Effect of Moisture Content on Physical Properties of Black Gram (Vigna mungo L.) for Designing Post Harvest Machineries

The physical properties of black gram are important indesign and fabrication of structures and machineries for harvesting, handling, transporting, processing and storage, and also for quality assessment. The physical properties of black gram were studied as a function of moisture content varying from 10.31 to 25.44% d.b. In the studied moisture range, the seed length, width, thickness, and geometric mean diameter varied from 5.16 to 5.31 mm, 4.42 to 4.85 mm, 4.25 to 4.45 mm, and 4.59 to 4.85 mm respectively. The sphericity, seed surface area, and seed volume varied from 0.891 to 0.914, 66.22 to 74.02 mm², and 46.37 to 60.23 mm³ respectively. The bulk density and true density decreased from 815.96 to 749.37 kgm⁻³ and 1425.74 to 1383.11 kgm⁻³ respectively, while the porosity increased from 42.75 to 45.80% with an increase in moisture content from 10.31 to 25.44% d.b. The terminal velocity increased from 8.58 to 10.54 ms⁻¹ and emptying angles of repose also increased from 24.80° to 29.24° with an increase in moisture content in the selected range. The coefficient of static friction of the black gram increased from 0.27 to 0.32, 0.25 to 0.30 and 0.26 to 0.28 against plywood, galvanized iron and stainless steel surfaces respectively with an increase in moisture content from 10.31 to 25.44% d.b.