Epoxy fatty acids in triacylglycerols: Elucidating the influences of oxidation conditions and lipid structures on formation and accumulation during lipid oxidation to enable their precise analysis in food

• Applicant: Professor Dr. Simon Hammann
• Subject Area: Food Chemistry
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 520944998

Lipid oxidation in food frequently comes with quality loss, as nutritionally valuable lipids such as polyunsaturated fatty acids can be lost in the process. In addition, there are implications for food safety since some lipid oxidation products have unfavorable bioactivities and are undesired in food. Amongst these, epoxy fatty acids are one of the most important secondary lipid oxidation products, also from a quantitative point of view. In food, they are usually occurring esterified to triacylglycerol as an epoxy-modified fatty acid chain. Due to the high structural complexity of the oxidized lipid fraction in food and largely absent experimental reference data the analysis of epoxy modified triacylglycerol still comes with significant challenges. Therefore, the (quantitative) analysis of epoxy fatty acids is by and large achieved on the fatty acid level after liberation of the epoxy fatty acid chains from the glycerol backbones instead. However, in this process important structural information (for example about the position of the epoxy fatty acid on the glycerol backbone), with importance to understand bioactivities, formation and hence mitigation strategies, are lost. The goal of this project is to elucidate the impact of oxidation conditions and lipid structures on the formation and accumulation of triacylglycerol-bound epoxy fatty acids and, together with newly acquired experimental reference data, achieve a structurally refined analysis of these compounds in food. For this purpose, >40 epoxy-modified triacylglycerols will by synthesized and characterized thoroughly by chromatography, mass spectrometry and NMR spectroscopy (Aim 1). In extensive incubation experiments with oxidation-susceptible reference triacylglycerols, under conditions favouring autoxidation or photooxygenation, the impact of different oxidation conditions on the formation and accumulation of epoxy modifications will be investigated. Furthermore, by employing structurally different triacylglycerols in these experiments, e.g., with the labile fatty acid chain esterified to the outer sn-1/3 or the inner sn-2 position of the triacylglycerol, the impact of lipid structures will be assessed as well and the principal formation mechanism of the epoxy modification in different conditions elucidated (Aim 2). Finally, using the data from reference compound synthesis and incubation experiments we will analyse epoxy-modified triacylglycerols and evaluate the patterns in a set of lipid rich food items (Aim 3). This project will provide the research community with the required reference data for analysis of epoxy-modified triacylglycerols and will significantly improve our understanding about these compounds and their analysis in food.

• DFG Programme: Research Grants