Study on postharvest physico-mechanical and aerodynamic properties of mungbean [Vigna radiate (L.) Wilczek] seeds

Determination of physical and mechanical properties can facilitate the design calculations of harvesting, handling, sorting and processing equipments. In this study, these properties of mungbean have been evaluated as a function of seed moisture content varying from 8.72 to 27.41% (d.b.). In this moisture range, the length, width, thickness, geometric mean diameter and surface area increased significantly (p < 0.05) from 4.32 to 5.10 mm, 3.33 to 3.54 mm, 3.30 to 3.59 mm, 3.62 to 4.01 mm and 41.1 to 50.6 mm2, respectively, whereas sphericity, porosity, bulk and true density decreased significantly (p < 0.05) from 83.80 to 78.63%, 39 to 36.56%, 841.3 to 730.7 kg/m3 and 1379.1 to 1151.8 kg/m3, respectively. Moreover, thousand seed mass, angle of repose and terminal velocity increased (p < 0.01) from 37.3 to 43.8 g, 31.6 to 40.3° and 4.9 to 5.8 m/s, respectively, by increasing the moisture content. The static coefficient of friction of mungbean seed increased against the surfaces of four structural materials, namely plywood (31.54 %), glass (29.54%), stainless steel (21.56%) and galvanized iron sheet (11.41%) as the moisture content increased from 8.72% to 27.41% d.b. Also, the results showed that the force required for initiating seed rupture decreased from 40.56 to 23.04 N and 59.82 to 19.51 N, and the energy absorbed at seed rupture increased from 7.20 to 27.36 mJ and 9.87 to 31.22 mJ by increasing in moisture content from 8.72% to 27.41% d.b. for vertical and horizontal orientations, respectively (p < 0.01).