Characterization of the biochemical variability of bovine milk using metabolomics

Bovine milk contains a complex mixture of metabolites, which were identified by liquid and gas chromatography mass spectrometry methods. With the aid of new software methods, spectral assignment was carried out, enabling the identification of 223 metabolites. Those included amino acids, lipids, carbohydrates, nucleotides, energy metabolites, vitamins, cofactors and short peptides. Metabolite concentrations were compared between 10 bovine milk varieties, differing in brand, fat content, expiry date, package type and farming method. Principal components analysis showed a clear separation of the different milk varieties. Whole milk could be distinguished from reduced fat and fat free milk by higher lipid metabolites like free fatty acids, cholesterol and 1,2-dipalmitoylglycerol. But also, the reduced fat varieties had lower levels of vitamin E. In comparing organic to conventional milk, 14 named metabolites were statistically different between the two farming methods. This shows the potential of identifying farming-method-specific biomarkers upon analysis and validation of a larger sample size. Finally, high biochemical variability was shown in conventional whole milk derived from different producers. The distinct biochemical profiles of milk varieties shows the utility of metabolic profiling for authentication of milk varieties, and for deriving potential markers that can serve as signatures for a particular milk.