Aflatoxin

Aflatoxin is an undesirable byproduct of certain species of fungi of the genus aspergillus, (basically two species cause the problem in the USA, aspergillus flavus, and aspergillus parasiticus, but there are dozens more world-wide).  Physically, aspergillus often looks like a green mold when present on grain; however, aflatoxin itself is not visible to the naked eye.

The presence of an aspergillis fungus on grain does not necessarily indicate the presence of aflatoxin, since aflatoxin is not always produced just because the fungus is present.  On the other hand, aflatoxin may be present, even though no outward indications of fungus are readily apparent to the naked eye.

Aflatoxin is one of several micotoxins, (or mycotoxins), that can contaminate corn, (maize), peanuts, cottonseed, occasionally milo, and possibly other commodities that experience adverse weather conditions during critical stages of the growing season, or that are improperly stored..

The greatest risk for the development of aflatoxin occurs during major droughts.   It can also develop, or intensify in susceptible commodities that are stored improperly.  Commodities that have been dried to below about 12-1/2 percent moisture are generally considered stable, and immune to any risk of additional aflatoxin development.  Susceptible grain or seeds that are allowed to get wet during storage, may develop aflatoxin, or may show an increase in aflatoxin levels, if the product already contained aflatoxin before being placed into storage.  Aflatoxin levels generally cannot be accurately accessed in grain or seed at moisture levels above about 18 percent.   As the moisture level is decreased, any aflatoxin present can be readily detected by conventional testing methods.

Detection of aflatoxin, and quantitative analysis of the amounts present in a sample, requires a laboratory test using a properly performed testing procedure, and carefully calibrated equipment.  There are a number of techniques, and kits are available on the market, ranging from economical screening tests which yield a simple pass or fail result, to sophisticated units that cost many thousands of dollars, and, (presumably), produce an accurate determination of the level of aflatoxin present in a sample.

Since the grain or seed must be liquefied before it can be tested, it is obvious that all of the product cannot be tested, else there would be nothing left to use after the test is competed.  Instead, a representative sample is drawn from the lot, and the sample is tested.  The results of the test are assumed to accurately reflect the condition of the lot from which the sample was taken.  (Sometimes this amounts to a questionable assumption).

This sampling procedure is undoubtedly the most critical part of the entire testing procedure.  Obtaining a sample that is truly representative of the total quantity from which it is taken is much easier said than done.  Testing for any component that exists in the range of a few parts per billion is truly like searching for the proverbial needle in the haystack.  The inability to be able to easily and consistently obtain a truly representative sample is the Achilles heel of current aflatoxin testing methods, and quite often, a dozen tests on the same lot of product will yield a dozen different results, sometimes over a ridiculously wide range of numbers.  Be that as it may, it is the only "official" game in town, for the present.

The once popular testing method of observing a sample under a black light, and counting the "sparkles" present, yields results of questionable value, since it detects kojic acid, (another byproduct of aspergillus), rather than aflatoxin.  Though kojic acid is often present when aflatoxin is present in a sample, there are instances where kojic acid is present in significant quantity without any significant presence of aflatoxin, and there are instances where significant quantities of aflatoxin are present, without a significant presence of kojic acid.