The moisture in a product is determined as the ratio of the mass of water that it contains and the mass of dry matter. This magnitude is called the specific moisture of the product.
When, in a fixed atmosphere, there is a product in which the partial pressure of water vapour is greater than that of the water vapour contained in the air, there is transfer of water vapour from the product to the air and so drying of the product.
This determines the sorption curves that express the thermodynamic equilibrium between the moist product and the surrounding atmosphere.
DESSICA dry air allows a very low partial pressure of water vapour to be obtained, allowing products to dry at low temperature (between 20 and 50°C) without deterioration in the intrinsic qualities of heat-sensitive products.