Mycotoxins: Characterization , Occurrence and Detection

Mycotoxins are pharmacologically active mold metabolites produced in a strain-specific way that elicit some complicated toxicological activities (Bennett, 2003). Mycotoxins could also be described as secondary metabolites produced by a wide variety of organisms categorized as fungi, including mushrooms, yeasts and molds. The term mycotoxin was used for the first time in 1961 in the aftermath of a veterinary crisis in England, during which thousands of animals died. The disease was linked to a peanut meal, incorporated in the diet, contaminated with a toxin produced by the filamentous fungus Aspergillus flavus (Bennet & Klich, 2003; Richard, 2007). In general, mycotoxins are low-molecular-weight compounds that are synthetized during secondary metabolism by filamentous fungi; their chemical structure may range from simple C4 compounds to complex substances (Paterson & Lima, 2010).

Thousands of mycotoxins exist; more than 300 secondary metabolites have been identified while only around 30 have true toxic properties presenting significant food safety challenges (Surai, 2008). Apparently, mycotoxins have no biochemical significance on fungal growth; they may have developed to provide a defense system against insects, microorganisms, nematodes, animals and humans (Etzel, 2002). Exposure to mycotoxins may occur through ingestion, inhalation, and dermal contact, and it is almost always accidental. Most cases of mycotoxicoses (animals and humans) result from eating contaminated food. Human exposure can be direct via cereals or indirect via animal products (e.g. meat, milk and eggs) (CAST, 2003). Most mycotoxins are relatively heat-stable within the conventional food processing temperature range (80–121°C), therefore so little or no destruction occurs under normal cooking conditions, such as boiling and frying, or even following pasteurization (Milicevic et al., 2010). The stability of mycotoxins during food processing has been reviewed in the work by Bullerman & Bianchini (2007). In general, the application of a food process reduces mycotoxin concentrations significantly, but does not eliminate them completely. The food processes that have been examined include physical treatments (cleaning and milling) and thermal processing (e.g. cooking, baking, frying, roasting and extrusion). The different treatments have various effects on mycotoxins, and those that utilize the highest temperatures have the greatest effects: roasting or cooking at high temperatures (above 150 °C) appear to reduce mycotoxin concentrations significantly (Bullerman & Bianchini, 2007).

Fungi are absolutely essential to life on earth. They decompose decaying animals and vegetation, releasing nutrients. In a myriad of ways, fungi make it possible for one generation of life to sustain the next. Fungi of one species or another, or their spores, can be found virtually everywhere because they are aerobic and their spores minute in size. When the growth conditions are right for specific fungi, they will grow very rapidly into colonies, and produce toxins specific to that fungus as a by-product.

These fungal species (mycotoxins) are universal plant pathogens that are major spoilage agents of foods and feedstuffs; they occur regularly in worldwide food supplies due to mold infestation of susceptible agricultural products, causing nutritional losses in crops (in field and in storage), in particular cereals, nuts and fruit. Animal feeds produced from them is undesirable, as they are toxic and have a number of adverse effects on health, both in humans and animals thereby representing a significant hazard to the food chain.  Mycotoxins can affect the immune system, nervous system; liver, kidneys, blood and blood, and some mycotoxins are known to be carcinogens (cancer-causing).