Sorption isotherms and isosteric heats of sorption of mint variety (Mentha viridis) leaves and stems: Experimental and mathematical investigations

Knowledge of sorption isotherms of agricultural products is necessary to control rehydration/dehydration and storage processes. The aim of this work is to determine moisture adsorption and desorption isotherms of Moroccan mint leaves and stems ( Mentha viridis ). The sorption isotherms of the plants was determined within the range of 0.0549–0.964 relative air humidity at three different temperatures (40, 50 and 60 ∘ C) using saturated salt solutions method. Guggenheim, Anderson and Boer (GAB) model was used to describe the experimental data. The isosteric heats of desorption and adsorption were determined. Then, the isosteric heat of desorption was compared to the isosteric heat of adsorption and both decreased continuously with increasing the equilibrium moisture content. Finally, the comparison between the sorption net isosteric of mint leaves and stems was studied.