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-•OOL), alkoxyl radicals (DMPO-•OL), alkyl radicals (DMPO-•L), and unknown radicals (DMPO-•X). In a comparison of two different heating temperatures, at 90 °C the electron spin resonance (ESR) spectrum was dominated by alkoxyl radicals (DMPO-•OL) and an unknown radical (hyperfine splitting constants of αN = 14.73 G and αH = 2.12 G, as befits a comprehensive carbon-centered radical). At 120 °C, the ESR spectrum was dominated by alkyl radicals (DMPO-•L). This study has indicated that ESR provides a powerful method for evaluating free radical generation in the oxidation of peanut oil.