In 1993, aflatoxin was classified as a Class 1 carcinogen by the World Health Organization (WHO) Cancer Research Institute, and it is a high substance. The harmfulness of aflatoxin is that it has a destructive effect on human and animal liver tissues, and can cause liver cancer or even death in severe cases.
Recently, the Guangzhou Administration for Industry and Commerce announced the results of the second inspection of dairy products on the market in the second quarter. Well-known brands of Bright Butter, Nanshan Milk Powder, and Shawan Ginger Milk are all unqualified. 5 batches of Nanshan Beihui infant milk powder were found to be unqualified in the standard value for the content of aflatoxin M1. What is aflatoxin? What diseases can aflatoxins cause?
Aflatoxins are a group of products with similar chemical structures that are metabolized by Aspergillus flavus and Aspergillus parasiticus in food and feed. Aspergillus fumigatus can also produce aflatoxins, but the yield is low. There are 17 kinds of aspergillus, mainly including aflatoxins B1, B2, G1, G2, and metabolites M1, M2 derived from hydroxylation of B1 and B2 in vivo. The basic structure of aflatoxin is difuran ring and coumarin. Aflatoxin B1 is a derivative of dihydrofuran oxaphthalene, which contains a difuran ring and an Oxacillian (coumarin). The difuran ring is basic toxicity in structure, the Oxacillian is related to carcinogenicity. The toxicity of B1 (the toxicity of it is higher than that of potassium cyanide) and it’s carcinogenicity is extremely strong with heat-resistant (the decomposition temperature of B1 is about 268 °C, and the method of cooking is rarely destroyed). Aflatoxin B1 is the most common toxin in naturally polluted foods.
Distribution of Aflatoxin
Aflatoxins are mainly found in moldy foods such as peanuts, grains, nuts, and rice. The solubility of Aflatoxins in water ranges from 10 mg/L to 20 mg/L, and aflatoxins can be dissolved in large quantities in medium-polar organic solvent included chloroform, methanol, dimethyl sulfoxide, etc. It is insoluble in hexane, petroleum ether, and ether, but easily destroyed by alkali or strong oxidant. It is mainly absorbed by the digestive tract. After entering the human body, mostly of aflatoxin is distributed in the liver, kidney, and a small part in the blood, muscle. In adipose tissue, it’s metabolic processes in the body are mainly hydroxylation, demethylation, and epoxidation.
Why does the milk powder contain aflatoxin?
The main source of human exposure to aflatoxin in contaminated food. Two types of contaminated food can be ingested through the diet. The pathway 1 is that people ingested plant food contaminated with aflatoxin (mainly B1), and the pathway 2 is that people take food polluted from the feed with Aflatoxin (mainly M1), including milk or dairy products (including cheese, milk powder, etc.). He Jianguo (microblogging), deputy professor of the Department of Nutrition and Food Safety, College of Food Science, China Agricultural University, said that aflatoxin is highly toxic and carcinogenic. Aflatoxins are produced by microorganisms, unlike melamine which is a malicious addition. Aflatoxin is fat-soluble and if the aflatoxin is present in the feed of cattle, the content of aflatoxin in beef will not be high. But in the internal organs, especially the liver, it will be high in the content of aflatoxin. Aflatoxin is very heat-resistant and will not be destroyed. When heated to 280°, Aflatoxin will not be removed. As long as it is contained in the milk powder, it will not be removed. And Ultraviolet rays can only destroy in small amounts.
The physicochemical characteristic of aflatoxin
1. Aflatoxin is extremely toxic
The toxicity of Aflatoxins is much higher than that of cyanide, arsenide and organic pesticides, among which B1 is the most toxic. When a person consumes a large amount, it may occur acute poisoning, acute hepatitis, hemorrhagic necrosis, hepatic steatosis, and bile duct hyperplasia. When the aflatoxin is continuously taken in a small amount, it can cause chronic poisoning, growth disorders, and cause fibrous lesions that result in fibrous tissue hyperplasia. The carcinogenicity of aflatoxin is also the first, and it is one of the most known carcinogens.
2, Aflatoxin has heat resistance
In general, the cooking temperature cannot destroy aflatoxin, and the cracking temperature is 280 °C. It is low solubility in water, soluble in oil and some organic solvents such as chloroform and methanol, but insoluble in ether, petroleum ether, and ethane.
