Simple fluorescence method for rapid estimation of aflatoxin levels in a solid culture medium.

Aflatoxin concentrations in agar media were estimated with a direct technique that quantifies the fluorescence of agar containing aflatoxins. Tubes containing 5 ml of an agar medium inoculated with spores of aflatoxin-producing Aspergillus isolates were incubated for 3 days at 30 degrees C and set in a carriage specifically designed to carry culture tubes in a scanning densitometer. Fluorescence (450 nm and above) was elicited in the agar by UV light (365 nm) and photometrically measured. Agar fluorescence directly correlated (r2 = 0.89 +/- 0.05, P less than 0.001) with the concentration of aflatoxin within the range 0 to 18.7 micrograms/g. The lowest aflatoxin concentration detected was 50 ng/g. The technique successfully differentiated the aflatoxigenic potentials of Aspergillus isolates.