Development of an LC-MS/MS method for the analysis of triacylglycerols from meat and application in the discrimination of cooked meat products

A single stage reversed phase high performance liquid chromatography (RP HPLC) separation of animal fat triacylglycerols (TAGs) has been developed for coupling with atmospheric pressure chemical ionization tandem mass spectrometry using an ion trap mass spectrometer. The method developed offers significant improvements on existing methods for TAG analysis, giving better resolution of TAGs with similar equivalent carbon number (ECN), and good separation of TAGs with odd ECN and TAG regioisomers of animal fats. Although the analysis times for chromatographic analysis of these TAGs are long, this is compensated by better separation of highly unsaturated TAGs. Development of an ultra high performance liquid chromatography method has reduced the run time by half, while maintaining separation and resolution. The TAG profiles of fats reflect their fatty acid (FA) compositions, showing a high proportion of unsaturated FAs for chicken and pork, whereas, saturated FAs are dominant in the major TAGs detected in beef and lamb. The improved RP HPLC separation of TAGs developed in this study has been shown to give more reliable discrimination of different animal species than previous methods including analysis of FAs as the methyl esters and RP HPLC separations of intact TAGs. All animal species separated well in the principal component analysis (PCA) plot of TAG profiles, whereas in the PCA plot of FA, chicken plots very close to pork fat, particularly ham. The profiles of TAGs in animal species highlight a number of components that are important for species discrimination.

The meat products of different species (beef, pork, chicken and lamb) cooked by microwave, roasting and currying are separated well in the PCA scores plot. This work shows that the discrimination of meat from different animal species is possible for both raw and cooked meat products, and reveals that the differences produced by the various cooking methods were less than the variations observed between species. The loadings values for the scores plot of TAGs for raw and cooked meat products are similar to the raw meat in different animal species and have the same important descriptors for discrimination. Hence, analysis of intact TAGs in cooked food products has considerable potential for detection of adulteration of cooked meat-based food products.