Water activity and moisture sorption isotherms of foods

Moisture sorption isotherm is a valuable tool for food scientists and technologists because it can be used to predict potential changes in food stability. It can be used for storing method determination, packaging selection and ingredient selection. Moisture sorption isotherm of foods shows the equilibrium relationship between water activity and moisture content of the food at a constant temperature and pressure. A critical value of water activity also exists below which no microorganisms can grow. For most foodstuffs, it is in the range of 0.6 – 0.7. Generally, temperature has important influence on water activity and consequently on course of moisture sorption isotherms. By using the Clausius-Clapeyron equation, the dependence of water activity on temperature can be predicted.