Effect of temperature on moisture sorption isotherm characteristics of Thai jasmine paddy (Khao Dawk Mali 105)

Mathematical models of moisture sorption isotherms were evaluated to assess their suitability for long grain paddy (Khao Dawk Mali 105) across various temperature ranges. Paddy samples were placed in sealed containers with relative humidity controlled, ranging from 5.32% to 84.34%, and temperatures maintained from 25 to 70 ° C , until equilibrium between the samples and the container's atmosphere was reached. Results showed that for both desorption and adsorption isotherms, equilibrium moisture content (EMC) decreases with an increase in temperature at constant water activity. However, at constant temperature, when water activity increases, EMC also increases. Additionally, the sorption isotherms exhibit a hysteresis effect. At 25 °C, the Henderson model proved to be the most suitable. At 40 °C, the Chung and Pfost model was best suited for adsorption, while the Henderson model was optimal for desorption. At 60 °C, the Peleg model was the most appropriate for adsorption, and the Henderson model remained the most suitable for desorption. At 70 °C, the Peleg model was the most suitable for both adsorption and desorption. The application of mathematical modeling to predict the EMC of jasmine rice at various temperature and relative humidity levels is crucial for efficient storage and processing planning within the rice export industry. • The use of a closed-container with saturated salt solutions to determine the sorption isotherms of jasmine paddy. The temperatures ranged from 25 to 70 °C, encompassing the range from room temperature to drying temperatures. Jasmine rice is a major export product of South Asia and Southeast Asia. Knowing the mathematical equation of equilibrium moisture will be highly beneficial for research on storage and postharvest technology.