Mycotoxicosis and food mycotoxins

Overview

The mycotoxicosis is food poisoning caused by ingestion of food containing a sufficient quantity of mycotoxins. These are toxic metabolites produced by certain molds, which may be contained in the spore, the thallus or excreted in the substrate on which the mold has grown.

It distinguishes mycotoxicoses following acute ingestion, at once or several times closely, a relatively large dose of mycotoxins, and mycotoxicoses following chronic ingestion of low volumes but repeated.

Various cases of poisoning by molds are known for a long time. These include the ergotism known since the Middle Ages, angina septic (or ATA "Alimentary Toxic Aleukia") and acute cardiac beriberi (or " yellow rice disease ") known since the Second World War. But it is mostly from 1960, when more than 100 000 turkeys died in England following the consumption of animal feed contaminated with mycotoxins produced by Aspergillus flavus that research on these metabolites has increased significantly.

Now we know more than 150 species of toxigenic molds. However, the detection of food deemed a mold toxin does not necessarily mean the presence of mycotoxins. It depends on the strain, some strains produce mycotoxins and others do produce no or little, of the substrate and environmental conditions (Table 2). It is then necessary to investigate and determine the mycotoxins in the food before it is declared unfit for human consumption.

Biological activity of mycotoxins

Mycotoxins have variable effects on humans, animals, plants and microorganisms.

In humans, aflatoxin B1 is composed Hepatobiliary the most powerful carcinogen known. In addition, it has a teratogenic effect (affects the developing fetus). Both effects can be cumulative.

In animals, mycotoxins are responsible for tissue bleeding, anorexia and hepatitis. These symptoms can lead to death. The organs affected are the liver, but also the spleen, pancreas and kidneys.

In plants, mycotoxins inhibit seed germination and synthesis of chlorophyll.

On regard to the effect of mycotoxins on microorganisms, several bacterial genera (Bacillus, Flavobacterium, etc..) And some yeasts are inhibited by aflatoxins. Some mycotoxins have been used as antibiotics, but because of their toxic effect they were abandoned for this use. This is the case with the patulin and citrinin.

Major mycotoxins

There are several types of mycotoxins that have variable effects on human health. These toxins are classified into different groups according to their chemical structure. The main groups are: Aflatoxins, Patulin, Ochratoxin, citrinin, Citréoviridines, Trichothecenes and Zearalenone. Note that a mycotoxin can be produced by several species of fungi, and mold may develop several groups of mycotoxins.

In this document we will focus mainly to aflatoxins, patulin, ochratoxin and citrinin.

Aflatoxins

Aflatoxins are the most well-known mycotoxins. They are produced mainly by Aspergillus flavus, but also by other species of fungi such as Aspergillus parasiticus and Aspergillus nomius. These micro-organisms are present on many substrates, but particularly on oilseeds and their cakes.

After the death of several turkeys in England in 1960, it was established the relationship between the disease and the consumption of a peanut meal from Brazil, invaded by Aspergillus flavus.

Aflatoxins are a group of 18 structurally related compounds. The most common are the aflatoxins B1, B2, M1, G1 and G2. Aflatoxin B1 (Figure 2), the most important causes of acute intoxication in hepatic parenchymal necrosis and hemorrhage, disorders associated with chronic intoxication are of a different order. There is a proliferation of epithelial cells of the bile duct, liver degeneration, there is cirrhosis, which develops into steatosis, bile duct proliferation, fibrosis, adenoma and carcinoma. Aflatoxin B1 is currently considered the most important carcinogenic agent of natural origin known.

Patulin

Patulin (Figure 3) is a chemical produced by a number of molds such as Penicillium expansum and Aspergillus clavatus.

Although apples and derivatives appear to be the main source of patulin, any moldy or rotten fruit may contain this toxin. In animal feed, a mycotoxin that is fairly common in wet silage and cereals grown in Germoir.

The carcinogenicity of patulin is not yet proven. However, we know it has neurotoxic and immunotoxic effects in animals. The fear that it does not cause similar effects in humans resulting in a desire to limit as much as possible exposure to this toxin. JECFA (Joint Expert Committee on Food Additives of FAO / WHO) has evaluated the effect of patulin, and has set a tolerable daily intake provisional maximum 0.4 g / kg bw .

Citrinin

The Citrinin (Figure 4) is a mycotoxin first isolated from Penicillium citrinum, common particularly on rice and barley moldy. It is also produced by other species of Penicillium and of Aspergillus.

Citrinin the cause of kidney disorders, it causes a considerable enlargement of tubular collectors, it acts by destruction of tubular epithelium. Urinary excretion is two and a half times greater than normal.

Ochratoxin

The ochratoxins is a group of mycotoxins produced mainly by Aspergillus ochraceus and Penicillium viridicatum. They are mainly found in cereals (wheat, corn, rye, barley), but also in meat and offal from animals fed with contaminated food, as well as in coffee, cocoa, beans and dried fruits.

There are 3 ochratoxins which differ slightly from each other in their chemical structure (Figure 5): Ochratoxin A, ochratoxin B and ochratoxin C. However, these differences have profound effects on their potential toxic. Ochratoxin A (OTA) is the most widespread and is considered the most toxic of the group.

The acute and chronic toxicity of OTA are linked directly or indirectly to its property to inhibit protein synthesis by competition with phenylalanine in the reaction catalyzed by phenylalanyl-tRNA synthetase. The cytotoxic effects of ochratoxin are also partly related to oxidative processes, mobilization of intracellular calcium, the inhibition of mitochondrial respiration and inhibition of ATP synthesis. Because of the difficulty to correlate the potential effects of OTA with its presence in human blood, all experimentally observed effects in animals have not yet been demonstrated in humans. But the most toxic effects are feared nephrotoxicity, teratogenicity and carcinogenesis.

Preventive measures

Mycotoxins are affected differently by the treatment technology. They are relatively heat stable and only 24 to 40% may be destroyed by heat treatment. Similarly, the freezing does not usually their inactivation. This is the ionizing radiation is the most effective treatment, although it does not eliminate all, unless you are using levels of very high ionization .

Preventing mycotoxicoses necessarily pass through the prevention of mold growth in food, and this by:

• The control of storage conditions and distribution of post-harvest, particularly in avoiding infestation of cereals and other oilseeds, drying quickly yields an artificial or natural and storing products in well ventilated areas and low relative humidity .
• The addition of antimicrobial agents that inhibit the growth and metabolism of fungi (sulfites, bisulfite, benzoic acid, etc.).
• Effective disinfection of the warehouses, chain packing, equipment and utensils.
• And in general, in accordance with good hygiene practices at all levels of the food chain.