Moisture Sorption Isotherms and Thermodynamic Characterisation of Averrhoa bilimbi (L.) Fruit

This study investigates the moisture sorption isotherms and thermodynamic properties of Averrhoa bilimbi (L.) fruit at the temperature of 25, 35, and 45°C using a gravimetric static method. The equilibrium moisture content (EMC) was measured under adsorption and desorption conditions, and five sorption models (GAB, BET, Peleg, Chung–Pfost, and Halsey) were applied to fit the experimental data. Among these, The BET model exhibited best predictive accuracy based on statistical parameters (R², χ², RMSE, and mean relative error). This study further evaluated critical water boundaries and calculated the net isosteric heat and sorption entropy using the Clausius– Clapeyron equation. Results demonstrated significant hysteresis between adsorption and desorption isotherms, with higher energy requirements during adsorption due to capillary condensation and bound water dynamics. The findings provide essential insights into the drying behaviour and stability of A. bilimbi, which can inform optimised postharvest processing and storage strategies for this highly perishable fruit.