Determination of the molecular mobilty and oxygen permeability in amorphous protein films

In food systems, the amorphous solid is a metastable region subject to chemical, physical, and biological deterioration influenced by chemical structure and composition, environmental factors, and molecular mobility. Molecular mobility is thought to determine the rates of physiochemical changes occurring during food processing and storage. Temperature affects the motion of molecules, and therefore, the stability and quality of amorphous solids. To understand the events that occur at the macroscopic level in foods, we must first understand the events that take place at the molecular level. Phosphorescence can be used to monitor the distribution of molecular mobility and oxygen permeability in heterogeneous foods, providing the molecular detail necessary to connect food quality and stability to molecular structure, molecular mobility, and oxygen permeability. In initial studies, erythrosin B was embedded into model protein systems (BSA and gelatin), and phosphorescence techniques such as lifetime and emission energy were used to determine the molecular mobility and oxygen permeability as a function of temperature. Next, studies were performed on a more complicated model system of BSA and sugars, followed by a progression to the simple food systems of gelatin and dried collagen sausage casings. Finally, a method was developed to study actual sausages stuffed into erythrosin B doped collagen sausage casings via an external fiber optic coupler from the fluorescence spectrophotometer. The matrices studied showed a positive correlation between molecular mobility and oxygen permeability, and also, dynamic site heterogeneity. The addition of sucrose and trehalose to amorphous BSA films greatly reduced oxygen permeability. Gelatin showed a significantly lower molecular mobility (higher rigidity) as compared to BSA and collagen casings, and collagen casings were the least permeable to oxygen. Dried collagen casings became more heterogeneous and permeable to oxygen with aging. Measurements on sausages stuffed into erythrosin B doped casings demonstrated that this technique was very sensitive to oxygen quenching under different types of packaging and storage conditions. This was the first time phosphorescent techniques have been applied to actual food products in this manor, and future research will involve optimizing this technique by correlating the phosphorescent measurements to food quality and stability.Ph.D.Includes bibliographical references