Determining Physical and Mechanical Properties of Sorghum [Sorghum bicolour (L. Moench)] Grains of Selected Early Maturing Varieties Produced in Hararghe Zones, Ethiopia

Background: The high postharvest losses of sorghum reported in Hararghe Zones demand intervention through using technologies. Selection of design, improvement, and utilization of postharvest equipment depend on grain physical and mechanical property information of the concerned specific crop type and variety. However, this information is lacking for sorghum varieties produced in Hararghe Zones of Ethiopia. Objective: The aim the study was to generate data on physical and mechanical properties of grains of selected sorghum varieties. Materials and Methods: Three early (Makko, Malkam, and Qaqqaba) and one late maturing (Muyra) sorghum varieties were selected. Factorial combination of 4 × 6 treatments levels was adapted with different replications as recommended for every specific parameter. The grain size, shape, weight, volume, baulk density, true densities, porosity, angle of repose, coefficient of friction, and hardness were among variables studied. Descriptive statistics and ANOVA models were used for data analysis. Results: Means of the studied properties were found significantly different (P < 0.01) among the varieties and for variation of the moisture levels. The grains size, weight, porosity, coefficient of friction, and angle of repose were increased, while densities, hardness, and work of deformation were decreased with increase in moisture. The bulk and true densities were decreased from 0.910±0.05 and 1.38±0.08 g cm‒3 to 0.673±0.06 and 1.08±0.06 g cm‒3, respectively with a moisture increase from 10% to 20%. Conclusion: The study indicated large variations for the treatments used. The entire means of grain major diameters and coefficient of friction increased from 4.24±0.25 to 5.65±0.31 mm and from 0.412 to 0.598, respectively, while breakage forces decreased from 182.5±22.19 to 79.68±10.48 N for a moisture increase from 10% to 20%. Differences in the means of grain properties imply variability in design and adjustment specifications of postharvest implements needed for management of different sorghum varieties at different moisture levels.