Effect of Moisture Content on Some Physical and Mechanical Properties of Three Varieties of Cowpea (Vigna Unguiculata (L)Walp)
The effects of moisture content on the physical, mechanical and frictional properties of three varieties of cowpea, Ife Brown, IT86D-1010 and IAR-339-1 were investigated at four different moisture content levels (i.e 15%, 20%, 25% and 30% dry basis). These properties are important in the design of appropriate machine for harvesting, processing, transporting, separating, packaging and storage processes. The axial dimension, mean diameter, sphericity, surface area, porosity, true and bulk density, angle of repose, coefficient of friction of the three varieties of cowpea were determined using standard method. The result obtained from the study revealed that length, width, thickness, arithmetic and geometric diameter, sphericity, surface area and 1000unit mass ranged from 9.87-15.21mm, 7.00-10.88mm, 5.49-8.47mm, 7.45-11.52mm, 7.24-11.19mm, 0.67-0.79, 164.70-393.43mm², 253.80-671.4g respectively. The mean porosity, true and bulk densities, hardness and angle of repose were investigated for the three varieties. The obtained results were 31.4-38.6, 1010.83 to 979.59 kg /m3, 1054.88 to 1014.54 kg/m3 and 1083.12 to 1037.53 kg/m3, 703.49 to 636.41 kg/m3, 689.29 to 622.12 kg/m3 and 726.91 to 672.05 kg/m3 and 24.3-29.7˚. The static coefficient of friction was determined for two structural surfaces namely, glass and plywood. The plywood as structural surface had higher coefficient of static friction for all the three varieties of cowpea investigated. Data obtained were subjected to analysis of variance (ANOVA), Duncan Multiple Range (DMR), Linear regression analysis and descriptive statistics using Statistical Analysis System. The result obtained revealed that there is significant different in both varietal and moisture content effect of these cowpea varieties on their physical, mechanical and frictional characteristics.