What is Aflatoxin?

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Have you ever heard of aflatoxin? It's not a commonly known toxin, but it is a very deadly one. It can affect humans, horses, and every other mammal on the planet. This lesson describes what aflatoxin is, where it's found, and how it can be spotted and prevented.

A Deadly Toxin in our Food

Is the food you eat really safe? There is one particular toxin that can contaminate some of the foods people love the most, including corn, peanuts, tree nuts, and many others. Exposure to this toxin can cause a quick and painful death or even cancer, depending on how much is eaten and over what period of time. Here we'll describe its name, what it contaminates, how it can be spotted, and how it can be prevented.

What is Aflatoxin?

Aspergillus flavus (as well as Aspergillus parasiticus) is an opportunistic crop pathogen, also known as a mold fungus. It is actually a very common soil fungus. The main problem for agriculture, people, and animals arises when it produces carcinogenic (cancer-causing) and poisonous toxins called aflatoxins. These toxins are secondary metabolites (intermediates and products of metabolism) found in crop seeds before and after harvest.

Aspergillus flavus, a cause of aflatoxin.

Unlike primary metabolites, secondary metabolites do not play a significant role in an organism's growth, reproduction, or development but may have important functions for an organism's survival (for example, natural antibiotics are secondary metabolites and act as weapons against bacteria). It is not clear why Aspergillus produce aflatoxins but, like antibiotics, they may serve as a kind of chemical warfare weapon that confers a survival advantage to the fungus.

Spotting Aflatoxin

Although Aspergillus flavus can grow on just about any crop seed, it's more commonly found on oilseed crops such as corn, cottonseed, peanuts, and tree nuts. Sorghum, wheat, (sweet) potatoes, and rice can be affected as well. Aspergillus flavus can be recognized by its olive-green or gray-green colors on corn kernels. The presence of mold does not mean aflatoxins have been produced. However, the more damaged and moldy the corn is, the higher the likelihood that aflatoxin contamination has occurred.

Preventing Aflatoxin

The prime conditions for aflatoxin production in pre-harvest corn include hot (ideally 77F - 95F), dry summers, where the nights are warmer than 70F, and the kernel moisture is between 18%-20%. To prevent aflatoxin development after harvest, stored kernels should ideally be clean (e.g. no visibly moldy corn) and undamaged (since fungi infect damaged kernels more easily). Corn stored for the long term should be dried to no more than 14% moisture, because toxin production stops around 15% moisture. Optimally, corn should be stored at 35F-40F in the winter and 50F-60F in the summer. This is because aflatoxin production has been noted to occur, albeit not as commonly, at temperatures as low as 52F.

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