IDENTIFICATION OF FOURIER-TRANSFORM INFRARED PHOTOACOUSTIC SPECTRAL FEATURES FOR DETECTION OF ASPERGILLUS-FLAVUS INFECTION IN CORN

Aspergillus flavus and other pathogenic fungi display typical infrared spectra which differ significantly from spectra of substrate material s such as corn. On this basis, specific spectral features have been id entified which permit detection of fungal infection on the surface of corn kernels by photoacoustic infrared spectroscopy. In a blind study, ten corn kernels showing bright greenish yellow fluorescence (BGYF) i n the germ or endosperm and ten BGYF-negative kernels were correctly c lassified as infected or not infected by Fourier transform infrared ph otoacoustic spectroscopy. Earlier studies have shown that BGYF-positiv e kernels contain the bulk of the aflatoxin contaminating grain at har vest. Ten major spectral features, identified by visual inspection of the photoacoustic spectra of A. flavus mycelium grown in culture versu s uninfected corn, were interpreted and assigned by theoretical compar isons of the relative chemical compositions of fungi and corn. The spe ctral features can be built into either empirical or knowledge-based c omputer models (expert systems) for automatic infrared detection and s egregation of grains or kernels containing aflatoxin from the food and feed supply. (C) 1997 Elsevier Science B.V.