Authors:   A.M. Olaniyan, A.O. Yusuf, O.F. Osadipe

Abstract

Shea kernel roasting prior to shea butter extraction is done to prepare the kernel in a good condition for the extraction of the fat (shea butter). Besides, roasting reduces the viscosity of oil to be extracted, ruptures the oil cells, adjusts the moisture content of the kernel to the optimum level for oil extraction and destroys or deactivates enzymes which inhibit the release of oil from the kernel. All these facilitate the extraction process. A small scale machine for roasting shea kernels prior to shea butter extraction was designed, constructed and tested The machine consists of a hopper, top cover, roasting chamber, chamber support, an auger or screw conveyor, temperature-controlled heating device, a discharge outlet, a 2 hp electric motor and a speed-reduction gear box. The machine derives its power from the electric motor through a gear reduction box to the shaft of the screw conveyor. Shea kernel is fed through the hopper into the roasting chamber and then conveyed to the discharge end after being roasted. Heat is supplied to the kernel inside the roasting chamber form two 750 W ring-type heaters placed at both ends of the chamber. The roasting temperature is regulated by a thermostat connected to the electric heaters. The machine has a capacity of 20 kg/h and the production cost was USD100. Test results revealed weight losses of 12.1, 27.6, 31.8 and 32.8 % in the kernels at roasting temperatures of 50, 70, 90 and 110 0C respectively. The kernels were of uniform deep-brown colour with clear film of oil on the surface after roasting indicating that they experienced uniform roasting.