Water sorption isotherms of date pastes as influenced by date cultivar and storage temperature

The water sorption isotherms of pastes of three date cultivars - Ruziz, Khudari, and Khlass - were determined using the static method of saturated salt solutions at three storage temperatures: 5 degrees C, 25 degrees C and 40 degrees C. The effect of temperature on sorption behavior was more pronounced than the effect of date cultivar. Equilibrium moisture content decreased with increasing temperature at water activities below 0.45-0.55. However, above 0.45-0.55, equilibrium moisture content increased with increase in temperature, mainly due to the additional dissolution of sugars at higher temperatures. The experimental data fitted well with GAB, Iglesias and Chirife, and Halsey equations, suitable for high sugar foods. (C) 1999 Elsevier Science Ltd. All rights reserved.