Evaluation on the formation of lipid free radicals in the oxidation process of peanut oil

Oil oxidation is considered to involve the formation of free radicals. In this study, several major fatty acids in peanut oil have been investigated, and it showed that free radicals were mainly generated from the unsaturated fatty acids oleic acid and linoleic acid. Through a fitting analysis of the types of free radicals, they were identified as alkyl peroxy radicals (DMPO-center dot OOL), alkoxyl radicals (DMPO-center dot OL), alkyl radicals (DMPO-center dot L), and unknown radicals (DMPO-center dot X). In a comparison of two different heating temperatures, at 90 degrees C the electron spin resonance (ESR) spectrum was dominated by alkoxyl radicals (DMPO-center dot OL) and an unknown radical (hyperfine splitting constants of alpha(N) = 14.73 G and alpha(H) = 2.12 G, as befits a comprehensive carbon-centered radical). At 120 degrees C, the ESR spectrum was dominated by alkyl radicals (DMPO-center dot L). This study has indicated that ESR provides a powerful method for evaluating free radical generation in the oxidation of peanut oil.