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Drying and Storing Canola
Harvesting canola at the proper stage is important. The color of the seed will not change during drying and storage and canola is severely discounted at market if more than 2% of the seed is green. Canola must be exposed to sunlight for the color change to occur.
Recommended moisture content of canola seed is 10% for short term (over winter) and 8% for longer term storage. Allowable storage times for canola can be pulled from a chart for cereal grains by subtracting 5 percentage points from cereal grain moisture content. For example, the allowable storage time of 18% moisture wheat at 60 degrees F. is about 50 days, so the allowable storage time for 13% moisture canola at 60 degrees F. is also about 50 days.
Storage management of canola, including aeration, is critical. Heating in storage lowers protein quality and increases the amount of free fatty acid, greatly reducing canola's value.
Canola reportedly goes through a "sweat" during the first month of storage, so aeration and frequent monitoring during this period are very important. Canola should be aerated shortly after storage, then cooled whenever average outdoor temperatures are 10-15 degrees cooler than the canola.
Temperatures need to be limited during high temperature drying. At moisture contents up to 12%, a drying temperature of 180 degrees F. can be used with dryers that mix the seed as it's dried. Over 12% moisture, the dryer temperature needs to be limited to 160 degrees F., even with mixing in the dryer. Without mixing the dryer temperature needs to be limited to 140 degrees F.
Natural air/low temperature drying with an airflow rate of .75 cubic feet per minute per bushel will dry canola at initial moisture contents up to 12%, and a rate of 1 cubic foot per minute per bushel permits drying canola at up to 13% moisture.
Higher airflow rates are not economical because of the large resistance to airflow of canola seed. Resistance to airflow through Argentine canola is about twice that of wheat. The static pressure required to move air through the Polish type canola is somewhat greater than through the Argentine type. Most of our canola is Argentine.
Canola is expected to dry to acceptable storage moisture contents using natural air drying during September and October. Supplemental heat may be added if canola does not reach the recommended storage moisture content with natural air drying. The equilibrium moisture content is similar to that of oil sunflower.
Do not warm the air more than 5 degrees F. or the canola will be over-dried. The estimated drying time using an airflow rate of 1 cubic foot per minute per bushel is about 30 days; at the .75 cubic foot rate drying time is about 40 days.
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