LIQUID CHROMATOGRAPHY TANDEM HIGH RESOLUTION MASS SPECTROMETRY AS AN ANALYTICAL METHOD FOR DAIRY METABOLOMICS

Abstract

Metabolomic analysis of dairy products by high-resolution mass spectrometry is a powerful technique to assess milk and dairy product quality. The small molecule signatures of milk and dairy products help to better understand milk quality, define how processing enhances health promoting components of dairy, and authenticate specialty cheeses. Mass spectrometry- based metabolomics research can easily be accomplished using liquid chromatography tandem high-resolution mass spectrometry (LC-MS). Based on a compound’s unique fragmentation pattern, metabolites detected by LC-MS in a sample can be rapidly identified by comparison to known spectral databases. Methods were developed to extract and analyze dairy products (milk, yogurt, cheese, butter fermented milk, sour cream, and dairy powders) based on their small molecule signatures using LC-MS. A total of 45 samples within the dairy categories were then analyzed using the established method. Cross-category and within-category dairy product molecular signatures were successfully differentiated from each other using principal component analysis and hierarchical cluster analysis. The method established in this thesis was then used to compare the molecular signatures of yogurt samples provided in two prior human intervention trials. Based on the presence of 595 detected metabolite signals and utilizing principal component analysis, hierarchical cluster analysis, and the relative abundance of individual compounds, this method illustrated distinct metabolomic differences on a whole-metabolome basis and a targeted-compound basis between the two different yogurts and provided potential insight into why they functioned differently.