Maintaining Quality in On-Farm Stored Grain

Industry concerns over grain quality, along with increased production of specialty, identity-preserved and food-grade crops, have placed increased focus on grain quality and storage issues. Most damage that occurs during storage is caused by molds and insects.

Grain spoilage occurs as microorganisms feed on the nutrients in the grain. As they grow and develop, these microorganisms produce heat, which increases the temperature of the surrounding grain. This heating may result in hot spots.
If the temperature and moisture in the grain are just right, the major mold species Apergillus, Fusarium and Pencillum may produce mycotoxins such as aflatoxin, fumonisin, DON and zearalenone. These mycotoxins can cause serious illness and even death when consumed by humans or livestock.

The presence of mold does not mean that mycotoxins will be present, but rather the potential exists for their development with the right combination of temperature, grain moisture content and storage time. Even more frustrating is the fact that the absence of mold does not guarantee that mycotoxins are not present. This is because the growth of the mold may not be extensive enough to cause visible damage, but nevertheless, it can still produce toxins.

Economic losses caused by stored grain insects can be measured in several ways. When the grain is sold, costly discounts are levied for insect damage. More importantly, infested grain results in dissatisfied customers and a poor reputation in marketing channels. Left untreated, insect infestations will eventually lead to other storage problems. Insects give off moisture that can cause grain moisture contents to increase enough to create a mold problem. Mold activity will in turn raise temperatures and result in an increased rate of insect reproduction. Greater numbers of insects create more moisture, and the cycle is repeated at an ever-increasing rate. Management of field insect pests often receives more attention than storage pests. However, storage losses are often equal to or greater than field losses due to dockage and contamination of the grain.

Grain quality will not improve during storage. At best, the initial quality can only be maintained. Once grain is stored, the quality depends on your control and management of the storage system. Molds and insects need adequate food, moisture and temperature to survive and reproduce. Since food is always available in stored grain, grain moisture and temperature must be maintained at levels that are detrimental to mold and insect growth.


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