Abstract—The moisture sorption isotherms of Clinacanthus nutans (C. nutans) herbal leaves were established at three different temperatures of 30°C, 40°C, and 50°C, and water activity between 0.3–0.9 using a static gravimetric method. The results showed that equilibrium moisture content of C. nutans increased with increasing water activity at a constant temperature for both desorption and adsorption isotherms. In contrast, the equilibrium moisture content decreased when the temperature increased at a constant water activity for all isotherms. The sorption isotherms exhibited Type III behaviour or J-shaped curve according to Brunauer-Emmett-Teller (BET) classification. It was found that Guggenheim-Anderson-de Boer (GAB) and Peleg models were the best-fit to the experimental moisture isotherms. The maximum net isosteric heat of sorption values were found to be 70 kJ/mol and 13 kJ/mol for desorption and adsorption respectively. The moisture sorption isotherms established are essential for optimum design of C. nutans dryer and storage conditions.

Keywords—C. nutans, herb, sorption isotherm, monolayer moisture content, net isosteric sorption heat

Cite: Sriyana Abdullah, Yus Aniza Yusof, Nor Nadiah Abdul Karim Shah, Faiqa Shazeaa Mohd Salleh, Muhammad Azhar Ali, and Norawanis Abdul Razak, "Moisture Sorption Isotherm of C. nutans Herbal Leaves," Journal of Advanced Agricultural Technologies, Vol. 10, No. 1, pp. 8-15, June 2023.

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