Drying Equilibrium

Drying slows as the difference between product water activity and environmental equilibrium decreases. At equilibrium, molecular exchange continues even though net mass change is small.

The equilibrium moisture content changes with temperature, relative humidity and product composition. Moving the same product to another environment can restart gain or loss.

A product reached by drying can behave differently from one reached by moisture uptake. Processing history, structure, salt and fat affect the sorption path.

A flat weight curve may indicate equilibrium, limited transfer, packaging effects or a measurement problem. It does not by itself establish uniform internal moisture.

Water activity is the relevant thermodynamic measure for microbial water availability. Moisture content and chamber humidity are supporting variables, not universal substitutes.

Define the intended product endpoint, measurement method and storage environment. Verify representative internal condition rather than extending drying until weight merely stops changing.