Unsaturated fatty acids are easily affected by metal ions, leading to the changes of their flavor, nutrition, and safety through lipid oxidation. Nevertheless, there is a lack of comprehensive evaluation of the pro-oxidative ability of different metal ions, which have different effects on different lipids. Thus, in this work, crude lipids extracted from abalone were incubated with different metal ions, and the comprehensive lipid oxidation products were analyzed by nontargeted lipidomics approaches using an ultra-high-performance liquid chromatography-Q-Exactive HF-X Orbitrap Mass Spectrometer (UPLC-Q-Exactive HF-X). Results showed that the overall pro-oxidative ability from strong to weak was Fe3+, Fe2+, Cu2+, Zn2+, Mn2+, Mg2+, Na+, and K+. Among them, Fe3+ and Fe2+ could promote the accumulation of oxidation intermediates and branched fatty acid esters of hydroxy fatty acids. Na+, K+, Cu2+, and Mg2+ could accelerate the oxidation of N-acyl ethanolamines and ceramides. K+ and Na+ had more influences on the free fatty acids than Zn2+ and Mn2+. Slow oxidation of triglyceride may be attributed to its long distance from the oil-water interface and the restriction of the polar headgroups of phospholipids on free radicals.
Keywords: FAHFAs; UPLC-Q-Exactive HF-X; antioxidant; lipid structures; metal ions; pro-oxidative.