Development of a method for direct visual determination of aflatoxin production by colonies of the Aspergillus flavus group

This report describes a simple, rapid and reliable method for screening the aflatoxin production by moulds of the Aspergillus flavus group. Strains were cultivated on yeast extract agar to which methylated β-cyclodextrin derivative plus sodium desoxycholate was added. Production of aflatoxins was readily detectable by direct visualisation of a beige ring surrounding colonies after an incubation time of 3 days at 28 °C. When this ring was examined under UV light, it exhibited blue fluorescence. The presence of aflatoxins was confirmed by extracting the medium with chloroform and examining the extracts by HPLC with fluorescence detection.