Some physical properties of Pearl millet (Pennisetum glaucum) seeds as a function of moisture content

Two varieties of Pearl millet seeds (Penisetum glaucum) (Ex-Borno and SOSAT C88) were obtained from the Lake Chad Research Institute, Maiduguri-Nigeria and reconditioned to moisture contents ranging from 10% 20% w.b. The reconditioned seeds were then evaluated for dimensions, sphericity, bulk density, solid density, porosity, thousand seed mass, angle of repose and static coefficient of friction on five structural surfaces. Within the range of moistures analyzed, physical properties of millet seeds are related to the moisture content by polynomial equations. SOSAT C88 and Ex-Borno increased their width by 15.7% and 15.6%; similarly, their length increased by 15.3% and 19.8%, and their thickness increased by 22.4% and 7.8% respectively. Seeds from Ex-Borno were the smallest. Sphericity changed with the increase in moisture content with SOSAT C88 coming closer to a spherical form. The solid and bulk densities of the seeds for different moisture levels decreased with the increase in moisture content. The porosity started at 17% and 15.2 % and increased to 26.6% and 32.6% for SOSAT C88 and Ex-Borno varieties respectively. The thousand seed mass and angle of repose also increased with increasing moisture levels for both varieties. Both varieties showed a comparable behaviour in relation with the static coefficient of friction, this variable increased with moisture content on two structural surfaces namely concrete and plastic, but decreased with increasing moisture levels on glass, steel and aluminium. Regression equations that could be used to adequately express the relationship existing between the above properties and seed moisture were established.