Toxicity of aflatoxins

作者：admin  点击次数：21  发布时间：2025-04-03

AFT has strong acute toxicity, as well as obvious chronic toxicity and carcinogenicity.
(1) Acute toxicity AFT is a highly toxic substance that is extremely toxic to fish, chickens, ducks, rodents, rabbits, cats, pigs, cattle, monkeys and humans. Ducklings and young fresh fish are most sensitive to AFB, followed by rodents and other animals. Most sensitive animals die within 3 days after ingesting a certain amount of toxin. Postmortem examinations revealed that their livers were significantly damaged, with acute lesions such as liver parenchymal necrosis, bile duct epithelial hyperplasia, hepatic fatty infiltration and hepatic hemorrhage. In addition, in vitro tests have also found that a concentration of 1 mg/L of aflatoxin B can prevent DNA and RNA synthesis in human liver cells. AFT can also cause acute poisoning in humans. The most typical example is the outbreak of aflatoxin hepatitis in 200 villages in two states in India in 1974. Nearly 400 people were poisoned in this poisoning, with symptoms such as fever, vomiting, anorexia, jaundice, ascites, edema and even death. In the autopsy, hepatobiliary hyperplasia was found. The villagers were poisoned by eating moldy corn. The test found that the content of aflatoxin B in the moldy corn was 6.25~15.6mg/kg. It is estimated that the average daily intake of aflatoxin B per person is 2~6mg. (2) Chronic toxicity If AFT is taken in for a long time at a small dose, it will also produce chronic toxicity, which is mainly manifested as animal growth disorders and subacute or chronic liver damage. Other symptoms include weight loss, slow growth and development, decreased food utilization, infertility or reduced litter size in female animals. In addition, aflatoxin can also increase the activity of alkaline phosphatase, transaminase and citric acid dehydrogenase, increase the fat content in the liver, reduce liver glycogen, reduce the amount of plasma albumin, reduce the A/G ratio and reduce the vitamin A content in the liver. (3) Carcinogenicity AFT is the strongest chemical carcinogen discovered so far. Its liver cancer-inducing strength is 75 times greater than that of dimethylnitrosamine.
In addition to long-term chronic effects that can induce tumors, there is also a "shock dose" that can cause cancer. Some people gave rats a dose of 7 mg/kg body weight of AFB, a total of 15 female rats, and 7 of them developed liver cancer at 26 months. AFT can not only induce liver cancer, but also induce tumors in other parts of the body, such as gastric adenocarcinoma, kidney cancer, rectal cancer, and tumors in the breast, ovary, and small intestine. Aflatoxin B, administered intratracheally, can induce tracheal squamous cell carcinoma. 5. Preventive measures
The main measure to prevent AFT from endangering human health is to prevent food from being contaminated by aflatoxin and its toxins, and to minimize the possibility of AFT being ingested into the human body along with food. The specific measures are as follows: (1) Food mold prevention This is the most fundamental measure to prevent food from being contaminated by AFT. Good agricultural production technology should be used to prevent mold from the field. First of all, we must prevent insects and lodging. When harvesting, we must promptly remove moldy corn cobs, and the corn after threshing must be dried in time. The moisture content of grains must be controlled below 13%. Usually, the moisture content of corn is below 12.5%, and the moisture content of peanut kernels is below 8%. This makes it difficult for mold to reproduce. Attention should be paid to low-temperature storage. For example, underground storage is more effective. In addition, attention should be paid to ventilation during storage. Some people have tried to use inert gas instead of air or nitrogen filling to prevent mold, and the effect is acceptable. Some areas have tried to use various mold inhibitors to preserve grains, but attention should be paid to their residues in food and their own toxicity.
The selection and cultivation of new varieties of grains and beans that are resistant to mold will be an important aspect of future mold prevention work. (2) Removal of toxins mainly involves the removal of toxins by physical, chemical or biological methods, or the use of various methods to destroy toxins. The specific methods are as follows:
① Selection of moldy grains: This method has a good effect in family or small-scale production. It mainly removes grains that are bad, damaged, wrinkled, discolored, and worm-eaten.
② Rolling processing method: This method is mainly suitable for contaminated rice. The toxin content in rice bran is high, so rolling processing can reduce the toxin content in rice grains, but the disadvantage is that there is a lot of nutrient loss and a large amount of grain loss.
③ Alkali detoxification of vegetable oil: Alkali refining itself is a processing method for oil refining. Under alkaline conditions, the acetone ring in the structure of aflatoxin is destroyed to form coumarin sodium salt, which is soluble in water. Therefore, adding alkali and then washing with water can remove the toxin.
④) Physical removal method: Vegetable oil containing toxins can be added with adsorbents such as activated white clay or activated carbon, and then stirred and placed. The toxins can be adsorbed to achieve the detoxification effect.
⑤ Water rubbing method: When washing rice, rub it with water, pour off the suspended matter with the water, and wash it repeatedly several times until the washing liquid is clear. Most of the toxins can be removed, but vitamin B is also lost a lot.
⑥ Microbial detoxification method: Some molds, bacteria, etc. can remove toxins, but the nutrients in food are also consumed. The actual application is not yet mature.
In addition, some people also use sunlight or ultraviolet radiation to destroy toxins, and brewing contaminated grains into distilled liquor can also remove toxins. Foreign countries also use organic solvents to extract toxins, use chemical drugs to destroy toxins, or use high temperatures to destroy toxins, all of which have achieved certain results.
(3) Formulating the maximum allowable amount of AFT in food to limit the content of aflatoxin in various foods is also an important measure to reduce the harm of toxins to the human body.
(III) Ochratoxin
Ochratoxin (ochratoxin) is a group of at least 7 structurally related mold metabolites produced by Aspergillus and Penicillium, including ochratoxin A, B, C and D. Among them, ochratoxin A (ochratoxinA, OTA), the structure is shown in Figure 2-2. Among all ochratoxins, OTA is the most toxic and can be produced by Aspergillus, Aspergillus niger, Penicillium viridiflorum, Penicillium arcus, Penicillium variegatum, etc. OTA is heat-resistant and cannot be destroyed under normal cooking conditions. It is slightly soluble in water and can produce a faint green fluorescence under ultraviolet light. The toxin is quite stable and can be stored in a refrigerator away from light for one year after being dissolved in ethanol.
1. Toxin production conditions and food contamination
OTA is produced in the largest amount at 30℃ and A=0.95, but the toxin production conditions of different strains are also different. Ochratoxin mainly contaminates corn, soybeans, cocoa beans, barley, lemon fruits, pickled ham, peanuts, coffee beans, etc. Ochratoxin can produce toxins in natural food matrices, synthetic or semi-synthetic culture media. Cultivating the strong toxin-producing strain of Ochratoxin on crushed wheat grains can produce a large amount of OTA, while using a medium containing 4% sucrose can produce OTA.