxides formed at low temperatures.
