Effect of Air-Drying on Physical Properties of Shea Kernel

Abstract

In order to design postharvest processing equipment for shea kernel, it is necessary to evaluate its physical and engineering properties. In this study, the physical properties of shea kernel were investigated at five moisture levels for two size categories of large size kernel (LSK) and small size kernel (SSK) as the kernels were air-dried from an initial high moisture content. As the SSK dry from moisture content of 73.38 to 6.58% (db), major, intermediate and minor diameters decreased from 30.80 to 23.32mm, 21.63 to 15.76 mm and 19.42 to 13.36 mm, respectively. The geometric mean diameter also decreased from 19.96 to 19.54 mm while sphericity and surface area also decreased from 0.76 to 0.73 and 17.31 to 9.08cm2 , respectively. The mass and volume as well decreased from 6.82 to 3.14 g, 6.8 to 2.59 cm3 while kernel density increased from 1.04 to 1.26 g/cm2 as the moisture content decreased. The static coefficient of friction on galvanized iron, wood and steel decreased from 0.68 to 0.39, 0.76 to 0.45 and 0.57 to 0.42 respectively. The angle of repose however increased from 23.4 to 30.5 degrees. Corresponding values were also observed for LSK categories. Regression equations were utilized to model the relationship between moisture content and the physical attributes for the shea kernel.