Moisture-dependent physical properties of Moringa oleifera seed relevant in bulk handling and mechanical processing

Physical properties of Moringa oleifera seed and kernel were determined as a function of moisture content. In the moisture ranges of 8.43–31.66% (d.b) (seed) and 6.75–31.5% (d.b) (kernel), the major, intermediate and minor axes of seed increased from 1.19 to 1.32 cm, 1.02 to 1.08 cm and 1.00 to 1.05 cm respectively, while those of kernel were in the range of 0.74–0.79 cm, 0.64–0.71 cm and 0.61–0.65 cm respectively. 1000 seed and kernel weights increased with moisture content and ranged between 0.5–0.6 kg and 0.2–0.38 kg in the above moisture ranges. Particle and bulk densities of seed and kernel increased from 0.88 to 0.98 kg m−3 and 0.51 to 0.83 kg m−3 respectively and from 0.55 to 0.64 kg m−3 and 0.64 to 0.7 kg m−3 respectively, as moisture content increased in the above ranges. Porosity of seed and kernel increased from 37.5 to 68%, and from 20 to 74% respectively as moisture content increased. Static and kinetic coefficients of friction varied with structural surface and increased from 0.272 to 0.725 and 0.235 to 0.689 respectively for seed, and from 0.211 to 0.732 and 0.215 to 0.566 respectively for kernel. Angle of repose of seed and kernel increased from 17.1° to 23° and 13.1° to 21.8° respectively in the above moisture content ranges. Regression models that adequately expressed the relationships existing between the physical properties of moringa seed and kernel with moisture content were presented.

► Physical properties of Moringa oleifera seed and kernel were a function of moisture content. ► Axial dimensions increased with increase in moisture content. ► Particle and bulk densities increased linearly with moisture content. ► Static and kinetic coefficients of friction varied with moisture content and structural surface. ► Angle of repose increased with increase in moisture content.