Food Safety: Mycotoxins

Mycotoxins are compounds produced by moulds under specific environmental conditions. These toxins are harmful to human and animal health. Some of the most important mycotoxins are shown in Table 1.

 

In Canada, the mycotoxins of major concern are:
     • deoxynivalenol (DON)
     • T-2 toxin
     • zearalenone
     • fumonisin B1
     • ochratoxin A

Aflatoxins are also of concern in food products imported from warmer tropical and subtropical regions.

Why are mycotoxins important?

Mycotoxins are important because they can be costly when they affect:
     • animal productivity
     • human health
     • international trade

The Food and Agriculture Organization of the United Nations (FAO) states the cost of mycotoxins in Canada and United States is approximately $5 billion a year.

When are mycotoxins produced?

Mould contamination usually occurs in the field. Mycotoxins can develop at various stages:
     • pre-harvest growth
     • harvest
     • storage

For example, Fusarium spp. can produce toxins in the field and during harvest. Other toxins can be produced during storage by Aspergillus and Penicillium species (Abramson et al., 1997).

Foods affected by mycotoxins

Mycotoxins occur in a wide a variety of foods and feeds. The food crops most often affected are corn, peanuts, cottonseed, sorghum, wheat, corn, barley, coffee, cocoa and tree nuts (pecan, almond, pistachio, hazelnut, walnut and Brazil nut). They have also been found in rice, beer and wine. In Canada, mycotoxins occur mainly in cereal grains and corn, but have been reported in other crops such as alfalfa and oilseed. Table 2 shows a summary of the food products susceptible to specific mycotoxins.


Table 2. Food products susceptible to specific mycotoxins

Adapted from Calvo, 2005.


Mould capable of producing mycotoxins can grow in a variety of places and under several environmental conditions. The most important factors for mycotoxin production are moisture content, relative humidity, temperature and pests. In general, high moisture content (20 to 25%), high relative humidity (70 to 90%) and warm temperatures (22 to 30°C) enhance mould growth and toxin production. Insects and mites can also produce physical damage on the kernel predisposing it for mould invasion and toxin production.

Most mould is naturally occurring and is found in soil and air. It is difficult to prevent contact with agriculture commodities. However, the factors that affect growth and toxin production may be controlled.

Most mycotoxins are very stable. They can resist high temperatures and several manufacturing processes. For example, zearalenone is stable during storage, milling and cooking (Gajecki, 2002). DON and T-2 toxin are stable at 120°C and relatively stable at 180°C (Kamimura, 1989). Although, cooking can reduce the levels of certain mycotoxins in food products, it does not achieve complete detoxification. It is not surprising to detect low content of mycotoxins in processed foods. This is why it is important to prevent the formation of toxins in raw material.

Health Implications

Mycotoxins can cause different toxic effects depending on the type of toxin and the dosage. High doses of mycotoxin can cause acute illness or death; low doses cause chronic toxicity. The toxicity of mycotoxins may affect the body's nervous, heart, lungs and digestive tract. Mycotoxins are also associated with acute hepatitis and liver cancer.


Detection

Food products need to be tested for mycotoxins:
     • to meet regulatory guidelines
     • to reduce the risks of mycotoxin contamination
     • to maintain product quality

Mycotoxins cannot be detected visually, have no specific taste or smell in contaminated food. This makes it difficult to identify an infected crop. Analytical tests are the main tool for toxin detection. Table 3 indicates some of the available tests.

ELISA, enzyme-linked immunosorbent assays
TLC, thin-layer chromatography
HPLC, high-performance liquid chromatography
GC, gas chromatography
LC, liquid chromatography
MS, mass spectrometry
FILIA, flow-injection liposome immunoanalysis

ELISA test kits are commercially available (ex: R-Biopharm, Biotrace International, Neogen Corporation, Elisa Technologies).

More information on mycotoxin testing can be found in the Aflatoxin Handbook developed by the Federal Grain Inspection Service (USDA).

Prevention and Control

Mycotoxins are difficult, and sometimes impossible to eliminate. The best control is prevention. The production can be prevented by reducing the moisture content of food products and controlling storage conditions such as temperature and/or relative humidity. In general, reducing moisture content to the equivalent of less than 0.70 water activity (<14.5% moisture by weight) prevents mould growth and mycotoxins.

The Canadian Food Inspection Agency (CFIA) recommends the following management practices to minimize mycotoxin contamination:

• Limit bird and insect damage. Damaged kernels are easily contaminated with mould.

• Harvest grain as soon as possible to reduce high moisture conditions. Mould grows better under high moisture environment.

• Dry grain. Low moisture conditions prevent mould growth and mycotoxin production post-harvest.

• Ensure silo conditions remain oxygen free (anaerobic conditions) to limit mould growth and mycotoxin contamination. Mould cannot grow under truly anaerobic conditions.

• Use crop rotation to minimize the carry-over of moulds from one year to the next.

• Avoid planting crops that may be susceptible to mould adjacent fields where the disease may spread from one crop to the other.

• Grain handlers should use masks to avoid inhalation and ingestion of dust. Mould spores and mycotoxins are often concentrated in the fines and dust of grains.

Hazard Analysis Critical Control Points (HACCP) offers a suitable approach to control mycotoxins by preventing their formation. The Manual on the Application of the HACCP System in Mycotoxin Prevention and Control, published by FAO in 2001, provides an overview and examples on the application of HACCP to mycotoxin control.

Regulations and Guidelines

Currently, more than 100 countries have mycotoxin regulations for food and/or feed. Canada and the United States have had mycotoxin regulations in place for many years. Recommended tolerances for several mycotoxins can be found on the CFIA website.

For more information on worldwide regulations, see FAO publication Worldwide Regulations for Mycotoxins in Food and Feed in 2003.