Program: Biomolecular Sciences PhD

Committee Chair: Owen McDougal

Committee: Owen McDougal, Henry Charlier, Loren Ward, Javier Ochoa-Repáraz

Abstact: Reliable quantification of fortified vitamins is necessary for evaluating nutrient retention, establishing formulation overages, and complying with labeling requirements. However, complex food matrices and protective coatings can limit vitamin extraction and lead to inaccurate quantification. This dissertation investigated how dairy matrix composition, storage-induced changes, and ethyl cellulose (EC) encapsulation affect the quantification of water-soluble vitamins.Extraction methods were developed for vitamins C and B5 in whey protein concentrate (WPC), ready-to-mix (RTM) drinks, and whey protein isolate (WPI). Vitamin C and B5 are often used to fortify foods due to their antioxidant protection and role in coenzyme A for energy production. Vitamin recoveries were 95-96.5% from WPC, 77-86% from RTM, and 62.5-64% from WPI, demonstrating that protein content, matrix composition, and vitamin-protein interactions influenced extractability. An accelerated shelf life study evaluated vitamins C and B5 in RTM and WPI powders stored at 25, 35, and 45°C in the presence and absence of oxygen. Through 16 weeks, both vitamins followed first-order kinetics under nitrogen-flushed conditions. In non-flushed samples, vitamin C followed zero-order kinetics, whereas vitamin B5 exhibited matrix- and temperature-dependent zero- or first-order behavior. Degradation depended on matrix rather than temperature. After 16 weeks, measured vitamin concentrations increased. Fluorescence, melting temperature, particle size, and zeta potential measurements showed no protein aggregation or denaturation, suggesting that storage altered vitamin-protein interactions and accessibility to the extraction solvent, thereby increasing recovery. Methods were evaluated for quantifying EC-coated vitamins C, B5, and B9. Vitamins C, B5, and B9 were chosen as representative vitamins that degrade during processing and storage and are all available in encapsulated forms. Compared with the industry-standard boiling method, liquid-liquid extraction (LLE) reduced sample preparation time by approximately 50%, increased recoveries of vitamins C and B9 by approximately 20%, and improved reproducibility. Near-infrared spectroscopy coupled with chemometric modeling enabled rapid, nondestructive quantification without removing the EC coating, with coefficients of determination of at least 0.984. Overall, this work demonstrates that matrix composition, storage-induced structural changes, and encapsulation influence both vitamin stability and analytical recovery. The resulting extraction and spectroscopic approaches provide improved tools for formulation, shelf life assessment, and regulatory analysis of fortified food products.

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