Water activity is defined as the current volume and availability of free water in a sample and 首ld not be directly compared with the water content (g water/ g substance). The water activity is given as the aw value and ranges between 0 (absolute dryness) and 1 (condensed humidity). Only this component takes an active part in the exchange with the ambient humidity and can possibly form the ideal medium for microbiological growth on the surface which influences the microbiological stability. The water activity also has an important effect on the chemical reactions in food. Novasina 水分活度儀 LabMaster