Canola Storage and Management

Heat damage in canola during storage degrades the oil quality, darkens the oil color, and increases the free fatty acid (FFA) content. You may have dried and cooled your canola for safe winter storage; however, heating and spoilage risk in stored canola is always present. If the stored canola is tough, exposed to extreme initial storage conditions such as high moisture and/or temperature for a significant period before drying and cooling, or if it contains high percentage of immature kernels, greens, and foreign material, the spoilage risk is even greater. During the winter months we often pay less attention to our stored commodities, thinking that our grain is safer during winter months. However, Canola temperature may rise significantly due to heat generated by the respiration of the seeds. Respiration also produces moisture, which accumulates on the surface of the grain, and often results in mold growth. Mold growth further accelerates the heating and moisture accumulation leading to sprouting, crusting, germination loss, significant grain spoilage, and mycotoxin development.

Heat damage in canola during storage degrades the oil quality, darkens the oil color, and increases the free fatty acid (FFA) content. You may have dried and cooled your canola for safe winter storage; however, heating and spoilage risk in stored canola is always present. If the stored canola is tough, exposed to extreme initial storage conditions such as high moisture and/or temperature for a significant period before drying and cooling, or if it contains high percentage of immature kernels, greens, and foreign material, the spoilage risk is even greater. During the winter months we often pay less attention to our stored commodities, thinking that our grain is safer during winter months. However, Canola temperature may rise significantly due to heat generated by the respiration of the seeds. Respiration also produces moisture, which accumulates on the surface of the grain, and often results in mold growth. Mold growth further accelerates the heating and moisture accumulation leading to sprouting, crusting, germination loss, significant grain spoilage, and mycotoxin development.

 

Greens in Canola

Green seeds in canola are result of harvesting a crop before it reaches the physiological maturity; however, frost is the major cause of canola green seeds in western Canada. Swathing the crop prematurely and non-uniform seed germination, plant growth, and seed development due to drought, heat and water stress, topography, and/or soil nutrient deficiency also result in higher greens. Green seeds in canola are highly undesirable in oil processing as the green chlorophyll color downgrades the quality of oil. In order to produce light color canola oil, additional processing is required to remove the chlorophyll color which increases the processing cost. A canola crop with higher green percentage is downgraded to lower grades and canola is highly discounted by elevators resulting in significant monetary loss to the producers. It is recommended to segregate and store canola with high greens in separate bins and closely monitor. Even a couple of loads with high green percentage may be enough to initiate the hotspot development. Sweating and self-heating in canola is common, even if harvested dry (<10% moisture).

 

Headspace Condensation

Often in winter and spring months, fluctuating weather conditions of warm days followed by cooler nights cause condensation inside the bin headspace and the grain near the top surface absorbs the condensed moisture. Due to this excessive grain moisture, mold may develop in the top layers of the grain as the headspace starts to warm with rise in ambient temperature. Grain crusting, sprouting, and mold are often visible on the top surface of the grain, which is mostly a result of headspace condensation.

 

Handling Tough and Frozen Canola

Tough canola stored during winter months should be dried to safe moisture levels as quickly as possible in spring when ambient starts to warm up to 50C and above. Tough canola in non-aerated bins is not recommended for summer holding. If drying is delayed or extended until summer, canola will warm up and with negligible cooling potential in warm air, canola will quickly heat up leading to significant spoilage. Often canola is cooled to temperatures much below freezing, e.g., -200C for winter holding though it does not offer any additional storage benefit. If you are planning to hold this canola during the summer months, it should be gradually warmed to 10-120C in spring to avoid condensation near inner bin walls during this time. Warm air near hot inner bin walls moves inwards and makes contact with the frozen or cool grain, and causing condensation as warm air cools below dew point temperature and reaches saturation. Canola should be carefully and gradually warmed in early spring without over heating in late spring and early summer operating the aeration fan.

 

Best Management Practices

For long term safe storage, canola should be cleaned, dried to 8-10% moisture content, and cooled to 2-3°C and monitored regularly. Un-cleaned canola with high dockage and immature and green seed percentage has a shorter safe storage life. These contaminants and damaged seeds not only absorb higher moisture than the healthy canola but also restrict airflow, making drying and aeration less effective through already narrow airflow paths around the small, spherical canola seeds. Storing and aerating canola in tall bins is less effective due to high static pressure required to overcome the resistance to airflow of the entire column of canola.

Stored canola must be regularly monitored using moisture and temperature cables. Increases in grain temperature and/or moisture are key spoilage indicators requiring immediate attention. Grain must be cooled as quickly as possible but avoid running the fan below freezing. In silos without aeration fans, grain must be turned during cooler periods for effective cooling. If you cannot control grain temperature by these means, grain must be immediately unloaded to prevent spoilage from further expanding heat damage and caking.

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