科研之友
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摘要
Understanding of the amorphous glassy state of food systems is often crucial in determining physicochemical characteristics and predicting stability of dehydrated and frozen foods. At the glass transition temperature (T-g) of food components, transformation from the amorphous glassy state to the liquid-like rubbery state occurs. T-g and ice-melting temperatures (T-m) of food systems are used to construct their state diagrams, in which the different physical states/phases and state/phase transitions of food components are presented in relation to temperature and concentration. A state diagram may be used to identify the appropriate processing and storage conditions of food systems. An overview of determination methods is carried out for glass transition temperature, ice-melting temperature and conditions of maximum-freeze-concentration (glass transition temperature of maximum-freeze-concentrated solution, T-g' and onset of ice-melting temperature, T-m') for food systems. The data as T-g, T-m, T-g' and T-m' are necessary for construction of state diagrams of foods. The advantages and limitations of the determination methods are discussed. Combined data for glass transition temperature, ice-melting temperature and conditions of maximum-freeze concentration for selected food systems are presented in this study. The effect of food composition on glass line, freezing/melting curve and maximum-freeze-concentration conditions is evaluated. The significance of the state diagrams in predicting the physical, chemical and microbial stability in foods is briefly examined. Glass transition concept and state diagrams are useful for describing the physical and structural stability of food systems at specific conditions, yet they are not considered as the only determining factors of chemical, biochemical and microbial stability of food systems.
- 出版日期2010-9
