Moisture adsorption characteristics of solar-dried mango slices

Moisture adsorption isotherms of solar-dried mango slices (cv. Kitchener) were determined at three temperatures (20°C, 30°C and 40°C) for a water activity (aw) range of 0.111 to 0.813 using the standard static gravimetric method. The sorption characteristic of solar-dried mango slices followed type III (J-shaped) isotherms, characteristic of high sugar products. An intersection of the curves occurred at a^w=0.75 for the investigated temperatures, which indicates the occurrence of the reverse temperature effect. The experimental equilibrium moisture content data were subsequently fitted to two well-known mathematical sorption models; namely, the BET and GAB models. Non-linear regression analysis was used to evaluate the models’ parameters. The validation of the two selected models was done by using statistical parameters: the mean relative percentage deviation (% P) and the coefficient of determination (R²). The estimated parameters of the GAB model were correlated to temperature. The (K) parameter of GAB model was found to increase with temperature, whereas the monolayer moisture content (Mo) decreased with increasing temperature. The Arrhenius-type relationships of the GAB parameters were determined. The GAB model was satisfactorily used to predict the equilibrium moisture content (EMC) of solar dried-mango slices.