Unsaturated oils degrade rapidly at frying temperatures. Stabilization approaches based on free radical chain reactions have had limited success, so it is clear some reaction mechanisms are not being considered. To elucidate reactions involved in thermal degradation of lipids, a corn oil-high oleic acid sunflower oil blend was heated in an Oxipres� oxygen bomb at temperatures from 100 to 180 �C under 2 bars air for up to three hours. The headspace was vented through a thermal desorption trap and volatiles were analyzed by gas chromatography; oils were analyzed for conjugated dienes, hydroperoxides, aldehydes, and free fatty acids. Results support thermal scissions described by Nawar (Food Chemistry, Fennema, 1986) as the dominant degradative process at high temperatures. Thermal scission radicals add oxygen to form peroxyl radicals that initiate autoxidation chains, which increase in importance as heating is prolonged. A reaction scheme integrating thermal scissions, autoxidation, and heating conditions is proposed.

Degradation of lipids at high temperatures: Thermal scission vs. accelerated autoxidation

246th National Meeting (2013)

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