Submitted to: Journal of Food Additives & Contaminants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 3, 2009
Publication Date: May 10, 2010
Citation: Yao, H., Hruska, Z., Kincaid, R., Brown, R.L., Cleveland, T.E., Bhatnagar, D. 2010. Correlation and Classification of Single Kernel Fluorescence Hyperspectral Data with Aflatoxin Concentration in Corn Kernels Inoculated with Aspergillus flavus Spores. Journal of Food Additives & Contaminants. 27(5):701-709. 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 quantify aflatoxin content of corn kernels. The objective of this study was to examine the relationship between fluorescence emitted from corn kernels inoculated with Aspergillus flavus and aflatoxin levels within the kernels. Highly contaminated kernels were found to have a lower fluorescence peak than less contaminated kernels. Overall, our results indicate that fluorescence hyperspectral imaging may be applicable in estimating aflatoxin content in individual corn kernels. 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: The objective of this study was to examine the relationship between fluorescence emissions of corn kernels inoculated with Aspergillus flavus and aflatoxin contamination levels within the kernels. The choice of methodology was based on the principle that many biological materials exhibit fluorescence emission responses under an excitation light source such as an ultraviolet light. Aflatoxin contaminated corn kernels were produced through artificial inoculation of corn ears in the field with toxigenic A. flavus spores. The kernel fluorescence emission data was taken with a fluorescence hyperspectral imaging system when corn kernels were excited with 365 nm UV light with 500 ms integration time. Raw fluorescence image data were preprocessed and regions of interest (ROI) in each image were created for all kernels. The ROIs were used to extract spectral signatures and statistical information. The aflatoxin contamination level of single corn kernels was then chemically measured using affinity column chromatography. A Fluorescence Peak Shift (FPS) phenomenon was noted among different groups of kernels with different aflatoxin contamination levels. The FPS was found to move more toward longer wavelength in the blue region for the highly contaminated kernels and toward the shorter wavelengths for the clean kernels. Highly contaminated kernels were also found to have a lower fluorescence peak magnitude compared with the less contaminated kernels. It was also noted that a general negative correlation exists between measured aflatoxin and the fluorescence image bands in the blue and green regions. The correlation coefficients of determination, r**2, was 0.72 for the multiple linear regression model. The multivariate analysis of variance found that the fluorescence means of four aflatoxin groups, < 1 ng/g, 1-20 ng/g, 20-100 ng/g, and is equal to or greater than 100 ng/g, were significantly different from each other at 0.01 level of alpha. Classification accuracy under a two-class schema ranged from 0.84 to 0.91 when either a threshold of 20 ng/g (parts per billion) or 100 ng/g was used. Overall, our results indicate that fluorescence hyperspectral imaging may be applicable in estimating aflatoxin content in individual corn kernels.