“Grain cooling is a comprehensive solution for postharvest management and conservation of a grain bulk. It brings benefits which keep quantity, quality and the processing of a grain in the most economic condition. Its implementation in the warm and humid climates will lead to essential improvement of grain handling, loss reduction and good management practice, which has been proven in moderate climate already for more than 50 years.”
Grain is the essential base of human nutrition and feeding in animal husbandry. It needs to be available throughout the processing and can’t be replaced. Therefore it is mandatory to store it during the harvest time when quality and price are at their best. Most mills have invested in bulk storage facilities like silos to simplify the handling for the processing and to maintain the quality of the grain during the storage. However the management of the storage faces new challenges mostly. They are caused by the nature of grain, the storage environment and the postharvest treatment. Main issues are the high and uneven moisture content, high ambient temperatures and relative humidity, heat rise during storage, weevil and mould infestation. All of those cause extra efforts, additional cost or reduction in processing efficiency which increase by longer storage time. Grain cooling eases the trouble and simplifies the management to one treatment solution for all constrains of grain storage.
THE WAY OF GRAIN COOLING
The grain cooler is connected to the grain storage by a flexible hose. The treated air is blown into the grain bulk. The air flow passes the grain and removes the heat of the grain. The air becomes humid and warm and exits the storage bin through vents at the top. The grain cooling continues until the entire bulk is cooled to the desired temperature, usually in a range of 10 to 18°C depending on the storage time. Afterwards the grain cooler is turned off and the air inlet and vent openings are closed. The cooled grain remains in the silo until it is removed or cooled again if the temperature will increase after several months of storage. Figures of the application at a vertical silo and warehouse are shown in Figure 1 and 2.
THE ACHIEVEMENTS OF GRAIN COOLING FOR GRAIN STORAGE
Prevention of Respiration Loss
Grain continues to respire after being harvested. Losses in freshly harvested grain are primarily caused by its cellular respiration and its heating. The rate of the activity is dependent on the grain’s moisture content and temperature as shown in Figure 3 (Jouin, 1964). Respiration becomes exponentially intensive as the temperature and moisture content of grain increase.