Effect of Moisture Content on Some Physical and Mechanical Properties of Sira Bean Grains

Abstract

Some physical and mechanical properties of sira bean grains were determined as a function of moisture content in the range of 11.36% to 24.53% dry basis (d.b.) to provide information for the design of harvesting, handling, processing, and storage equipment and facilities. The average length, width, and thickness were 6.90 mm, 11.65 mm, and 5.39 mm, respectively, at 11.36% d.b. moisture content. The arithmetic and geometric mean diameters increased 7.01% and 7.67%, respectively, while the sphericity increased 3.07% in the moisture range from 11.36% to 24.53% d.b. Studies on rewetted sira bean grains showed that the thousand-grain mass increased 26.04%, the projected area 26.51%, the true density 10.54%, the porosity from 29.60% to 44.50%, and the terminal velocity 20.96%, while the bulk density decreased from 700.5 to 610.5 kg m-3 with an increase in the moisture content range of 11.36% to 24.53% d.b. The static coefficient of friction of sira bean grains increased linearly for six structural materials, namely, rubber (21.05%), aluminum (19.02%), stainless steel (18.03%), galvanized iron (27.59%), glass (22.38%), and MDF (medium-density fiberboard) (25.08%) as the moisture content increased from 11.36% to 24.53% d.b. The shelling resistance of sira beans decreased as the moisture content increased to 34.07%.