Concept of water content & water activity

The water activity concept came into common usage in the 1970s, gaining official recognition with its incorporation into Community regulations, with a special focus on meat products. It adds a thermodynamic (ability to react and diffuse) qualitative property to the concept of water quantity, but can still be used to identify, for instance, a product’s storability, given the wide range of mechanisms brought into play by all the constituents that are not necessarily in a state of equilibrium.