2020 Volume 70 Issue 1 Pages 7-13
The dichlorvos-ammonia (DV-AM) method is a simple and sensitive visual method for detecting aflatoxigenic fungi. Since aflatoxin contamination has been frequently reported in ground nuts and tree nuts in many countries, we herein used the DV-AM method for the detection of aflatoxigenic fungi in imported raw nuts and seeds: peanuts from South Africa, macadamia nuts from Australia, pistachio nuts from Iran, macadamia nuts from Kenya, almond nuts from California, U.S., cashew nuts from Viet Nam, hazelnuts from Turkey, pumpkin seeds from China, sunflower seeds from Bulgaria, and walnuts from the U.S. Using the DV-AM method revealed that yellow fungal colonies surrounding the peanuts and the macadamia nuts were changed to red by ammonia treatment. Thin-layer chromatography analyses showed that the red fungi from the peanuts produced mainly aflatoxin B1 and the red fungi from the macadamia nuts produced mainly aflatoxins B1 and G1. Based on their calmodulin gene sequences, the peanuts' fungi were identified as Aspergillus flavus, and those from macadamia nuts from Australia were Aspergillus parasiticus. Aflatoxigenic fungi were not detected in the other nuts and seeds. These results demonstrate that the DV-AM method can be used to detect aflatoxigenic fungi in various imported foods. This method will also be useful for the determination of critial control points for food safety at different stages of the food chain: harvesting, sorting, washing, various food processes, and transporting.
