Effect of moisture content on some physical and mechanical properties of faba bean (Vicia faba L.) grains

This study was carried out to determine the effect of moisture content on some physical properties and mechanical behaviour under compression load of faba bean grains. Four levels of moisture content ranging from 9.89% to 25.08% d.b. (dry basis) was used. The average length, width, thickness, geometric mean diameter, unit mass of grain, sphericity, thousand grain mass and angle of repose ranged from 18.40 to 19.77 mm, 12.54 to 13.66 mm, 7.00 to 8.03 mm, 11.68 to 13.01 mm, 1.147 to 1.301 g, 63.47% to 65.78%, 1140.15 to 1332.67 g and 13.94° to 18.58° as the moisture content increased from 9.89% to 25.08% d.b., respectively. As the moisture content increased from 9.89% to 25.08% d.b., the bulk density was found to decrease from 419.59 to 381.60 kg/m3, whereas the grain volume, true density, porosity and surface area were found to increase from 0.998 to 1.099 cm3, 1151.33 to 1206.21 kg/m3, 63.09 to 67.21% and 4.29 to 5.31 cm2, respectively. The static and dynamic coefficients of friction on various surfaces, namely, galvanized metal, chipboard, mild steel, plywood and rubber also increased linearly with an increase in moisture content. The mechanic properties of faba bean were determined in terms of average rupture force, specific deformation and rupture energy along X-, Y-, and Z-axes. Specific deformation and rupture energy of the faba bean grains generally increased in magnitude with an increase in moisture content, while rupture force decreased for compression along X-, Y-, and Z-axes. The highest rupture force, specific deformation and rupture energy in all moisture content levels were obtained for faba bean grains loaded along the Z-axis.