Potential of development of mycotoxins in stored durum wheat under near-ambient drying conditions in Western Canada

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Parker, Vincent Russell
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The use of near ambient air drying for the preservation of wheat stored in granaries is common in Western Canada. Guidelines have been developed to assist farmers in selecting appropriate drying methods. During this process the top layer of wheat can remain at moisture contents (m.c.) greater than the safe storage limit, 14.5% wet bulb (wb), for up to 12 weeks. This study tested the effects of this drying procedure on the development of ochratoxin A (OTA) using 1 m3 bulks of durum wheat at 18% m.c. (wb) contained within steel bins inside a Weather Simulation Lab. In a second study using 20 L volumes of wheat at a m.c. of 20% (wb) within an environmental growth chamber potential development of OTA was also evaluated. The wheat was exposed to two treatments, airflow and no airflow, for a period of 12 weeks under conditions of high relative humidity (greater than 80%) and typical Manitoba fall temperatures. The storage quality parameters of germination, fat acidity value, and presence of OTA were measured weekly. It was found that high moisture wheat stored under all treatment conditions showed a rapid decrease in germination and increase in fat acidity value over time, with no significant difference between the treatments. Under the tested conditions the development of ochratoxin A was not detected in significant quantities in the 1 m3 bulks of grain but was detected in the smaller 20 L bulks.
Mycotoxins, grain storage, ochratoxin A, near-ambient air drying