Temporary storage of high-moisture paddy using different aeration systems

Study was carried out to evaluate the effectiveness of aeration methods on maintaining the quality of freshly harvested paddy during short term storage. Two different aeration methods were evaluated under two type of air (natural and refrigerated air), two levels of grain initial moisture content (21-22 and 25-26 %), and three air flow rates, 0.02, 0.04 and 0.06 cubic m/hr kg. The effect of short term exposure to adverse condition such as when aeration is delayed was also investigated. Seven lots of high moisture rough paddy were stored for 10 days each experiment. Three lots aerated with natural air, the other three lots were aerated with refrigerated air. One treatment was left without aeration as control treatment. The effect of aeration methods on grain quality was evaluated in terms of grain final moisture content, milling quality, fungal growth, grain discoloration and whiteness degree. In refrigerated aeration, the cold and dry air reduced the grain moisture content to a range of 14 to 17 % (w.b) in comparison with 17 to 20 % in natural aeration. The range of air temperature and relative humidity was 17.5-22.7 deg C and 42-51 % in refrigerated aeration in comparison with 32-35 deg C and 73-80 % in natural aeration. Lower air temperature and relative humidity in refrigerated aeration reduced the grain moisture content and temperature to a level prevented spoilage of high moisture rough rice in comparison with ambient air. Mold growth associated with grain discoloration has increased as long as the grain temperature and/or moisture content remained high. Paddy with 21 percent initial moisture content had a relatively little quality changes in comparison with the 25 percent. Higher air flow rate would reduce the drying time and possibly mold activity and other quality changes during storage. Delays in starting aeration has increased mold growth and amount of deterioration especially in the treatments delayed for two days.