Physical properties of sorrel (Hibiscus sabdariffa) seeds Original Research Article

Several physical properties of sorrel seeds were determined at 7.7% moisture content. The average of each of the three principal diameters and 1000-grain weight were 5.6 mm, 5.2 mm, 2.8 mm and 35.6 g, respectively. Mean values for sphericity and roundness were 68.6% and 70.2%. The coefficient of static friction was 0.64 parallel to the plywood grain, 0.81 perpendicular to the plywood grain, 0.52 on galvanized steel and 0.70 on mild steel. Dynamic angle of repose on the three structural materials ranged from 29.1° to 30.2°. The suspension air velocity for the whole seed, the kernel and the hull were 7.4, 5.8 and 3.9 m/s, respectively. These properties are often required for designing of cleaning and separating machines, fluidized transport systems, gravity and forced flow equipment, and other grain processing machinery.