Geometric and mechanical properties of mung bean (Vigna radiata L.) grain:: Effect of moisture

In this research, selected geometric and mechanical properties of mung bean grain were evaluated as a function of moisture content. Five levels of moisture content ranging from 7.28 to 17.77% d.b. (dry basis) were used. The average length, width, thickness, arithmetic and geometric mean diameters, sphericity, thousand grain mass and angle of repose ranged from 5.145 to 6.199 mm, 3.760 to 4.474 mm, 3.537 to 4.223 mm, 4.147 to 4.965 mm, 4.090 to 4.893 mm, 0.795 to 0.789, 52.3 to 64.6 g, and 25.87 to 29.38 degrees as the moisture content increased from 7.28 to 17.77% d.b., respectively. The bulk density was found to be decreased from 821.3 to 745.2 kg/m(3), whereas the grain volume, true density, porosity, terminal velocity, and projected area were found to be increased from 27.88 to 47.33 mm3, 1230.0 to 1456.7 kg/m(3), 30.43 to 46.57%, 4.86 to 5.29 m/s, and 17.48 to 19.26 mm(2), respectively. There is a 43% increase in surface area from grain moisture content of 7.28 to 17.77% d.b. The static coefficient of friction on various surfaces increased linearly with the increase in moisture content. The rubber as a surface for sliding offered the maximum friction followed by galvanised iron, medium density fibreboard, stainless steel, aluminium and glass sheet. As moisture content increased from 7.28 to 17.77%, the rupture forces values ranged from 67.39 to 39.44 N; 63.86 to 42.18 N, and 53.96 to 41.79 N for thickness (Z axis), length (Y-axis) and width (X-axis), respectively.