ABSTRACT
This study focused in determining the sorption isotherms of sweet sorghum seeds at varied conditions of temperature and water activity, ascertaining the isosteric heat of desorption. Seeds were dried in a forced-air oven at 40 °C up to reach moisture levels of 24, 19, 15, 12 and 8% (d.b.). Desorption isotherms of sorghum seeds were estimated by the indirect static method, and water activity (aw) was determined using a Hygropalm aw model 1 device. Temperature control was set at 10, 20, 30, and 40 °C in the B.O.D chambers. Experimental data were fitted using mathematical models regularly used to represent hygroscopicity of plant products. Results showed Chung-Pfost model as the one that best represents sorghum seed hygroscopicity. The isosteric heat of sorption increases with decreasing moisture contents; and the values for sorghum seeds with moisture content between 7.9 to 28.0% (d.b.) range from 3136.54 up to 2493.33 kJ.kg-1.
modeling; isosteric heat; isotherms
