New Tests Nab Toxins

By Linda McGraw
February 16, 1999

New tools to detect mycotoxins that contaminate corn, barley, wheat and other commodities have been developed by an Agricultural Research Service scientist. ARS is USDA’s chief scientific research agency.

Fungi that grow on these crops produce the toxins. One of the more harmful ones is aflatoxin, produced by the fungus Aspergillusflavus. Aflatoxin takes its greatest toll on U.S. corn production during drought and excessively high temperatures.

Law prohibits the sale of corn--or any grain--for human consumption if it contains more than 20 parts per billion of aflatoxin. For domestic non-milk-producing animals, the permissible level ranges from 100 to 300 ppb.

Inspectors need accurate and sensitive tests to detect such minute levels. That’s why ARS chemist Chris M. Maragos in Peoria, Ill., has developed several new tests that more accurately detect the toxin.

One is a new antibody for an existing ELISA test (enzyme-linked immunosorbent assay). The antibody selectively binds with aflatoxin. If the sample is free of aflatoxin, the technician sees a deep orange color. If toxin is present, there is no color.

Another tool, capillary electrophoresis, separates compounds based on their electrical charge. This test doesn’t require chemical solvents used by traditional analytical methods. Maragos adapted capillary electrophoresis to measure another type of mycotoxin--deoxynivalenol, commonly called vomitoxin, or DON. DON is associated with wheat scab, a problem that has cost wheat growers around $3 billion in losses over the last 3 years.

An article describing the tests appears in the February issue of ARS’ Agricultural Research magazine. The story is also on the World Wide Web at:

/is/AR/archive/feb99/toxin0299.htm

Scientific contact: Chris M. Maragos, ARS National Center for Agricultural Utilization Research, Peoria, Ill., phone (309) 681-6686, fax (309) 681-6686, maragocm@mail.ncaur.usda.gov.