New Test for Aflatoxin-Fighting Corn

Corn kernels may someday produce ample amounts of their own anti-fungal compounds that prevent aflatoxin contamination when the grain is stored. When the fungus Aspergillus flavus invades corn kernels, it produces aflatoxin, a carcinogen.

ARS scientists are employing a new test to quickly identify anti-fungal compounds naturally produced in corn kernels. The test involves growing the fungus on a thin layer of nutrient medium suspended on a glass fiber disk in a vial. Previous methods, which used more of the nutrient medium, required more solvent to extract the toxin.

So far, Agricultural Research Service chemist Robert A. Norton has identified a half-dozen promising aflatoxin inhibitors, including alpha carotene and several other carotenoids--compounds that impart yellow color to modern corn hybrids.

The new assay is a significant improvement over older, slower testing methods. Scientists at the National Center for Agricultural Research Utilization in Peoria, Ill., can now test up to 200 samples a week, and from a much wider range of compounds. The research parallels efforts to breed corn that supports less growth of the fungus.

In the United States, corn with more than 20 parts per billion (ppb) of aflatoxin-- equivalent to just 1 ounce in 3,125 tons--is considered unfit for feeding to animals that produce meat or milk for humans. Grain with more than 5 ppb can't be used for making food-grade corn products.

Details are in a story in the July issue of ARS' Agricultural Research magazine. The story is also on the World Wide Web at:

http://www.ars.usda.gov/is/AR/archive/jul98/afla0798.htm

Scientific contact: Robert A. Norton, USDA-ARS National Center for Agricultural Utilization Research, 1815 N. University Street, Peoria, IL 61604; phone (309) 681-6251, fax number (309) 681- 6693, e-mail nortonra@mail.ncaur.usda.gov