Water Vapour Sorption Isotherms of Sheanut Kernels (Vitellaria paradoxa Gaertn.)

摘要

The water vapour adsorption and desorption isotherms in sheanuts kernels were determined at 25, 35 45 and 55°C. The static micro-gravimetric method using a Sartorius 4201 electromagnetic suspension microbalance was employed in the study. The sorption process was modelled by the BET, Oswin, Smith and the GAB equations while the Clausius-Clapeyron equation was used to calculate the net isosteric heats of sorption. The results showed a hysteresis effect between adsorption and desorption curves. The moisture content of the monolayer significantly depended on temperature and varied from 4.16 to 1.47% in adsorption and from 4.41 to 2.29% for desorption (GAB?s equation). The BET equation gave a lower range of 2.37 to 1.25% for adsorption and 3.41 to 1.59% for desorption. The sorption isotherms were best described by the GAB and Oswin models. The net isosteric heats of desorption (28.38 kJ moL-1) were greater than those of adsorption (21.98 kJ moL-1).