Aflatoxine

Discovered in 1960 in England, the aflatoxine is a Mycotoxine produced by Champignon S proliferating on seeds preserved in hot and wet atmosphere. It is harmful as well at the man as in the animal, and has a capacity high Cancérigène.

Production of aflatoxines

Aflatoxines sets up a group of 18 made up structurally close (an assembly of a coumarin and 3 furans). They are produced by Aspergillus flavus (which produces also aflatrem, acid cyclopiazonic, acid aspergillic), Aspergillus parasiticus and Aspergillus nomius . These micro-organisms ubiquitaires have few requirements of growth: a temperature ranging between 6 and 50°C, a source of carbon and nitrogen and an activity of water higher than 80%. However under certain conditions (temperature ranging between 13 and 45°, important moisture, presence of certain fatty-acids), they can produce secondary metabolites: aflatoxines, which is thus Mycotoxine S. Among most current, one finds the AFB1, the AFB2, the AFM1, the AFG1 and the AFG2.

General effects of aflatoxines

Very many food products intended for the man or the animals can contain aflatoxines in sometimes large quantity: seeds of groundnuts, corn (in grain, Ensilage,…), corn, various cereals, almonds hazel nuts, nut, pistachios, figs dates, cocoa, coffee, manioc, soya…. Aflatoxines B1 and B2 (AFB1 and AFB2) is most usually met in food. Metabolized by various enzymes microsomiales aflatoxines is eliminated in form glycurono and sulfo combined by urinary tract, the Lait or the bile. At the time of the metabolisation of aflatoxines, some derived highly reactive epoxies can appear. Strongly électrophiles they react with the nucleophilic groupings of the DNA by intercalating between the bases or of proteins. Aflatoxines has also a strong effect Tératogène and can with high amounts result in death in a few hours at a few days according to the amount and the sensitivity of the animal. They in addition have a role on phosphorylations and the lipogenesis, as well as immunosuppressive properties. Lastly, aflatoxines is recognized as being the most powerful natural carcinogens. The acute intoxication by aflatoxines results in death in general with sometimes symptoms of depression, anorexia, diarrhea, Ictère or weakens. The primarily hepatic lesions (necrose, Cirrhose) evolve/move in the long run in Hépatome or Carcinome. The chronic forms of aflatoxicose result in a fall of the performances for the livestock, an anemia, a light ictère and a cancerous evolution in the long term. The presence of mycotoxins in food poses large problems of public health and animal health. The AFB1 is regarded as most toxic of aflatoxines.

Aflatoxines in milk

In the cattle, aflatoxine B1 absorptive with contaminated food is metabolized on the level of the liver in a derivative 4-hydroxy - called aflatoxine M1 - which in the dairy animals (in particular cows, ewe and goats) is excreted in the Lait. There exists moreover one linear relation between the concentration of excreted AFM1 and the quantity of introduced AFB1. Thus, it was shown, in the milch cow, that 0.5 to 4% of aflatoxine B1 introduced are found in the form of aflatoxine M1 in milk. This mycotoxin preserves - with a less degree certainly - the important carcinogenic properties of aflatoxine B1. Also, the cumulative effect related to regular and iterative ingestion such toxins makes run great risks to the children and the large infants consuming milks and dairy products. This risk is all the more important as aflatoxine M1 resists the usual treatments of conservation and transformation of the dairy products (heat, cold, freeze-drying…). One finds almost the totality of aflatoxine M1 in skimmed milk, and the products obtained by lactic precipitation (yoghourts, soft white cheeses, lacteous creams…), whereas very little in butter of it is found. This is related to the presence of hydrophobic interactions between aflatoxine M1 and the Caséine S, and in fact it is frequent to note an enrichment of the initially contaminated Fromage S in aflatoxine M1 during draining (the AFM1 bind to proteins of milk and thus are concentrated in curd than in fresh milk and small milk). Currently, the maximum rate of AFM1 authorized in milk is of 50ng/kg. To limit the concentration of aflatoxines in milk, various measurements can be taken upstream production of food intended for the dairy animals:

an enough long system of rotation of crops to allow the cleansing of the cultures;
a use of varieties of corn less sensitive to the fungic contamination or earlier;
a system of harvest which avoids breaking the grains;
an analysis of the ensilage used for the food of the animals (detection and/or quantification of the AFB1 in samples of ensilage), and in the event of detection of aflatoxines, a shrinking of the silo of the parts presenting of the signs of aerobic deterioration and a treatment of the remaining ensilage to propionate, food additive accelerating fermentation. Other chemical agents such as the acids, the bases (ammonia, soda), of the oxidising agents (hydrogen peroxide, ozone), of the reducing agents (bisulfites), of the chlorinated agents, formaldehyde can also be used to degrade or biotransformer aflatoxines. One also can épandre a hydrodispersible agent of ensilage containing a lactic stock of patented bacterium: Lactobacillus buchneri NCIMB 40788, recognized for its capacity to improve the aerobic stability (antifongic action) of the ensilages with strong dry matter. This agent is particularly recommended for the corn ensilages open to spring/be;
a constant cover of the ensilage;
In the case of corn grains, a drying of the grains before the warehouse and a maintenance of the level of moisture to 14 or 15%;
a ventilation in the desiccator with fodder.

A regular analysis of milk and dairy products (detection and/or quantification of the AFM1 starting from samples of fresh milk, dried milk reconstituted or cheese) also make it possible to limit the risks of intoxication.

See too

mycotoxins in the food
Detailed Pure information one mycotoxins
Aflatoxin standards

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