Detecting aflatoxin in single corn kernels by transmittance and reflectance spectroscopy

Transmittance spectra (500 to 950 nm) and reflectance spectra (550 to 1700 nm) were analyzed to determine if they could be used to distinguish aflatoxin contamination in single whole corn kernels. Spectra were obtained on whole com kernels exhibiting various levels of bright greenish-yellow fluorescence. Afterwards, each kernel was analyzed for aflatoxin following the USDA-FGIS Aflatest affinity chromatography procedures. Spectra were analyzed using discriminant analysis and partial least squares regression. More than 95% of the kernels were correctly classified as containing either high (> 100 ppb) or low (< 10 ppb) levels of aflatoxin. Classification accuracy for kernels between 10 and 100 ppb was only about 25%, but these kernels do not usually affect total sample concentrations and are not as important. Results were similar when using either transmittance or reflectance, and when using either discriminant analysis or partial least squares regression. The two-feature discriminant analysis of transmittance data gave the best results. However for automated high-speed detection and sorting, instrumentation that uses single-feature reflectance spectra may be more practically implemented. This technology should provide the corn industry with a valuable tool for rapidly detecting aflatoxin in com.