Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for small molecule analysis in foods

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a promising analytical tool in food science due to its speed, ease of sample preparation, ability to analyze complex mixtures, and simplicity of mass spectral interpretation. This thesis explores several qualitative and quantitative applications of MALDI-TOF MS in food science, focusing on key phytochemicals, polymers, and emulsifiers. Specifically, important conditions such as sample preparation, selection of matrices, use of internal standards, and determination of response factors are investigated for ginsenosides, hydrogenated starch hydrolysates, polysorbate emulsifiers, and flavonol glycosides.; A simple MALDI-TOF MS protocol to analyze ginsenosides in American ginseng root powder was evaluated by comparison with thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). Ginsenosides in the biological ginseng system could not be readily analyzed by MALDI-TOF MS in that a simple purification step to separate ginsenosides from interfering substances was not achieved, mass spectra were of variable quality, and not all ginsenosides could be detected and differentiated by mass.; The composition of hydrogenated starch hydrolysates was investigated using MALDI-TOF MS. Oligomers spanning 1 to 28 units were identified, and differences in the degree of hydrolysis of a low, medium, and high maltitol syrup were observed. Spectrum-to-spectrum variability, lack of high mass standards, and mass discrimination limited the ability to quantify these polymers.; The molecular composition of polysorbate emulsifiers was studied. MALDI-TOF MS analysis before and after saponification indicated the presence of free ethylene oxide polymers, as well as free and esterified sorbitan- and sorbide-based polymers. This analysis also provided insight into the polydispersity, degree of esterification, and identity of esterified fatty acids.; Four flavonol glycosides in almond seedcoats, isorhamnetin rutinoside, isorhamnetin glucoside, kaemferol rutinoside, and kaempferol glucoside, were rapidly identified and quantified by MALDI-TOF MS. An internal standard, rutin (quercetin-3-rutinoside), was employed. Results of MALDI-TOF MS analysis were verified by HPLC. In addition, seedcoats of sixteen almond varieties were screened for flavonol glycosides. Individual peak ratios were consistent across triplicate analyses of all samples. In all almond varieties, isorhamnetin rutinoside was most abundant, and the total flavonol glycoside content ranged from 75 to 250 μg per gram of seedcoat.