Image analysis as a non-destructive approach in selective characterization of promising Indian chickpea cultivars

Physical properties of food grains play an important role in optimizing the design parameters for machines and equipment, process automation, and determining the efficiency of the machine during various stages like harvesting, drying, storage, de-hulling, and other unit operations. Thus, the aim of the present study was to characterize the promising chickpea varieties for their physical properties comprising dimensional, gravimetric, and frictional parameters. The image processing technique was employed to study the geometrical variations among different chickpea varieties. The digital image processing approach offers rapid computation of shape and size parameters and validation of data obtained from manual methods by using digital vernier calipers. The dimensional parameters, namely length, breadth, and thickness were examined that were further used to calculate the derived parameters as mean diameters, sphericity, surface area, volume, and aspect ratio. The length of chickpea grains of different varieties lies in the range of 7.42±0.63 to 8.78±0.46mm, width varied from 5.33±0.38 to 6.50±0.42mm and thickness ranged from 5.17±0.46 to 6.23±0.45mm. The sphericity of the grains was found to vary from 75.84±3.03% to 82.89±3.92%. The 3-D imaging approach was adopted for the determination of various physical properties of grains, the results obtained are precise and thus this approach may help in the characterization of grains and in process automation. It was observed that the hilum portion of the chickpea contributes less than 5% to the total chickpea volume. Thus, if this portion is removed, it results in a significant improvement in the sphericity of the grains to behave as spheres. Therefore, calculations for physical properties may be carried out considering chickpea grains as spherical objects. During milling, the hilum portion is the first to be broken due to abrasion as it is brittle in nature, and this also results in a decrease in the coefficient of friction. Thousand kernel weight, bulk density, and true density were also examined as they are the important parameters that help in designing the storage bins. Chickpea cultivars were evaluated for the frictional properties, i.e., angle of repose and coefficient of static friction. The coefficient of static friction was determined over different common contact material surfaces and it was found that all the varieties have a maximum coefficient of friction over plyboard followed by the galvanized iron sheet and minimum on the glass surface.