Physical Properties of Pearl Millet Grains as Function of Moisture Content and Variety

Abstract

Pearl millet (Pennisetum glaucum) is drought and heat tolerant grain with versatile application as food, feed or fuel. Designing the structures, machineries and equipment necessitated determination of grain properties. Different cultivars (Pusa composite 383, Pusa composite 701, Pusa composite 1201 and Pro agro 9444) of pearl millet were subjected to varying grain moisture content (10-5-30% db). Physical properties were examined at different levels of moisture content. Their mean dimensions viz. length, width, thickness and geometric mean diameter were 2.959-3.261, 2.359-2.701, 1.983-2.276, 2.416-2.667 (mm) respectively. Grain shape was determined in terms of 76.399-88.499 % aspect ratio and 0.791- 0.868 sphericity. The space and mass requirement was expressed as projected area, grain volume, thousand grain mass, bulk density, true density and porosity. Their respective values were 5.602-6.671 mm2, 5.896-8.417 mm3, 8.335-11.615 g, 699-846 kg/m3, 1170.4-1333.5 kg/m3 and 36.195-43.248 %. The static friction coefficient was 0.2063-0.4126, 0.2154-0.4237, 0.2273-0.4289 and 0.2384-0.4416 against wood, mild steel, galvanised iron and aluminium respectively. Angle of repose was 28.622-34.064 for emptying, while 23.492-29.978 for filling. Moreover, 19.814-53.194 N was needed for rupturing the grain. Properties viz. dimensions, geometric mean diameter, sphericity, projected area, volume and static friction coefficient and repose angle increased with increasing grain moisture content. Whereas, inverse relation was found for bulk density, true density and rupture force. Varietal difference was also significant (p≤0.05) for few properties under investigation. Moreover, regression with moisture content yielded linear equations having R2 values except sphericity and aspect ratio.