Glass Transition and Crystallization in Foods

The glass transition and crystallization are two of the major transitions in food which could affect the food physical properties significantly. The glass transition behavior and the crystallization phenomenon of food, as well as their interactions, are reviewed in this chapter. The major connection between glass transition and crystallization in a certain food or food component is the temperature. It has been reported that crystallization could hardly happen, if not impossible, below the glass transition temperature of food. And the temperature difference above or below the glass transition temperature (T - T_g) is an important indicator for food crystallization. Other factors, such as moisture content and molecular weight, also contribute to the interaction of glass transition and crystallization in foods. As examples the glass transition and crystallization of sugars, especially lactose and sucrose, which have been studied extensively in literature, are presented in this chapter. Other major food components are also summarized on their thermal transitions, including polyols, protein, and polysaccharides.