GAB Generalized Equation for Sorption Phenomena

A generalization of the standard Guggenheim, Anderson, de Boer (GAB) equation is presented in this paper, which is based on the assumption that the parameter C of the GAB equation is not constant but rather some polynomial function of the water activity aw. Sorption data for wheat and potato starches were tested for the application of the generalized form of the GAB equation. It is shown that the standard GAB equation is adequate to describe experimental data for water activity values up to 0.90 but fails to adequately describe the experimental data when data in the range of aw 0.9–1.0 are included in the calculations. The generalized GAB form leads to successful description of the sorption data for water activity values from 0 to 1.