Mathematical modelling of water sorption isotherms and thermodynamic properties of Cucumis melo L. seeds

Moisture sorption isotherms for Cucumis melo L. seeds are determined at different temperatures of 30, 40 and 60 degrees C with the standard gravimetric-static method. The isotherm curves exhibited a type II behavior according to BET classification. For desorption and adsorption isotherms, equilibrium moisture content decreases with increasing of temperature at constant water activity. Moreover, the sorption isotherms exhibit hysteresis effect. Several models were applied to fit the relationship between equilibrium moisture content and the environment conditions data for melon seeds. The results examination indicates that Peleg model is able to reproduce experimental data within an acceptable precision. Additionally, sorption isotherms data were used to determine the thermodynamic properties such as net isosteric heat of sorption which was evaluated through direct use of moisture isotherms by applying the Clausius-Clapeyron equation. Increase in the equilibrium moisture content generated the decrease of net isosteric heat of sorption. As well, microscopic analysis shows a significant effect of desorption/adsorption process on microstructure of the seed.