Aflatoxins are produced by the secondary metabolism (i.e. the metabolism induced in a plant organism by external factors) of some species of filamentous microfungi such as, for example,Aspergillus flavus and Aspergillus parasiticus. They can develop during cultivation, harvesting and storage on numerous products of vegetable origin such as cereals (with particular reference to corn), oil seeds (such as peanuts), spices, grains, dried and dried fruit.
Among the 17 types of aflatoxins identified so far, only five are considered important for their diffusion and toxicity: aflatoxins B1, B2, G1, G2 and aflatoxin M1.
The geographical distribution of the aflatoxin-producing fungi species shows their adaptation to hot / humid and very dry weather conditions. Crops from tropical and / or subtropical areas are, in fact, more frequently and severely contaminated but due to climate change also crops present in areas that currently have a temperate or cold climate could be affected in the future.Risks to health
Risks to health
Aflatoxins have the ability to cause damage to health (toxicity) both in the short-medium term and chronic. The liver is the main target of aflatoxins: the one of greatest toxicological interest is undoubtedly aflatoxin B1 (AFB1) because it has an action on genes (genotoxic) and on the development of liver cancer (hepatocarcinogenic). In 1993, the International Agency for Research on Cancer classified aflatoxin B1 in Group 1, namely as carcinogen for humans.
Among the metabolic transformation products of aflatoxin B1 (i.e. the transformations that make a substance taken by the body better assimilable or more easily eliminated), the most important for health is aflatoxin M1, a molecule that is found essentially in the milk from cattle, sheep and goats and is more easily transportable through the bloodstream. Its power to cause liver cancer is between 2 and 10% of that of type B1.
Exposure occurs mainly through food, but can also take place by inhalation and by contact with the skin, especially in the workplace (for example, feed mill operators).Limits imposed by the European Union
Limits imposed by the European Union
At European level, Regulation (EU) 1881/2006 (consolidated text) sets the maximum limits that may be present in food products such as cereals, dried fruit, spices, baby products and milk as regards aflatoxin B1, the total aflatoxins, (AFB1 + AFB2 + AFG1 + AFG2) and the "aflatoxin M1.
The criteria followed in the Regulations to determine the maximum permitted levels of aflatoxin are essentially based on the difference between foods intended for human use that require physical treatments to reduce aflatoxin before the food is fit for consumption, and ready-made food products. Furthermore, to ensure a high level of safety of all ingredients in the food supply chains, European laws prohibit both the use of chemical agents to eliminate aflatoxins from contaminated products, and the possibility of mixing batches of compliant foods. with the maximum levels of aflatoxins established with those which, on the other hand, are not. It should also be noted that the maximum tolerable limits have been set both on the finished product and on the individual ingredients.
In the zootechnical sector, Regulation (EU) 574/2011, which amended the Community Directive 2002/32 on undesirable substances in feed, sets the maximum tolerable limits for aflatoxin B1 alone in various types of feed.
In Italy, since 2016 the Official National Control Plan for Mycotoxins with the aim of providing indications to the regional authorities and autonomous provinces on the official control of the contaminant mycotoxins, and therefore on aflatoxins, in food productsContamination prevention measures
Contamination prevention measures
Aflatoxins, as well as other mycotoxins, are highly heat-resistant (thermostable) substances, therefore the heat treatments commonly used in industrial processes and in common household preparations are not able to reduce the original level of these substances.
With regard specifically to aflatoxins, the guiding principle for containing contamination levels consists in "acting on the most vulnerable phases of the agri-food chain," from field to table ". While in developing countries the poor conservation of food ( temperature, humidity) is a very important risk factor, in industrialized countries, such as Italy, the “field” phase is especially decisive. In our scenarios, the production of aflatoxins can take place both in the fields and during the storage phases after harvest.
With regard to the preventive actions to be carried out, by way of example, those relating to the cultivation most at risk of contamination by aflatoxin B1: corn are reported. To reduce the risk, it is useful to harvest corn at a humidity level of no less than 22%. This condition is extremely important to avoid that, after harvesting, in conditions of humidity such as to favor the proliferation of the growth of fungal spores, the probable presence of aflatoxins increases in an uncontrolled way.
Another very important phase is undoubtedly that of drying the product after harvesting, both as regards the time that elapses from harvesting to drying, and for the difference in temperature and the amount of time that characterize the ways in which the In fact, very high temperature differences reached in a short time should be avoided since they could cause cracks and micro-cracks in the external surface of the corn, thus favoring the attack of fungal spores during storage.Bibliography
Neal GE et al. Metabolism and toxicity of aflatoxins M1 and B1 in human derived in vitro systems [Summary]. Toxicology and applied pharmacology. 1998; 151: 152-8
European Food Safety Authority (EFSA). Opinion of the scientific panel on contaminants in the food chain on a request from the Commission related to the potential increase of consumer health risk by a possible increase of the existing maximum levels for aflatoxins in almonds, hazelnuts and pistachios and derived products. The EFSA Journal. 2007; 446: 1-127Link Further information
Link Further information
European Food Safety Authority (EFSA). Aflatoxins in food
Higher Institute of Health (ISS). National reference laboratory for mycotoxins and plant toxins
Ministry of Health. Official national control plan for mycotoxins in food 2016-2018
International Agency for Research on Cancer (IARC). Aflatoxins. 1993 (IARC Monographs on the evaluation of carcinogenic risks to humans n.56 p.245-395)