An indirect solar dryer was tested for drying sheanut kernels. The influence of tray distance from heat source, airspeed and particle size on drying kinetics was investigated. Optimum drying air parameters obtained in the dryer were airspeeds of 1 and 1.4 m/s and a temperature of 40°C–45°C. Sheanut kernel slices dried entirely in the falling rate period. Drying rate decreased with increase in particle size. The effect of particle size on the drying rate suggested that, the drying process was controlled by internal mass transfer mechanisms. Drying kinetics was modelled with characteristic drying curve and diffusive models. Effective moisture diffusivities of sheanut kernel slices calculated without shrinkage were greater than those calculated with the incorporation of shrinkage by a value of about 50%. Acid and peroxide values indicated that butter from the dryer could be classified either as Category 1 or 2 irrespective of the drying conditions to which the kernels were subjected.
Keywords: indirect solar drying, modelling, shrinkage, sheanut kernels