UC Davis

Carbohydrates comprise the largest fraction of most diets and play an integral role in human health. They exhibit immense structural diversity and have important biological functions that are dictated by these structures. However, current methods for the analysis of dietary carbohydrates bely these complex structure-function relationships. Typically, total carbohydrates are not even measured and those components that are measured—like dietary fiber and sugars, rely on crude gravimetric or liquid chromatography analyses that provide limited information. While methods based on gas chromatography-mass spectrometry (GC-MS) are commonly used for structural analysis of isolated plant cell walls, their limited throughput, sensitivity, and selectivity have prevented their widespread use for food analysis. This dissertation describes the development and application of liquid chromatography-tandem mass spectrometry (LC-MS/MS) based methods for food carbohydrate quantification and structural elucidation that directly address the inherent limitations of the GC-MS approach. Chapter 1 provides background on food carbohydrate structures and their importance in the context of the gut microbiome and host health. Chapter 2 provides a detailed protocol describing the details of these recently developed LC-MS/MS methods for the analysis of food and fecal biospecimens. Chapter 3 presents the application of these methods to create a detailed glycomic map of the maize plant that provides insight towards greater utilization of the entire plant. Chapter 4 describes the application of a rapid-throughput and quantitative monosaccharide analysis to determine the total monosaccharide compositions of over 800 foods to develop an open-access food carbohydrate database. Chapter 5 presents a novel workflow that applies a multi-glycomic analysis to isolated fiber fractions from existing methods for the determination of dietary fiber. The work presented in this dissertation highlights the importance and utility of these methods towards understanding how dietary carbohydrate structure impacts health through interaction with the gut microbiome.