Can rerouting of alkoxyl radicals from hydrogen abstraction/chain propagation to rearrangement to epoxides in oxidizing methyl oleate explain apparent low oxidation of monounsaturates?

The food industry has focused on monounsaturated oils due to perceived health benefits and stronger resistance to lipid oxidation assumed from slow, low production of hydroperoxides and certain aldehydes. In contradiction to this pattern, we previously observed epoxides as the first and major products of oxidized methyl oleate (MO) while lipid alcohol (LOH) concentrations remained very low throughout the oxidation. As LOH are key products of free radical chain propagation, this observation raised the possibility that alkoxyl radicals may be rerouted from H abstraction to rearrangement to slow apparent oxidation in monounsaturated oils.
To comprehensively study LOH formation and decomposition, MO was incubated at three different temperatures for up to 60 days, with 2 replicates withdrawn for analysis every 3 days. To increase LOH detection, we used a CP-Sil88 for FAME column and silylated HO groups in oxidized MO using BSTFA with 1% TMCS. All products were analyzed using Gas Chromatography with Flame Ionization Detection, as well as High-Performance Liquid Chromatography. Compounds were identified by mass spectrometry and chemical standards. To address the challenge of silylation requiring high temperatures that may lead to lipid thermal degradation, various silylation conditions were evaluated, culminating in the proposal of an optimal silylation procedure.
Alcohol concentrations were low for all 3 temperatures in comparison to aldehydes and epoxides, and typical scission products like octanols and nonanols were not detected. On the other hand, unknown alcohols especially with longer retention times were observed yet not identified. Again, dominant products were epoxides and their derivatives, supporting the hypothesis of a shift from hydrogen abstraction to internal cyclization of alkoxyl radicals in MO. These findings challenge traditional oxidation pathways, may partially explain low apparent oxidation rates of monounsaturated oils, and argue for analysis of epoxides in high oleic, if not all, oxidized oils.