Estimation of Moisture Sorption Isotherms of Date and a Determination of the Most Appropriate Model



In this research, moisture sorptions of Sayer date were determined at 20, 30, 40 and 60°C, using the standard static gravimetric method developed by the European Cooperation project Cost 90. Several mathematical models, namely GAB, BET, Iglesias & Chirif and Halsey were employed to fit the experimental data through non-linear regression. Results indicate that equilibrium moisture content increases with water activity. The overall shape of the curves describing the moisture content as function of water activity was typical of sugar-rich material. It was found that the Iglesias & Chirif and GAB models (for all the temperatures) satisfactorily fitted the sorption data. In addition, Isosteric heat of sorption was determined from sorption data, using the Clausius-Clapeyron equation.