Guggenheim-Anderson-deBoer model

Sorption isotherms of model systems were determined gravimetrically and data were modeled using the Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-deBoer (GAB) models. 

The Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-deBoer (GAB) sorption isotherm models were used to obtain experimental steady-state moisture contents in dry basis by linear regression analysis according to Kouassi and Roos (2002). These equations provide the value of monolayer water content, which is an important parameter in food deterioration studies. 

For most practical purposes, the isotherm can be modeled by an empirical (Brunauer, Emmett and Teller BET) or theoretical (Guggenheim, Anderson, and DeBoer GAB) equation (see below) however, none of the isotherm models in the literature is valid over the entire aw range of 0 to 1. The GAB model is one of the most widely accepted models for foods over a wide range of aw (from 0.10 to 0.90). The details of the different isotherm models with their parameters have been compiled by Rahman (1995). The BET (Eq. A2.3.4) and GAB (Eq. A2.3.5) equations are given as follows ... 

Water vapor adsorption isotherms have been obtained on cotton from room temperature up to 150°C [303,304]. Theoretical models for explaining the water vapor sorption isotherms of cellulose have been reviewed [303]. Only adsorption theories will be discussed here at ambient temperatures. The shape of the isotherm indicates that multilayer adsorption occurs and thus the Brunauer, Emmett and Teller (BET) or the Guggenheim, Anderson and deBoer (GAB) theory can be applied. In fact, the BET equation can only be applied at relative vapor pressures (RVPs) below 0.5 and after modification up to a RVP of 0.8 [305]. The GAB equation, which was not discussed in the chapter in the book Cellulose Chemistry and Its Applications [303], can be applied up to RVPs above 0.9 [306]. Initially as the RVP... 

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