Effects of moisture content on physical and mechanical properties of African locust bean (Parkia biglobosa) seed

Abstract

This study investigated the effects of moisture content on some physical properties of African Locust Bean (Parkia biglobosa) seed, a seed used for  traditional condiment in rural Nigeria. The physical properties which were investigated at three moisture content, 7.5, 15 and 22.2% wet basis include  axial dimension ( length, width and thickness), geometric mean diameter, shape (in terms of sphericity), size ( in terms of unit volume, unit seed mass and  surface area), bulk density, unit density, angle of repose, porosity, coefficient of static friction and hardness. The mean values of the physical  properties of the seeds determined were: 9.71-11mm length, 7.9- 8.46mm width, 4.57-4.75mm thickness, 7.02-7.61 mm geometric mean diameter, 72.4 –  69.3 sphericity, 0.156-0.272g unit seed mass, 27.87- 39.7 % porosity, 29.84 -28.86N hardness, 18.6°- 29.1° angle of repose, 0.185-.23cm³ unit volume,  84.88-103.94mm² surface area, 0.943-0.723 g/cm³ bulk density, 1.105-1.186g/cm³ unit density. The coefficient of static friction was measured as  (0.34-0.62) on galvanized steel, (0.6-0.81) on plywood and (0.25-0.55) on glass. The physical properties of the seeds were found to increase as the  moisture content increased with the exception of bulk density, sphericity and hardness that decreased and were all well correlated with moisture content.  These properties are useful in the design of equipment used in planting, processing, handling and storage of African locust bean seed.