Mycotoxins in hot spots in grains. I. Aflatoxin and zearalenone occurrence in stored corn

A hot spot that developed Aspergillus flavus growth in a bin of corn in central Illinois during warm weather was investigated for mycotoxins. High levels of aflatoxin (1000-1700 ppb (parts/billion)) were detected in samples collected near the centre of the hot spot that was defined by visible Asp. flavus sporulation. The location of the hot spot relative to an open window indicated the moisture necessary for mould growth, and aflatoxin formation could have come from rains blown through the window. Corn collected at all depths from 7 locations and probe samples taken under the hot spot were assayed for aflatoxin and zearalenone. Aflatoxin was not detected in samples collected furthest from the window. Zearalenone was detected in some of the samples collected, but it was not confined to any one part of the bin. The corn had been in the field an unusually long time before harvest because of cold, wet weather. Individual kernels selected from locations likely to contain aflatoxin and zearalenone were assayed for mycotoxins. Even in kernels connected with Asp. flavus mycelia, aflatoxin-free kernels occurred adjacent to highly contaminated kernels. Of 140 kernels analysed for both aflatoxin and zearalenone, 16 contained aflatoxin (260-38 000 ppb B1 + B2) and 12 had zearalenone (9000-1 700 000 ppb). In no kernel were both aflatoxin and zearalenone detected.