ABSTRACT
The moisture sorption isotherm could predict that water bonds strongly to the polar sites of a food matrix. The higher the water activity, the faster the reaction rate because of the greater solubility and increased mobility of the reactants. The bond energy of the adsorbed water would inhibit interactions between polar groups on adjacent carbohydrate or protein molecules and thereby preserve rehydration ability, reconstitution ability, and texture of foods. The browning reaction rate increases from water activity at the Brunauer–Emme–Teller monolayer, sharply increases to a maximum, and then decreases. Enzyme-catalyzed reactions can proceed in foods with relatively low water contents. The nutrition loss of dehydrated foods depends on the storage temperature, light, oxygen, and water activity. The microbial response may differ at a particular water activity when the latter is obtained with different solutes. The water activity concept is mainly based on the binding nature of water and its relationships with the food stability or reactivity.
