The regularity of heat-induced free radicals generation and transition of camellia oil

[Display omitted] •The hyperfine splitting constants (aN, aH) observed by ESR were adopted to identify free radical.•This study presents the range of hyperfine splitting constants (aN, aH) of alkyl, alkoxyl, oxygen-centered free radicals.•The transition pathway of alkyl free radical of camellia oil under heating process was revealed. In this study, the radicals formed in camellia oil upon a heating process were identified and quantified using Electron Spin Resonance (ESR) spectroscopy coupled with spin-trapping technique. PBN and DMPO were served as spin traps. The total amounts of free radicals of heated camellia oil showed an increasing trend with the extension of heating time at 140 °C, 150 °C and 160 °C. In accordance with hyperfine splitting constants (aN, aH) ─ the crucial parameter for identifying free radical species ─ of free radical, it was definitely confirmed that alkyl, alkoxyl, oxygen-centered and DMPO oxidate free radicals were present in heated camellia oil. A free radical transition pathway was proposed that alkyl free radical is initially generated, then, alkyl peroxy free radical is subsequently generated in the presence of oxygen which eventually shifts into alkoxyl free radical by means of an intermediate formed from H-capture reaction of alkyl peroxy free radical.