Equilibrium Moisture Isotherms for Mate Leaves

An experimental study to obtain the equilibrium moisture content (EMC) of mate leaves (Ilex paraguariensis) in a desorption process was carried out at different relative humidities and temperatures. Saturated salt solutions were used to control the humidity of the air in equilibrium with the samples of mate leaves. All the vessels containing the saturated salt solutions and the particles of mate were taken into an oven at controlled temperatures of 30, 40 and 50 °C, respectively. Measurements of mate moisture content were periodically performed up to the equilibrium between the concentration of water in the fluid phase and its concentration in the desorbent particle. Replications were carried out in order to verify the consistency of the experimental procedure. A comparison between the experimental data obtained in this work and those reported in the literature corroborates the experiments. A statistical analysis of the experimental results confirms the effect of both the variables on EMC. Five different empirical expressions and one semi-empirical model correlating the experimental EMC data to the relative humidity and temperature of air were proposed. A regression analysis indicates the Modified Halsey model as the best among the models investigated.