DEVELOPMENT OF RAPID, NON-DESTRUCTIVE HYPERSPECTRAL IMAGING METHODOLOGY TO MEASURE FUNGAL GROWTH AND AFLATOXIN CONTAMINATION
Food and Feed Safety Research
2013 Annual Report
1a.Objectives (from AD-416):
Identify and quantify aflatoxin-producing fungi on corn, using a non-destructive hyperspectral imaging system. Produce spectral libraries for fungus alone and in infected corn. Determine spectral differences between different corn varieties, resistant and susceptible to aflatoxin contamination and infected and un-infected with aflatoxin producing fungi. Develop rapid, non-destructive hyperspectral imaging methodology to measure fungal growth and aflatoxin in corn kernels and spectral signatures associated with traits for resistance to fungal infection and aflatoxin contamination in corn kernels. Test system's effectiveness in laboratory and field situations.
1b.Approach (from AD-416):
Corn kernel varieties with varying levels of resistance to aflatoxin producing fungi will be collected and imaged using a tabletop hyperspectral scanning imaging system. Kernels will be spectrally analyzed to determine how much the UV, visible, and near infrared portions of the electromagnetic spectrum differ from one corn variety to another. Cultures of aflatoxin producing and non-producing fungi will also be imaged and the spectral fingerprints will be collected to produce a "spectral library" of the different strains of fungi. These data will be used to determine if hyperspectral imaging can then be used to differentiate and quantitate the varying fungal strains and/or their aflatoxin production both in pure fungal culture and in fungally infected kernels from corn varieties either resistant or susceptible to aflatoxin contamination. Techniques also will be investigated during ongoing experiments to determine the best imaging environment in which to accomplish hyperspectral analyses, such as type and direction of lighting. Once appropriate algorithms are developed, the system will be tested in various laboratory and field experiments to determine the efficacy of the system.
Lab experiments were conducted using green fluorescent protein (GFP) labeled toxigenic and atoxigenic Aspergillus (A.) flavus in order to visualize competition between the two strains. Results show a suppression of the toxin producing strain by the atoxigenic strain of the fungus. Overall, the aflatoxin signature was studied from both chemical (pure, extracted) and biological (associated with A. flavus contaminated field and lab corn) perspectives. Data from the studies were summarized in several publications and a patent "Method and Detection System for Detection of Aflatoxin in Corn with Fluorescence Spectra" was approved. Additional experiments were designed to address the detection potential of hyperspectral–based instrumentation (collecting and processing information across electromagnetic spectrum) of aflatoxin contamination on whole maize ears. A rotational stage was designed and subsequently developed to accommodate whole ears during a 360 degree rotation, producing a flat image representation of each ear. The stage was tested for image acquisition of whole maize ear data under both halogen and ultra violet (UV) illumination. In addition to maze ears, the system may be utilized for imaging other cylindrical or circular objects for food safety or related applications. This technology was developed under a grant from Bill & Melinda Gates Foundation Grand Challenge Exploration (GCE round 8), awarded in 2012. The goal of the grant is to develop portable technology to detect aflatoxin contamination in single corn ears for farmers in the developing countries. The Gates project is a joint effort between Mississippi State University and ARS-SRRC to extend knowledge gained from the collaborative project to more practical applications. Significant emphasis over this past year was placed on reviewing and summarizing data of numerous lab and field experiments previously conducted, to capture significant discoveries/concepts useful towards the aflatoxin detection/quantitation mission. This review and summary procedure was also necessary for the development of manuscripts for publication in refereed journals.