Food stability beyond water activity and glass transtion: Macro-micro region concept in the state diagram

The water activity concept proposed that a food product is the most stable at its monolayer moisture content. Recently, the limitations of the water activity concept were identified and the glass transition concept was proposed in order to overcome the limitations of water activity. Based on the glass-transition concept, a food is the most stable at and below its glass transition point. Recently it has also become evident that the glass transition concept is not universally valid for stability determination when foods are stored under different conditions. The glass transition concept was used to develop the state diagram by drawing another stability map using freezing curve and glass line. Currently, other components indicating different characteristics are being included in the state diagram. It is being emphasized in the literature to combine the water activity and glass transition concepts. In this paper, an attempt is made to combine these two concepts in the state diagram and to propose a macro-micro region concept for determining the stability of foods.