Technical Note: Characteristics and Sorting of White Food Corn Contaminated with Mycotoxins

Authors: Pearson, Thomas; Wicklow, Donald; Brabec, Daniel - Dan

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2009
Publication Date: 1/1/2010
Citation: Pearson, T.C., Wicklow, D.T., Brabec, D.L. 2010. Technical Note: Characteristics and Sorting of White Food Corn Contaminated with Mycotoxins. Applied Engineering in Agriculture. 26(1):109-113.

Interpretive Summary: Mycotoxins are know carcinogens that can be found in grain, nuts, and cottonseed due to fungal infection in the field. Food having mycotoxins above FDA guidelines cannot be traded across state borders and result in lost revenue for farmers and grain handlers. Mycotoxins are produced by naturally occuring fungi and tend to infect drought stressed or damaged kernels in the field. This study identified characteristics of white corn having fungal damage and mycotoxins. Futhermore, we tested the fesibility of separating corn kernels having high levels of mycotoxins from those with low or no mycotoxins using commercially available sorting machines. For white corn, it was found that after two passes through a commercially available high speed optical sorter, aflatoxin (one of the more common mycotoxins) could be reduced by an average of 88%. Approximately half of the aflatoxin contaminated kernels missed by the optical sorter were larger, asymptomatic kernels with cracks in their outer skin. The remaining aflatoxin was found in smaller kernels damaged from insect feeding, many without germs.

Technical Abstract: Samples of white corn grown in southern Texas were collected for characterization and sorting of kernels containing mycotoxins. Kernels were grouped into one of six symptom categories depending on the degree of visible discoloration and bright green-yellow fluorescence (BGYF) or bright orange fluorescence (BOF). Kernels visibly discolored (greater than or equal to 25% of their surface) and having BGYF contained over 57% of the aflatoxin. However, kernels approximately 50% discolored without BGYF contained over 35% of the aflatoxin. Over 33% of the fumonisin was found in kernels that were visibly discolored and had BOF. The remaining fumonisin was in asymptomatic kernels at low levels. Sorting tests for removing mycotoxin contaminated kernels were performed using a dual wavelength high speed commercial sorter. In one pass through the sorter, aflatoxin was reduced by an average of 46%, and fumonisin was reduced by 57% while removing four to nine percent of the corn. Re-sorting accepted kernels a second time resulted in an 88% reduction in aflatoxin while removing approximately 13% of the corn. Approximately half of the aflatoxin missed by the optical sorter was found in larger, asymptomatic BGYF kernels, with the remaining aflatoxin in smaller kernels damaged from insect feeding, many without germs.