Mechanism of methyl elaidate on the thermal oxidation behavior

The effects of cis-trans isomerization on the oxidation products of oleic acid (composites and structure characterization) were investigated. The reduction of thermal oxidation reaction of methyl elaidate (ME) was 6.72 % lower than that of methyl oleate (MO), and the oxidation products (core aldehydes) first increased and then decreased with the prolongation of thermal oxidation time. ME exhibited better oxidation stability than MO in free radicals, hydroperoxides, double bonds, aldehydes, and glycerides. The oxidation products were mainly 11-oxo-9-undecenoate (initial stage) and methyl 9-oxononanoate (later stage), following the free radical chain reaction mechanism. The H8 in double bond was more easily dehydrogenated in the chain initiation stage than H11, followed by the formation of core aldehyde through three intermediates and two transition states each pathway. ME required a higher energy barrier (1.3-13.6 kJ/mol) than MO reaction, making it more difficult for ME to undergo thermal oxidation reaction. The transition state 4 and 5 were rate determining steps of chain initiation reaction and proliferation reaction, respectively. This study was of great significance to further control the formation of these trans fats and their oxidation products.