Moisture dependent physical properties of nigella seeds

A study on the nigella seeds (Ajmer Nigella-1) was performed to investigate the effect of seeds moisture content on their physical properties as these are very important to design post harvest equipments. The physical properties of the nigella were evaluated as a function of moisture contents in the range of 5.2 to 25.1% dry basis (d.b.). Seed geometric parameters such as average length, width, thickness, geometric mean diameter, volume, increased with the increase in seed moisture, except seed sphericity and surface area, which remain unchanged as statistically non-significant. The 1000-seed mass increased linearly with increase in moisture. Bulk density and true density of nigella decreased when seed moisture content was raised from 5.2 to 25.1% d.b. The porosity of nigella increased up to 19.9% moisture content and then decreased slightly. The angle of repose and coefficients of static friction on four different surfaces (plywood, mild steel, galvanized iron and glass) and terminal velocity increased with seed moisture.        Key words: Nigella sativa, physical properties, frictional properties, seed spices.