Water sorption isotherms of pistachio nut paste

Moisture sorption isotherms of pistachio nut paste were determined at 4 and 20 degrees C by using gravimetric method with saturated salt solutions. The moisture content of pistachio nut paste increased sharply at higher water activities as the temperature increased. Mathematical models of Brunauer et al., Anderson, Oswin, Halsey, Henderson, Kuhn, Filonenko & Chuprin and Peleg were evaluated to determine the best fit for the experimental data. In this study, Peleg model was found to be adequate model for pistachio nut paste. By using Clausius-Clapeyron equation, the heat of sorption was determined. As moisture content increased the heat of sorption decreased.