For food products, the sorption isotherm can be measured by means of three different measuring techniques: gravimetric, manometric or hygrometric, according to Iglesias and Chirife, 1978 (21). In the gravimetric methods, the weight of the sample is measured with a balance.

A water vapor sorption isotherm is a measure of water content as a function of relative pressure (P/P₀) for pure water measurements or relative humidity (RH), when water is entrained in another gas.

Water sorption and solubility was calculated: 1. Sorption (mg/cm2) = (W2−W1)/Surface area 2. Solubility (mg/cm2) = (W1−W3)/Surface area.

Silica gel exhibits an excellent capacity for adsorption of water up to 35–40% of its dry mass at conditions found in chillers and hence, chosen as the adsorbent for our experiment.