Seed Moisture Influence on Some Physical and Mechanical Properties of African Mesquite (Prosopis africana)

Abstract

The physical and some mechanical properties of Prosopis africana seeds (African mesquite) as affected by seed moisture content in the range 10–22% wet basis (w.b.) were investigated. Mohsenin, Stepanoff and ASABE standard methods were used in determining the properties. Results showed that there was increase in seed length (11.40–12.90 mm), width (8.10– 9.60 mm) and thickness (4.8–5.9 mm) while arithmetic and geometric mean diameters increased in the range; 8.1–9.4 mm and 7.5–8.9 mm respectively. Increases in bulk density (508 – 856 kgm-3), surface area (176 – 249 mm2) and sphericity (0.66–0.70) were recorded while a decrease was observed in true density (1205.9–1090 kgm-3) with increasing seed moisture content. Increase was also observed in static angle of repose (30.8 - 36.2o). Static coefficient of friction increased on plywood (26.7 - 32.2), glass (25.7 - 33.8), mild-steel (26.2 - 31.0), galvanized iron (27.5 - 32.7), rubber (27.5 - 31.5), aluminium (26.0 - 28.5) and stainless steel (24.0 - 31.8). Shear stress was highest at 22% moisture wet basis (w.b.) under 500 g load (6.3 gcm-2) and lowest at 10% moisture w.b., under 200g load (2.0 gcm-2). Effect of seed moisture content on all the properties was statistically significant (P=.05) except static coefficient of friction on aluminium and mild steel surfaces. All the properties are pre-requisite for the engineering design and development of equipment for the handling and processing of African mesquite; the purpose for which baseline data was developed in this work.