Moisture adsorption isotherm study of dried Cassia alata was evaluated in this work. Adsorption isotherm of dried C. alata was determined at three different temperatures (10, 30 and 40 °C) and at six levels of relative humidity (ranging from 23 to 87%) using a gravimetric technique. The sorption isotherms were found to be typical type II sigmoid. The experimental data obtained was fitted to several mathematical models viz. two-parameter (BET, Oswin, Smith, Caurie, and Iglesias and Chirife), and three-parameter (GAB) relationships. Standard statistical procedures were applied to deduce percent error (P), root mean square error (RMSE) and coefficient of relation (r2). In terms of the mean absolute percentage error (P) of the fits, those with less than 10% error can be considered acceptable and an r2 of >0.98 may also indicate a good fit. The Peleg followed by Iglesias and Chirife model were found to best fit the experimental data.

Abstract. Cassia alata plant has been commonly used as medicinal herbs for treating fungal infection such as ringworm and eczema. Nevertheless, a few studies on drying characteristics have focused on C. alata. This work aims to investigate the drying characteristics of C. alata leaves at different temperatures. Moreover, the effects of different drying temperatures on colour qualities of C. alata leaves had been determined. The leaves were dried at different temperatures (40, 50, 60, 70, 80 and 90 °C) using a laboratory oven. Dried and fresh leaves were analyzed for the moisture content and colour analysis. The EMC of C. alata leaves decreased from 0.30 to 0.10 g water/dry matter as the temperature increased from 40 °C to 90 °C. The colour qualities of C. alata leaves were lower with increasing drying temperature.

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