LAUSR

Food is a multicomponent system that mainly comprises protein, carbohydrate, fat, and water. During food processing and preservation, various physical changes (e.g., melting, crystallization, glass transition) occur in food products, affecting their quality. This chapter specifically examines the effect of physical changes on the quality of dry and frozen food products. Dry food products are commonly in an amorphous state. Therefore, glass transition occurs during their dehydration-rehydration processing. To control their texture and physical stability, it is important to elucidate the effects of water contents on the glass transition temperature of dry food products. Frozen foods consist of ice crystals and freeze-concentrated matrix. The formation of ice crystal and the dynamics of ice crystal evolution affect food quality. Therefore control of ice crystals is important for high-quality frozen food. Moreover, because freeze-concentrated matrix consists of solute that are plasticized by the unfrozen water and is in an amorphous state, it can undergo glass transition by freeze concentration. The physical state of freeze-concentrated matrix also strongly affects the stability of food quality during frozen storage.