Mitigating Risks of Ochratoxin A Contamination in Oats
Ochratoxin A (OTA) is a toxic metabolite produced by several species of fungal genera Penicillium and Aspergillus. The major OTA producer in temperate regions (i.e. U.S., Canada, Europe) is Penicillium verrucosum. Oat (Avena sativa), like any other cereal grain, can be contaminated with OTA when storage conditions are favorable for fungal growth. The presence of OTA exceeding the European Union maximum limit of 3 ppb in processed food has been reported in some samples of oat-based breakfast cereals from the US. The use of oat genotypes with limited OTA accumulation would be an effective way to reduce risks of OTA contamination in oat based products. The objectives of this study were to: 1) determine the frequently of P. verrucosum in oat grain produced in South Dakota, and 2) develop a methodology to screen oat genotypes for OTA accumulation. Grain samples from twelve oat cultivars grown at five locations in South Dakota from 2014 to 2016 were analyzed for the presence of P. verrucosum by direct plating on Dichloran Yeast Extract Glycerol Agar (DYSG) medium. Twenty-three out of the 360 samples (6.3%) evaluated had a very low percentage (0-16%) of kernels with P. verrucosum contamination. Three experiments with oat grain inoculated with P. verrucosum were carried out to study the effect of water activity, temperature, isolates of P. verrucosum, genotypes and time after incubation on OTA production. All these factors except genotype were found to have significant effects on OTA production by P. verrucosum in oats. A water activity of 0.90, temperature of 22.5°C, and P. verrucosum isolate C1136-1 were found to be highly favorable for OTA production in grain and could be used to assess varietal differences in grain OTA accumulation.