Applications Of Chemometrics In Studying The Influences Of Genetic Variation And Processing On The Chemical Composition Of Foods

Abstract

Genetic variation is an essential internal factor while processing is a common external factor that determines the chemical composition of food. Characterization of chemical changes from genetic variation and processing is a challenging but also important task in monitoring the organoleptic, nutritional, and safety properties of food. This thesis study examined the efficacy of liquid chromatography-mass spectrometry (LC-MS)-based chemometric analysis in defining the chemical features associated with genetic variation and processing through two case studies on wild rice and mesquite flour, respectively. Wild rice (Zizania spp.), an ancient grain revered by Native Americans, has a more desirable nutritional profile in comparison with Asian rice. However, the differences between the lipidome of wild rice and Asian rice has not been well examined. In this study, the LC-MS-based untargeted profiling was performed on the lipid extracts from wild rice, white rice, and brown rice. Triacylglycerols (TAG) rich in essential fatty acids α-linolenic acid (ALA) and linoleic acid (LA) and the steradienes from phytosterol dehydration emerged as the primary features that separate wild rice from Asian rice. The phytosterol content of wild rice was further analyzed through the quantification of γ-oryzanol and stigmasterol, illustrating the enrichment of these phytosterols in wild rice. The presence of steradienes in wild rice is attributed to its unique processing after harvesting. Chemical influences of processing were investigated by conducting the LC-MS-based chemometric analysis of the mesquite flour (Prosopis spp.) treated with intense-pulsed light (IPL), a novel non-thermal disinfection processing that is compatible with powdered food. Targeted analysis of acetic acid and propionic acid, two flavor compounds, showed that the influences of IPL on the concentration of these two short-chain fatty acids were comparable to the effects of γ-irradiation, another non-thermal disinfection method. The untargeted analysis showed that IPL increased 9-hydroyoctadecadienoic acid (HODE), a lipid oxidation product, as well as α-ketoisovaleric acid, a degradation product of amino acids. Overall, LC-MS-based chemometric analysis proved to be a powerful tool in assessing the alterations in food due to genetic variation and processing.