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April 02, 2019

Operation of modern aeration systems

by Daniel Wambeke, SCAFCO Grain Systems Company, USA

Grain quality is the highest just after harvesting. Providing proper conditions exist, grain can be stored for several years, with little or no detectable loss of quality. Under improper conditions, however, grain can begin to spoil within a few hours.
 


Grain spoilage is the result of microorganisms (bacteria, fungi and yeast) using grain nutrients for growth and reproductive processes. Microorganisms can produce heat during growth, that can increase the temperature of stored grain. The result can be “heat damage” that renders the grain unfit for human consumption or even animal feed.

Managing grain storage conditions
Successful grain storage requires that grain, and the atmosphere in which it is stored, be maintained under conditions that discourage or prevent the growth of microorganisms that cause spoilage. The major influences on the growth and reproduction of microorganisms in grain include: moisture, temperature, oxygen supply, pH, condition of the grain, storage time, initial infestation and the amount of foreign matter present.

Aerating stored grain, whether it is contained in bags, boxes, concrete or steel silos, or flat storage buildings, helps to maintain its quality. Before the principles of aeration were known or aeration equipment developed, the only method available to storage operators was to turn the grain in the storage system, thus providing some contact with fresh, cooling air.

This method required additional storage space, machinery and manpower for moving the grain, causing wear and tear on machinery and creating stress cracks and handling damage in the grain itself. This increased the percentage of fine material in the total grain mass.

Grain storage aeration systems have four basic functions. These systems:

• Remove storage odours, Aeration systems will remove undesirable odours from mouldy, sour or fermented grain.

• Protect against mould growth. High grain temperatures and moist grain conditions encourage the growth of mould and fungi. Lower grain temperatures, below 21°C, discourage this growth. Fungi growth rates decrease to a minimum from 2° to 5°C.

• Hinder insect activity. Insects multiply rapidly in grain, when the grain temperatures exceed 20°C. In general, insect reproduction is low when grain temperatures are below 15° to 16° C. Low temperatures impede insect movement, feeding and reproduction. However, lowering grain temperatures just 10° C (from maximum levels) can greatly reduce the movement and growth of some types of grain pests (others are affected differently), even if ambient atmospheric conditions do not allow the lowering of grain temperatures to the levels suggested above.

If it is possible to lower grain temperatures to 4° - 5° C, the resident insect population in the grain mass may starve and die. If climatic conditions at the storage site offer these kinds of temperature possibilities, it may be possible to avoid costly grain fumigation to deter insect infestations. Aeration is not, however, a total substitute for fumigation or good management practices.


Read more HERE.
 

The Global Miller
This blog is maintained by The Global Miller staff and is supported by the magazine Milling and Grain
which is published by Perendale Publishers Limited.


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