UHPLC/MS analysis of triacylglycerols in edible oils and animal fats and application in the detection of food fraud

Abstract

A novel direct method using ultra-performance liquid chromatography, developed by Chanidou (2020), coupled with ion trap mass spectrometry, was established for the discrimination of commercial edible oils and animal fats based on TAG analysis. The application of this lower-cost combination was evaluated and validated using a wider range of commercial edible oils and animal fats than in the original study. The UHPLC method has advantages over previous methods of improved resolution and speed. Statistical analysis of the dataset using principal component analysis (PCA) and hierarchical cluster analysis (HCA) was accomplished to determine the extent to which oils from twelve various plant sources and eight different animal fats could be distinguished by their TAG distributions. The combination of UHPLC-APCI MS and chemometrics tools (PCA and HCA) has been shown to give reliable discrimination of various edible oils and animal fats using this rapid and relatively low-cost combination. Mixtures of the high-value oils, olive and sesame, with lower-cost oils, were examined as representative of adulteration of these oils and shown to be distinguishable from the pure oils, even in mixtures of oils with quite similar major TAG compositions. Sensitivity to post-production alteration was evaluated using a selection of aged and degraded oils. It was illustrated in PCA that after long-term storage, some oil samples, especially polyunsaturated oils (e.g. sunflower, corn and rice bran), no longer clustered with their original fresh oils’ counterparts, indicating that a change in their TAG profiles occurred. By contrast, the clustering of olive and sesame oils was largely unaffected, indicating them to be much more stable during long-term storage. The discrimination of heated oils from fresh oils was examined; the combination of PCA and HCA revealed that sunflower samples were more stable than olive samples under cooking conditions. Hence, this fast, simple, robust and reliable method offers significant benefits in authenticating edible oils, evaluating oil degradation, and differentiating meat products from their fats. The method has excellent potential for universal use.