Location: Food and Feed Safety Research
Title: Detecting corn inoculated with toxigenic and atoxigenic fungal strains with fluorescence hyperspectral imagery Authors
Submitted to: Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 8, 2013
Publication Date: June 13, 2013
Citation: Yao, H., Hruska, Z., Kincaid, R., Brown, R.L., Bhatnagar, D., Cleveland, T.E. 2013. Detecting corn inoculated with toxigenic and atoxigenic fungal strains with fluorescence hyperspectral imagery. Biosystems Engineering. 115:125-135. Interpretive Summary: Aflatoxins are poisons produced by the fungus Aspergillus flavus after it infects agricultural commodities such as corn. Since aflatoxins in food and feed are regulated, enhanced ability to detect and measure fungal growth and aflatoxin contamination of corn could contribute significantly towards the separation of contaminated from healthy grain. A collaboration between ARS-SRRC, Food and Feed Safety Research Unit and Mississippi State University, Stennis Space Center, MS is exploring the use of hyperspectral imaging non-destructive technology to detect mycotoxin-producing fungi in grain products. The objective of the current study was to assess, with the use of a hyperspectral sensor, the difference in fluorescence emission between corn kernels inoculated in the field with toxigenic or atoxigenic Aspergillus flavus strains. After harvest, kernels were examined on the “germ” side and on the “endosperm” side, however, the “germ” side showing the best results. Contaminated kernels all had longer peak wavelengths than did healthy ones. Further experiments may lead to this technology being used to rapidly and accurately detect/measure Aspergillus flavus infection/aflatoxin contamination of corn without destruction of healthy grain. This could provide a useful tool to both growers and buyers in the corn industry that could enhance protection of food and feed as well as increase profits.
Technical Abstract: Naturally occurring Aspergillus flavus strains can be either toxigenic or atoxigenic, indicating their ability to produce aflatoxin or not, under specific conditions. Corn contaminated with toxigenic strains of A. flavus can result in great losses to the agricultural industry and pose threats to public health. Past research showed that fluorescence hyperspectral imaging could be a potential tool for rapid and non-invasive detection of aflatoxin contaminated corn. The objective of the current study was to assess, with the use of a hyperspectral sensor, the difference in fluorescence emission between corn kernels inoculated with toxigenic and atoxigenic inoculums of A. flavus. Corn ears were inoculated with AF13, a toxigenic strain of A. flavus, and AF38, an atoxigenic strain of A. flavus, at dough stage of development and harvested 8 weeks after inoculation. After harvest, single corn kernels were divided into three groups prior to imaging: control, adjacent, and glowing. Both sides of the kernel, germ and endosperm, were imaged separately using a fluorescence hyperspectral imaging system. After imaging all samples were processed for single kernel assay with affinity column fluorometry followed by discriminant analysis classification. Results from discriminant analysis of the imaging data found that the classification accuracies of the three visually designated groups were not promising. However, the separation of corn kernels based on different fungal inocula yielded better results. The best results were achieved with the germ side of the corn kernels. Results from the chemical data followed a similar trend as did the image data. The kernels were grouped into ‘contaminated’ and ‘healthy’ with 20 ppb and 100 ppb thresholds, taking into consideration side (germ and endo), and the corresponding spectra were analyzed. The contaminated corn kernels all had longer peak wavelength than did the healthy ones. Results from the discriminant analysis classification indicated overall higher classification accuracy for the 100 ppb threshold on the germ side (94.4%). The germ side was also more useful at discriminating healthy from contaminated kernels for the 20 ppb threshold. Overall, the results from the present study enhanced the potential of fluorescence hyperspectral imaging for the detection of aflatoxin contaminated corn.