Mycotoxins: genesis, metabolism and toxicology

NIC-AL Snc is able to provide a valid external support to all the professional profiles involved in mycotoxins and aflatoxins management. Our skills are both analytical and advisory:

  1. Analysis of food and feed by means of immunoassays kit and analytical chemistry techniques  (HPLC);
  2. Results managenent according to the competent authorities and in material handling;
  3. Scheduling of procedures and self control plans for global management of mycotoxin problem both in emergency and ordinarytimes.

Mycotoxins, literally, are toxic substances produced by fungi: these can be divided into two main categories according to the fungal species responsible for their genesis.

Macromycetes (mushrooms more common meaning of the term) produce mycotoxins such as Amantina or muscarine that cause the classic poisoning phenomena associated with human consumption; the micromycetes (molds) produce aflatoxin, fumonisin and tricoteni liable for acute and/or chronic toxicity phenomena caused by contamination of food and feed.

In the food sector aflatoxins are the most important because of their potential and massive spread on different matrices; these are the products of secondary metabolism of some fungal strains of "Aspergillus flavus" (hence the term aflatoxin) and "Aspergillus parastiticus". These molds grow on substrates such as grains (mostly maize), oilseeds (peanut in particular), spices, and dried fruit both during cultivation, harvest and storage. In case of particular environmental conditions, i.e. temperatures between 25 ° C and 32 ° C and water activity between 0.82 and 0.87 there are the best conditions for their development.

The most dangerous aflatoxins (both for transmission and for toxicity) are B1, B2, G1, G2. Aflatoxin B1 is considered genotoxic and epatocancerogena and, since 1993, is included in the group of "carcinogenic to humans" by the International Agency for Research on Cancer. The peculiarity of being genotoxic makes impossible to establish a minimum level of intake and therefore the toxicological reference principle is to maintain the lowest possible level of exposure (as low as reasonable achievable ALARA).

In the livestock industry, the spread of aflatoxins, especially in the feed used for cattle, leads to the formation of a number of metabolites mainly found in milk. Among these the most relevant to public health is aflatoxin M1 (which derives its name from milk) which is unique among the metabolites of B1, to pass in significant quantities in the milk; its hepatocarcinogenic power is lower and lies between 2% and 10% compared to that of aflatoxin B1. The genesis of aflatoxin M1 in milk is usually quick: in case of ingestion of high amounts of aflatoxin B1 it already appears in milk after 4 hours; just as fast is its disappearance from milk: on average, already within 3-4 days after discontinuation of B1.

Aflatoxins, as all mycotoxins, are thermostable then the heat treatment normally used in industrial transformation processes are not able to reduce previous levels of contamination.

Strategies and guidelines to contain the levels of contamination by aflatoxins are based on a series of actions to be taken along the food chain.

As regards, for example, corn (foodstuff directly involved in the aflatoxin M1 in milk) there are several preventive actions that allow a significant reduction of the risks of contamination level, especially, in primary production:

  • Harvesting of the product, depending on the month, at relative humidity levels of between 25% and 27%, never less than 22%;
  • decrease in the permanence of the corn in the field after its physiological maturity;
  • use of a mechanical collection process that the grains of the broken limits and eliminate the greatest amount of impurities as possible;
  • reduction of the time between harvest and drying, avoiding to use excessively drastic processes with thermal shock that may cause cracks and microcracks, preferential ways of attack of funginie spores during storage;
  • removal of smaller and light parts and broken kernels.

Obviously, in addition to these preventive steps it is important to perform any analytical control of feed and milk product in order to check out the different trends of aflatoxins B1 and M1 and to be able to take appropriate preventive action before exceeding the regulatory limits in force.

Considering the criticality of mycotoxins on human health, there are legal provisions in European Community that set strict limits on the various types of food products for human use (EC Regulation 1881/2006) and for animal feed (EC Regulation 574/2011).

 These provisions also prohibit the use of chemical agents for the decontamination of contaminated products, prohibit the possibility of mixing compliant with non-compliant batches and fix tolerable limits both on finished products and raw materials. In contrast to the European legislation, which has as its main objective the protection of public health, the laws in force in the United States of America establish tolerable levels based solely on commercial evaluations without considering in any way the risk factors for human or livestock consumption. This results in maximum limits, such as aflatoxin M1 in milk ten times greater (0.5 mg/kg USA, 0.050 mg/kg EU).

The current critical situation has led to the definition of warning limits (0.040 mg/kg) for the content of aflatoxin M1 into milk in the first place defined by the Lombardy Region; the aim is indeed to have legal instruments to allow action before they are exceeded the maximum levels set by law (0.050 mg/kg).