Physical Properties of Browntop Millet, Rajmudi Rice, and Polished Rice: A Comparative Characterization

Abstract

Brown top millet (BTM) is an underutilised ancient cereal with exceptional nutritional value and remarkable agronomic resilience. Knowledge of grain physical properties is essential for the design and optimisation of handling, grading, milling, storage, and processing equipment. This study evaluated and compared the physical properties of BTM, Rajmudi rice (RR), and polished rice (PR). Significant differences were observed among the grains in dimensional properties, shape, density, porosity, thousand-kernel weight, angle of repose, and colour values. BTM exhibited the smallest grain dimensions, with a geometric mean diameter of 1.37 ± 0.004 mm, an equivalent mean diameter of 1.40 ± 0.006 mm, and an arithmetic mean diameter of 1.43 ± 0.006 mm. Its sphericity and aspect ratio were 75.0 ± 0.88% and 0.854 ± 0.03, respectively, indicating a nearly spherical grain shape. The thousand-kernel weight of BTM was 2.30 ± 0.04 g, which was significantly lower than those of PR and RR. The bulk density (802 ± 5.74 kg/m3), true density (1438 ± 0.04 kg/m3), and porosity (41.0 ± 0.41%) of BTM were intermediate between those of RR and PR. The angle of repose of BTM was 31.1 ± 0.23°, which was lower than that of RR and comparable to that of PR. BTM exhibited L*, a*, and b* values of 57.1 ± 0.064, 8.80 ± 0.085, and 17.3 ± 0.022, respectively, indicating lightness comparable to RR but lower than PR, the greatest redness among the samples, and intermediate yellowness.