Unveiling the Antioxidant Mechanism of Canolol: Packaging Impacts the Long-Term Stability of Microwave-Pretreated Rapeseed Oil

Canolol is a pivotal phenolic antioxidant in rapeseed oil, yet its specific antioxidant mechanism and stability determinants during storage remain poorly understood. This study elucidates the antioxidant pathway of canolol within a lipid autoxidation model and evaluates its stability during the 52-week storage (25 ± 2 °C) of microwave-pretreated rapeseeds under varying packaging conditions. Rapeseeds were packaged in polyamide/polyethylene (PA/PE) vacuum bags and polypropylene (PP) atmospheric bags, and then monitored for seed quality, oil oxidative indices, and micronutrient contents. Via high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (HPLC-Q-TOF/MS/MS), a canolol-derived dimeric oxidation product (C20H24O7, m/z 375.1437) was tentatively identified in an 2,2’-azobis(isobutyronitrile) (AIBN)-initiated ethyl linoleate (EtL) autoxidation system. The MS/MS fragmentation pattern—characterized by neutral H2O loss, sequential •CH3 eliminations, and syringyl-type diagnostic ions—supports a mechanism involving hydrogen atom transfer (HAT) from canolol to lipid-derived peroxyl radicals. This is followed by the oxidative cross-coupling of a canolol-derived phenoxyl radical (ArO•) with a hydroxyethylated intermediate (Ar′O•), confirming canolol’s role as a chain-breaking antioxidant. Correlation analyses confirmed canolol as the primary antioxidant (r = −0.914, −0.984/−0.959, −0.883 with acid value/peroxide value, p < 0.01), with a synergistic effect relationship with tocopherols (r = 0.878, 0.966, p < 0.01). PA/PE vacuum packaging (low oxygen permeability) significantly mitigated canolol degradation (22.41% loss vs. 76.34% in PP), reducing tocopherol loss and oil oxidation. This study clarifies canolol’s antioxidant pathway in rapeseed oil, providing theoretical insights for phenolic antioxidant research and practical packaging guidance for the edible oil industry.