Tracking the dynamics of epoxy triglycerides during thermal oxidation by liquid chromatography-mass spectrometry

Epoxy triglycerides (ETGs) is a class of the most toxic component among the oxidized triglycerides (ox-TGs) in deep frying oil. To track the dynamics of ETGs during thermal oxidation, we developed an approach for qualitative analysis of ETGs by liquid chromatography-mass spectrometry (LC-MS). A total of 36 ETGs in thermal oxidized vegetable oil were identified as mono-ETGs, di-ETGs, tri-ETGs, hydroxyl-ETGs and aldehyde-ETGs by their characteristic fragmentations, such as precursor ions, diacylglycerols and oxidized mono-acylglycerol fragments. Furthermore, we evaluated the factors on the generation of ETGs. The results from vegetable oil system demonstrated that the total content of ETG was positively correlated with heating time, temperature and degree of unsaturation of oil (p < 0.05). Mono-ETGs in monounsaturated oil had an obvious increasing trend, while the proportion of hydroxyl-ETGs in polyunsaturated oil were much higher than other monomers. Taken together, our study suggested that ETGs could serve as the characteristic compounds to determine the degree of oxidation in vegetable oils.