Food lipid analysis by GC-MS beyond fatty acid methyl esters

Abstract: The importance of lipids in nutrition, their applicability as authenticity marker and the adverse health effects of some lipid oxidation products makes the comprehensive analysis of lipids highly important in light of food safety and food quality. Due to the frequently highly complex lipid distributions in food, powerful analytical methods are required for their comprehensive characterization, identification and quantification. Particularly the hyphenation of mass spectrometry to liquid (LC-MS) or gas chromatography (GC-MS) enables to gather qualitative and quantitative information on a vast number of lipids at the same time. While GC-MS is most frequently used for the analysis of lower polarity and simple lipids such as fatty acids (as methyl esters) or sterols, the application of high temperature methods and specific chemical derivatization techniques can be used to assess the lipids and their structures in more detail.

Here, we present our results from the application of high temperature GC-QToF MS for the analysis of food lipids and the application of derivatization techniques for the analysis of chiral hydroxy fatty acids formed during lipid oxidation. Lipid extracts from 77 cereal samples from seven cereals and 16 milk samples (from cow, goat and sheep) were analysed by high temperature GC-QToF MS to access total lipid profiles including intact triacylglycerols. This enabled the sample groups in the cereal and milk samples, respectively, to be distinguished while, at the same time, important minor compounds could be profiled in the samples. In a second case study, we evaluate the GC-MS analysis of chiral hydroxy fatty acids, formed during lipid oxidation, as Mosher’s acid or ibuprofen esters, assessing the enantioselectivity of their formation and detect the contribution of enzymatic oxidation. These applications highlight the great potential of GC-MS beyond the common applications.