Information provided in co-operation with the Food-INFO.net website.

Mycotoxins

Moulds can appear during the growth or storage of foods. Some, although not all, moulds produce toxic substances that can cause disease or illness when eaten by humans and/or animals. These substances are called mycotoxins.

Mycotoxins are toxic (harmful) substances produced by certain moulds (filamentous fungi). Scientists first became aware of them in the early 1960s with the outbreak of turkey X disease in England. About 100.000 turkeys were killed because peanut meal in their feed was heavily contaminated with Aspergillus flavus, a mould producing mycotoxins. Other moulds that produce mycotoxins include Aspergillus, Penicillium and Fusarium. Not all of these fungi produce mycotoxins, and one mould may produce different kinds of toxins, making it difficult to generalise about their effect on human health. More than 400 mycotoxins have now been identified and their number continues to grow.

Mycotoxins can be produced when foods become infested with moulds, either during the growth period of plants or during storage. The food production process includes measures taken to prevent contamination by moulds. However, since it is difficult to keep food completely sterile, it may still have low concentrations of mycotoxins. In developed countries with temperate climates, these concentrations are usually so low that they are not dangerous. In developing countries in tropical or subtropical regions, mycotoxins occur more often and in higher concentrations because of poor storage conditions. Also, the warm and moist climate of tropical regions increases the risk of mould infection. Animal tissues may become infected with mycotoxins when the animals are fed with mould-contaminated feed.

In Europe, mycotoxins are most often found in nuts, cereals, dried fruits, fruit juices, meat products and milk. It is difficult to prevent moulds from growing on foods but their levels can be decreased by maintaining hygienic conditions during food processing and storage. Toxin-producing moulds are a particular problem in developing countries, where storage conditions may not be as controllable as in developed countries.

Mycotoxins differ greatly in terms of their toxicity and their effects on human health. The effect of mycotoxins depends on the amount and the type of toxin consumed. Research in the UK has shown that most people consume small amounts of mycotoxins in their diet without any obvious ill effects. However, high levels of mycotoxins, or frequent intakes over a long period of time can lead to severe health problems. Some mycotoxins are thought to cause cancer or tumours while others can harm the liver, kidneys, reproductive system or nervous system.

There are several ways to help destroy moulds that may be present on raw ingredients and to help prevent them developing on food products.
Stringent measures are taken during food storage and processing, to help prevent the growth of moulds. Storage conditions are particularly important. Moulds need suitable combinations of water, nutrients, temperatures and acidity to grow and multiply. Their growth can be prevented by controlling these and other factors. For example, heating for a sufficient period of time kills moulds so many food processing techniques including pasteurisation and canning help to remove any moulds that may be present. Drying food removes the moisture needed for moulds to grow while, reducing the storage temperature or making the product more acid helps to prevent mould growth.

Most moulds are heat-sensitive and are destroyed by pasteurisation. Some kinds of mould however are resistant to heat. These are found mostly in fruit, fruit products or raw materials derived from fruit (e.g. pectin) and need temperatures of 100 degrees or higher to be destroyed. Although this heat treatment works well for the mould itself, many mycotoxins are not, or are only partly, broken down by pasteurisation or sterilisation.

Moulds are visible if they grow on top of the food however if they grow inside the food, they can be difficult to see. The mycotoxins themselves cannot be seen.

Mycotoxins differ in their origins and overall effects on health. The most common mycotoxins are :

Aflatoxins
Ochratoxin
Trichotecenes
Zearalenone
 

The following table shows a larger number of common and less-common toxins produced by various moulds. Most of these do not pose a health effect in humans. Beware: not all of these are food-related, even though the fungi may be present in food.

This article was written in co-operation with the Food-Info.net website, an initiative of the Wageningen University, The Netherlands . We gratefully thank the authors behind the Food-Info website for providing us with the information for this article. For further information please visit http://www.food-info.net.