Fluorescence Excitation–Emission Features of Aflatoxin and Related Secondary Metabolites and Their Application for Rapid Detection of Mycotoxins

Abstract

The persistent occurrence of aflatoxins in food and feed remains a problem for producers of commodities subject to colonization with toxigenic molds. Aflatoxins are secondary metabolites of fungi of the Aspergillus spp. associated with deleterious health effects. Because current screening methods for these toxins are lengthy, destructive, and costly, there is a continuous search for a more rapid, noninvasive, and cost-effective technology. The present study utilized a fluorescence excitation–emission matrix (EEM) of aflatoxin as well as two additional secondary metabolites (kojic acid and the bright greenish-yellow fluorescence (BGYF) compound) of Aspergillus flavus measured with a fluorescence spectrophotometer. The results were compared to image data acquired with a fluorescence hyperspectral sensor in order to evaluate the potential of image-based technology for detecting aflatoxin in grain. The excitation–emission matrix of aflatoxin B1 standard produced overlapping peaks in 340–400 nm of excitation range emitting in the blue range at around 450 nm. The spectral signature extracted from the hyperspectral image was also in the blue range, emitting blue fluorescence. Because the results from both systems were comparable, where all fluorescence peaks were in the blue range, the present study validates the feasibility of image-based technology for nondestructive detection of aflatoxin in corn. Additional peaks were revealed in the aflatoxin EEM in the 260-nm excitation range that were not present in the kojic acid and BGYF compound mixture. This new information allows for the separation of the aflatoxin signature from the potentially confounding overlap of other secondary metabolites occurring in the blue and blue-green spectral ranges.