Author: Ndukwe Kelechi Samson
Department: Agricultural and Bioresources Engineering
Affiliation: Nnamdi Azikiwe University Awka
This study was carried out to determine selected physical and mechanical properties of Moringa oleifera seed for post harvest equipment design. Four levels of moisture content ranging from 10.250 – 32.343% dry basis for the seed and 9.048 – 34.374% dry basis for the kernel were used in the study. The properties studied were: major (length), intermediate (width) and minor (thickness) dimensions, arithmetic, geometric and equivalent sphere diameters, surface area, sphericity, unit volume, unit mass, aspect ratio, true and bulk densities, porosity, dynamic angle of repose, angle of internal friction, angle of friction, coefficient of static friction, 1000 grain mass, initial moisture content, bio yield force, rupture force, energy at rupture, deformation at rupture, crushing strain, modulus of elasticity and compressive (crushing) strength at two quasistatic orientations. The effect of moisture content on the properties of Moringa oleifera seed and kernel was investigated and the mean values of the physical properties of the seeds and kernels were observed to increase as moisture increases except in the porosity of the seed and kernel. The coefficient of static friction of seed and kernel were higher on plywood surface and lowest on glass and it was higher on all surfaces for kernels than for seeds. It was noticed that angle of repose of seeds was higher than for kernels. The bio yield and rupture force of Moringa seed and kernel decreased with increase in moisture content to minimum values and increased with further increase in moisture content. Second order polynomial equations with coefficients of term gave the best fit for the relationship existing among the mechanical properties concerned and seed moisture content at different loading axes from which the optimal moisture content for cracking the seed and crushing the kernel gave 25.375% d.b (at 2.753N/mm2) and 32.778% d.b (at 1.701N/mm2) at the horizontal and vertical positions respectively. The influence of moisture on cracking force was very important as little moisture differences created highly significant differences in the cracking forces. Moringa oleifera seed and kernel cracked easily at moisture contents of about 25.375% d.b (at 2.753N/mm2) and 32.778% d.b (at 1.701N/mm2) respectively. The optimal modulus of elasticity of the seed was lower on the horizontal orientation (78.745N/mm2 at 26.961% d.b) than that at the vertical loading (140.513N/mm2 at 29.360% d.b). All the properties have polynomial relationships with moisture gain which is depicted by high coefficient of determination, R2.
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