Evaluating water activity and glass transition concepts for food stability

Water activity and glass transition temperature concepts were used to investigate the connection between the two distinct criteria of food stability. The data on sorption isotherms and glass transition temperatures were obtained from the literature. Two most commonly used models i.e. GAB and Gordon-Taylor equations were used to model water activity/moisture content and glass transition temperatures/solids content relationships. The models' (GAB and Gordon-Taylor) parameters were used to estimate water activity and glass transition temperature at given moisture/solids content. Results indicate that there is a considerable discrepancy in the temperature-related stability criteria predicted by the concepts of water activity (a_w) and the glass phenomenon (T_g). A greater understanding of water sorption properties and T_g is required to establish a sound processing and storage stability criteria.