Technical Talk: Mitigating the Mycotoxin Risk

This column is written by Dr. John Michaelides of the Guelph Food Technology Centre.

Question: What are mycotoxins, how do they contaminate grains and other food ingredients, what are the regulatory limits, and how can we reduce them in our baked goods?

Answer: Mycotoxins are chemical compounds produced by fungi that are toxic or in some cases carcinogenic; these toxins affect both human and animal health. Mycotoxin-producing fungi can be found on grains, fruits, vegetables and other organic materials.

Mycotoxins can severely affect our food supply with devastating consequences to human and animal health. Effects of mycotoxins are numerous and diverse including: liver, kidney and reproductive dysfunction; impacts on the immune and nervous systems; cancer and ultimately death. Mycotoxins are very powerful and their presence in minute concentrations (parts per million and in some cases in parts per billion) in food or feed is considered a health
hazard.

Mycotoxins have been associated with human suffering for millennia. With no way to explain the source of the suffering humans attributed the deadly effects of mycotoxins to gods and holy entities. For example, ergotism, which is the term used to describe the severe symptoms that occur after ingesting grain contaminated with ergot, was often called St. Anthony’s fire or holy fire due to the hallucinogenic effects the toxin produced. In the middle ages, if a fungal outbreak in grain was severe, ergotism was known to have killed thousands of Europeans. Ergot is actually a structure called a sclerotium that resembles the grain kernel of rye but is much darker in colour and made out of the filaments of the fungus Claviceps purpurea. These structures contain many mycotoxins, among them lysergic acid diethylamide – more commonly known as LSD. Ergot was the first mycotoxin problem that affected the millers and bakers through the middle ages. Today, the ergot problem is not as significant thanks to the grain handling industry.

Mycotoxin poisonings have probably occurred for as long as humans have inhabited the earth. However, only recently has it been possible to isolate and characterize these chemical compounds and associate them with the symptoms of the poisonings. With this newfound understanding many mycotoxins have been identified and their toxicity has been evaluated in humans and animals.

In Canada, and other temperate climates, the major mycotoxins produced by indigenous fungi are the trichothecenes which include deoxynivalenol (DON or Vomitoxin), nivalenol (NIV), T-2 toxin, and HT-2 toxin. Others include zearalenone (ZEN), fumonisin B1 (FB1), ochratoxin A (OA) and ergot.

However, as our trade policies become more liberal, other mycotoxins of concern may be introduced into the Canadian food and feed supply from warmer or subtropical climates. For example the fungus Aspergillus flavus, which produces aflatoxin, is not indigenous to Canada, however importation of foods, feed or ingredients from warmer climates can result in contamination of our foods with this toxin.

The major concern with mycotoxins in the baking industry is the contamination of flour. Traditional milling processes may reduce the amount of mycotoxins in the refined flour. However, as we move towards including more whole grains in baked goods the threat of contamination should be taken more seriously. It is estimated that 25 per cent of the grains produced each year worldwide are contaminated with mycotoxins.

Exposure to mycotoxins, for humans, is mainly through the consumption of contaminated foods but it can also occur through inhalation and skin absorption.

There are many ways to prevent or minimize the contamination of crops with mycotoxin-producing fungi. Farmers can implement crop rotations, use fungicides and alter harvesting practices, as well as improve grain handling and storage. In addition there is an attempt to develop wheat and other grain varieties that are resistant to fungal infection.

Many countries around the world (approximately 100 in 2003) have regulations in place to deal with mycotoxin contamination of feed and food. The Canadian Food Inspection Agency has introduced limits and tolerance levels for certain mycotoxins in foods and ingredients for human consumption as well as animal feed. For example, Deoxynivalenol (DON) has a limit of two parts per million (mg/kg) in unclean soft wheat for human consumption. The limit for Aflatoxin in nut products destined for human consumption is 15 parts per billion. More information on Canadian limits and tolerance levels can be found on the CFIA website.

Mycotoxin contamination of food and feed is a serious problem but concerted efforts by governments and industry reduce the risk of contamination of our food supply. As the market moves towards organic and natural products we need to take the necessary measures in order to minimize the mycotoxin risks associated with these products.

For more information, or fee for service help with product or process development needs, please contact the GFTC at 519-821-1246, by fax at 519-836-1281, or by e-mail at gftc@gftc.ca.