Moisture Sorption Isotherms of Red Chillies

The equilibrium moisture contents were determined for red chillies using the static method at 25, 35 and 45°C over a range of relative humidities from 0·115 to 0·865. The sorption capacity of chillies decreased with an increase in temperature at constant relative humidity. The sorption isotherms exhibited the phenomenon of hysteresis, in which the equilibrium moisture content was higher at a particular equilibrium relative humidity for desorption curve than for adsorption. Ten models were applied for analysing the experimental data. The equilibrium relative humidity of chillies can be predicted by using the modified Halsey and Kaleemullah models for adsorption process whereas the modified Oswin, Kaleemullah and Oswin models can be used for desorption process of chillies. As there was no common model to predict the equilibrium relative humidity of chillies during both the adsorption and desorption processes, the Kaleemullah model that was ranked second in both the adsorption and desorption processes for chillies can be considered and used with good predictive accuracy.