Vitamin Stability and Water-Solid Interactions
This dissertation investigates two major structure-function relationships important to food science: vitamin stability and water-solid interactions. Thiamine, vitamin B1, is an essential micronutrient in the human diet. While thiamine is found naturally and as a fortification supplement in many foods, it is chemically unstable on exposure to heat and some co-formulated ingredients, with degradation exacerbated in prolonged shelf-life products. The instability of thiamine is a concern for the development of dietary deficiencies, which are prevalent even in developed countries; however, thiamine stability is not widely studied in the food or pharmaceutical industries. Thiamine is commercially available in two salt forms: thiamine mononitrate (TMN) and thiamine chloride hydrochloride (TClHCl). This study focused on documenting the storage stability of thiamine in solution, considering the effects of which commercially available salt form of the vitamin was used, vitamin concentration, pH, and ions present in solution by monitoring chemical stability and degradation kinetics over a 6-month to 1-year period following storage at 25-80ºC, and expanded these studies into food systems (bread doughs). The results from these studies, including the reaction kinetics of thiamine degradation, the degradation pathway, and the sensory impacts of the degradation products formed, especially as affected by pH and food matrix, can be used to improve thiamine stability and delivery in foods.
The studies of water-solid interactions in this dissertation covered two topics: 1) the effects of formulating a variety of food-relevant additives on the crystallization tendency of amorphous sucrose; and 2) the effects of formulation on the moisture sorption behaviors and physical stability of spices, herbs, and seasoning blends. Sucrose lyophiles were co-formulated with a variety of additives and stored at 11-40% relative humidity (RH). The structural compatibility of sucrose with the additive, and related intermolecular interactions, dictated the tendency of the additive to either delay, prevent, or accelerate sucrose crystallization. Spices, herbs, and seasoning blends were exposed to increasing RH (23-75%) and temperature (20-50ºC) to determine the effect of storage and formulation on a variety of physical properties. In general, as complexity of blends increased, physical stability decreased. While this dissertation covers a wide variety of food chemistry and food materials science topics, including vitamin chemical stability, amorphous sucrose physical stability, and moisture sorption behaviors of spices, herbs, and seasoning blends, the findings provide valuable information on the chemical and physical stability of ingredient systems and how the structure-function relationships of the systems can be controlled for optimal ingredient functionality.