CORN DRYING
Alternatives ~ Better Quality, Lower Cost!
By Ralph Brown, University of Guelph

A long-term study at the University of Guelph to establish a consistent supply of high-quality Ontario corn for food and industrial markets looks like it will have a double impact on producers. Not only will the innovative drying and storage methods improve quality of corn...but drying costs may fall too!

One idea is for short-term (4-5 months) cold storage of damp grain as an alternative to heated-air drying for corn used in wet milling (i.e. Casco, which processes about 25 per cent of Ontario’s corn production), and potentially for food use, too. Experiences with low-temperature drying have shown us that late-harvested corn coming off the field at 20-22 per cent moisture need not be dried immediately. In fact, it can be stored safely for several months, provided it’s kept cold. The quality deterioration usually associated with high-temperature drying (e.g., stress-cracked kernels, starch-protein binding) is avoided, and fuel energy is saved by eliminating the dryer.

Work is proceeding on management issues around damp corn storage. We’re addressing questions such as:

• What temperature range in storage is “safe”?
• Is there a potential for mycotoxin development from mold growth in damp storage?
• Will storage extender chemicals such as potassium sorbate, sulphur dioxide (SO2) or organic acids play a significant role?
•Does wet milling quality deteriorate after several months of damp storage?

Damp corn storage will not fit into everyone’s production system, but some of the other drying innovations will have a broader impact. Anyone who dries corn for on-farm use or for the feed market is interested in better quality, especially if fuel costs are cut too. In a wet harvest year like 1997 there is always a conflict between drying capacity and corn quality...with quality usually suffering as the dryer temperature gets turned up to move more tonnes through the system. The effects of drying on corn quality - stress cracking, breakage susceptibility, low test weight and hidden damage (chemical or structural changes to internal components) - are exaggerated when the initial moisture content and the dryer air temperature are both high. Corn harvested at 32 per cent moisture must be treated differently than the same hybrid coming off at 25 per cent. Maximum kernel temperature, moisture removal rate (a function of air temperature, air humidity and the ratio of air flow to grain flow) and the cooling rate after drying are the main factors which influence final quality.

A “smart” dryer control system, which will act much like a skilled human operator continuously monitoring the dryer settings to maximize dried corn quality, is under development. The control system will take into account both initial and final grain moisture content, as well as the dryer operating parameters. The moisture removal rate will be regulated by varying the drying temperature as well as the amount of exhaust air recycle, which will also improve fuel efficiency.

Thermal insulation for in-bin dryers is another area of active research. There are really two reasons for considering bin insulation – to reduce the loss of heat energy, or to prevent condensation on the inside wall of low-heat, full-bin dryers. For roof dryers in tall bins it makes sense to insulate the outside of the bin, if the heat losses from the hot bin walls are more expensive than the cost of the insulation. We have been doing some on-farm measurements to determine the economics of insulation for energy conservation.

However, with a condensation problem, the solution is more straight forward. If there is a crust of moldy corn left on the bin wall after drying, the quality of the entire batch may suffer. In a late harvest year such as last year, condensation due to low outside temperatures is inevitable. Adding insulation to the inner or outer bin wall reduces the thermal gradient and consequently reduces condensation and spoilage. Any fuel savings are a bonus! The jury is still out on whether it is better to insulate the inside or the outside of the bin.

The Guelph team has been formed under the sponsorship of OCPA to respond to the research needs of the Ontario corn industry. We intend to work closely with producers, in most cases by doing collaborative on-farm research with innovative operators. We welcome all inquiries, input and opportunities to work with new co-operators.

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