Moisture-Dependent Engineering Properties of Forastero Cocoa Bean Seeds

The effects of moisture content on the physical, mechanical and frictional properties of cocoa seeds (Forastero) were investigated at four different moisture content levels (9%, 14%, 19% and 26% dry basis). These properties are important in the design of appropriate machines 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 static and dynamic friction of the cocoa seed were determined by using standard methods. Data obtained were subjected to analysis of variance (ANOVA), linear regression analysis and descriptive statistics using Statistical Analysis System. The seed principal axes (length, width and thickness) were found to increase linearly from 20.84 mm to 24.05 mm, 11.42 mm to 14.80 mm and 8.60 mm to 10.39 mm. The arithmetic mean diameter, geometric mean diameter, sphericity and surface area was also found to increase linearly from, 13.62 mm to 16.40 mm and 12.69 to 15.46 mm, 0.61 to 0.67 and 505.91 mm2 to 750.88 mm2 accordingly. Porosity, bulk density and true density decreased as moisture content increases within the studied range. The static coefficient of friction was determined for four structural surfaces namely, fibreglass, galvanised iron sheet, rubber and plywood sheet. The plywood as structural surface had highest coefficient of static dynamic friction for all the structural surfaces investigated. The effect of moisture content on some the engineering properties of cocoa seeds studied showed significantly different (P < 0.05).