Physical Properties of Roselle (Hibiscus sabdariffa L ) Seed

Abstract

The physical properties of Roselle seeds were determined at different moisture contents. The seeds were ground and classified into two particle sizes. The fine and coarse samples were conditioned by adding calculated amount of distilled water to different moisture contents from the initial moisture contents of 4.4 % and 5.14 %, respectively. The moisture contents were 4.4, 6.4, 8.4, 10.4 % for fine and 5.14, 7.14, 9.14, 11.14 % wb for coarse samples. The properties were determined using ASAE standards. The mean values of the physical properties of the seeds were determined as 4.75-4.85 mm length, 4.15-4.26 mm width, 2.62- 2.67 mm thickness, 3.73-3.83 mm geometric mean diameter, 648.31-619.14 kg/m³ bulk density, 20.13°-24.85° angle of repose, 17-18.5 mm² surface area, 52.6-58.3 % porosity, 1367.0-1487.4 kg/m³ true density, 29.7-40×10^-6 m³ volume, 5.8-7.1 m/s terminal velocity, 1.36-1.44 specific gravity. The coefficient of static friction was measured on mild steel (0.23-0.32), plywood with the grains parallel to the direction of motion (0.38-0.45) and glass (0.22-0.30). The physical properties of the seeds were found to increase as the moisture content increases with the exception of bulk density that decreased.