Moisture-dependent engineering properties of arugula seed relevant in mechanical processing and bulk handling

Knowledge of the engineering properties of seeds, grains, nuts, kernels, and fruits is vital in the design of planting, harvesting, and postharvesting machines. This study investigates moisture-dependent geometrical, gravimetrical, frictional, rheological, and aerodynamical properties of arugula seed. The length, width, and thickness of the seed distributions were modeled by the Normal, Log-normal, and Weibull probability density functions. In the moisture ranges of 4.68-20.50%, the major, intermediate, and minor seed dimensions increased from 2.01 to 2.35 mm, 1.60 to 1.98 mm, and 1.17 to 1.33 mm, respectively. The results indicated that Log-normal distribution had the best performance in most cases. Values of 1,000-seed mass, bulk density, particle density, and porosity ranged between 1.33 to 1.77 g, 703.07 to 644.37 kg m(-3), 1,160 to 1,392 kg m(-3), and 39.39 to 53.71% as in the above moisture ranges. The filling and emptying angles of repose increased from 29.21 degrees to 34.78 degrees and 37.95 degrees to 39.75 degrees, respectively, as the moisture content increased. Incremental trends were observed for terminal velocity in water and air and residual stress during relaxation tests. Decreasing trends were observed for drag coefficient, modulus of elasticity, maximum contact stress, toughness, hardness, rupture force, and reduced stress during relaxation tests. Practical Applications Arugula (Eruca vesicaria L. or Eruca sativa Mill L.) is a popular worldwide vegetable. Besides consuming its leaves as a vegetable, the oil extracted from its seeds has industrial uses. This study investigated properties of arugula seeds with varying moisture contents with a view to understand their relevance in mechanical processing and bulk handling. The results presented in the current work would contribute to designing the metering devices (distributors), sorters, separators, cleaners, transportation systems, conveyors, oil extractors, etc.