Application of GAB model for water sorption isotherms of food products

The present investigation deals with analyzing the validity of GAB model for isotherms of different food products. The model was found satisfactory for different food products with different shapes of isotherms under widely varying conditions (temperature: 4-140C; moisture %D.B.: 2-71; activity: 0.059-0.99). The present study covered a wide range of food products from green vegetables, fruits, cereals and nuts to casein, pectin and protein. Food products with complex molecular struture and high sugar contents were also included. A non linear regression method was applied to evaluate the six parameters of the GAB model. The Guggenheim constant, factor for multilayer molecules and the monolayer moisture were assumed to follow an Arrhenius type relationship with temperature variation. The values of net isosteric heat of sorption obtained by GAB model and Clausius Clapeyron equation were compatible. Monolayer moisture values for food products obtained by GAB model were in agreement with values reported in the literature.