A BET approach to multilayer adsorption in swelling products

• A new generalized BET like equation is presented.
• The proposed equation is fitted to various experimental data of different foodstuffs.
• Good agreement between predicted values and experimental values is obtained.
• Obtained results are congruent with the development of a pore structure during sorption.

An equation for multimolecular sorption is presented. It is based on the BET model with the assumption that the adsorbing surface can be divided in two regions:A region that supports only a limited number of adsorbed layers due to geometric restrictions, and another region that can adsorb an unlimited number of layers. The proposed equation is applicable to type 2 and 3 isotherms (BDDT classification), and was successfully used to fit water sorption equilibrium data of some foodstuff from literature for the water activity range 0.05–0.90, and a temperature range from 10 to 70 °C.