INVESTIGATION ON THE EFFECT OF MOISTURE CONTENT ON PHYSICAL AND THERMAL PROPERTIES OF OFADA RICE (ORYZA SATIVA L.) RELEVANT TO POST-HARVEST HANDLING

Abstract

Knowledge of the physical and thermal properties of agricultural products is essential in order to design equipment for processing, sorting, sizing and other post-harvest equipments. Some engineering properties of ofada rice were investigated as a function of moisture content in the moisture range of 9.14 to 25.36% wet basis (w.b.). The increase in moisture content was found to increase the length, width, thickness, arithmetic mean, geometric mean, surface area, volume, sphericity and aspect ratio of the rice grain respectively. Thousand grain mass, bulk density and angle of repose also increased from 19.53 to 25.83 g, 789.33 to 865.33 kg/m3, 35.41 to 42.90º as moisture content increases. Static coefficient of friction carried out on different surfaces include plywood, mild steel, galvanized iron, glass and stainless steel were also found to increase with an increase in moisture content, the values ranged from 0.4951 to 0.5703, 0.5024 to 0.5970, 0.5511 to 0.6371, 0.4350 to 0.5170 and 0.4417 to 0.5206, respectively. The specific heat capacity, thermal conductivity and thermal diffusivity ranged from 1.46 to 1.77 kJ/kgK, 0.137 to 0.198 W/mK and 0.9 to 0.12 × 10-7 m2/s, respectively. The thermal properties were observed to increase as moisture content increases. This study consequently asserts that physical and thermal properties of ofada rice are moisture content dependent and that the results could be exploited by rice processors in the post-harvest processing of rice