DESORPTION ISOTHERMS OF WATER IN TRIFOLIATE YAM )Dioscorea dumetorum Pax.(

Desorption isotherms of water in trifoliate yam (Dioscorea dumetorum Pax) were determined using a dynamic gravimetric method at temperatures of 20°, 34°, 46° and 62°C, in the relative humidity range from 11 to 86% A nonlinear least squares regression program was used to fit the measured data to the Modified Henderson, the Modified Halsey, the Chung-Pfost, and the GAB sorption models. The GAB model gave the best fit. The net isosteric heat of sorption, estimated using the Clasius-Clapeyron equation, ranged from 1412 kJ/kg at a moisture content of 0.05 kg/kg, dry basis, to 325 kJ/kg at 0.20 kg/kg. Results obtained in this study should be important in controlling the water content of yam during processing, handling, packaging and storage.