Its toxicity is currently considered to have three clinical features included acute poisoning, chronic poisoning, and carcinogenicity:
(1) Acute poisoning
It is a highly toxic substance, which is 10 times more toxic than cyanide, 68 times more than arsenic, and only secondary to botulinum toxin that is the most toxic among the known molds. It’s toxic effects for any animal, is the liver the main change, which is acute hepatitis, hemorrhagic necrosis, hepatic steatosis, and bile duct hyperplasia. There are also mild lesions in the spleen and pancreas.
(2) Chronic poisoning
Long-term intake in small doses of aflatoxin can cause chronic poisoning. The main change is characterized by damage to the chronic liver, such as hepatic parenchymal cell degeneration and cirrhosis, slow growth, weight loss, infertility or low birth weight.
Aflatoxin is the most carcinogenic chemical known currently, and its carcinogenic characteristics have a wide range and can induce experimental tumors in fish, poultry, various experimental animals, livestock and primates. The carcinogenic strength is large, and its carcinogenic ability is great. It can induce a variety of cancer, and also can appear teratogenic, mainly inducing cancer in the liver, gastric, kidney, lacrimal adenocarcinoma, rectal, breast, ovarian, small intestine, other parts of the tumor.
What is the harm of aflatoxin ?
1. Aflatoxin is a very toxic substance. The harmfulness of aflatoxin is that it has a destructive effect on human and anima’s liver tissues, and it can cause liver cancer or even death in severe cases. In naturally contaminated foods, aflatoxin B1 is the most common, and it’s toxicity and carcinogenicity are also the strongest. If the enterprises of production use inferior raw materials, such as moldy peanuts, rapeseed, corn, etc. to produce edible oil, it may cause excessive aflatoxin by the standard and will pose a threat to the health of consumers.
2. Suppress immune function. AF that binds to DNA and RNA, can affect protein synthesis and inhibit immune function. Aflatoxin B1 (AFB1) acts on causing lymphoid tissues and thymic atrophy and dysplasia, delayed activation of lymphokines, and reduced lymphocyte production. AF can reduce the resistance of piglets to disease. And the toxicity of pigs depends on the intake amount of aflatoxin. In the long-term intake of a small amount of AF, there will be no obvious symptoms of poisoning, but it can reduce the immune function and disease of pigs Resistance that causes secondary infectious diseases and affects their production and reproductive performance.
3. Damaged tissues and organs of livestock and poultry. AF is a highly toxic hepatic toxin that causes liver damage in animals and causes serious damage to the kidneys and other tissues and organs. After porcine poisoning, it will occur hepatic lobule, coagulative necrosis, hemorrhage of hepatocytes around the central vein, significant nodular hyperplasia of the liver, gallbladder edema, submucosal muscle layer, subserosal effusion, and finally died of severe liver hemorrhage. After poultry poisoning, their liver is atrophied or swollen. After bovine poisoning, it will occur liver damage, edema, diarrhea, keratoconjunctivitis, etc. Acute poisoning can occur in the ingestion of foods contaminated with aflatoxin. The clinical manifestations are mainly jaundice with symptoms such as vomiting, anorexia, and fever. In severe cases, it will appear ascites, lower extremity edema, and even death in 2 to 3 weeks later with gastrointestinal bleeding.
4. Reduce the productivity of livestock and poultry. AF is a highly toxic and highly mutagenic compound. The content of nutrients in the diet contaminated by mold is reduced. The contaminated diet is with the emitted musty smell, deteriorated the sensory properties of the feed, and the poor palatability. Feeding mildewed feed can lead to poultry poisoning, it will occur reduced feed intake, slow growth, decreased daily weight, lower rate of conversion in gain and feed, a significantly lower rate of birth, relatively higher number of weak piglets and deaths of piglets, digestive disorders, loss of appetite, malnutrition, anemia, slowing weight gain and stagnant growth and development.
5. Damage to the reproductive system of livestock and poultry. AF can occur cause many diseases in sow, including abortion, weak and stillbirths, reducing the number of litters and the survival rate of piglets, ovarian malformations, uterine dilatation, swelling, ovarian atrophy, prolong estrous cycle, fecundity decline and animal testicular atrophy in male.
6. It is carcinogenic, mutagenic, teratogenic. AF has carcinogenic, mutagenic and teratogenic effects, and its toxicity is 68 times that of arsenic and 10 times that of potassium cyanide. Long-term ingestion of feed containing AF can cause liver cancer in animals. AF exposure was consistent with the P53 gene mutation. AFB1 detoxification enzyme mutation, AFB1 adduct, and P53 gene mutation were associated with liver cancer.
7. Aflatoxin is highly harmful and has a wide range. To prevent the occurrence of aflatoxin poisoning and maintain human health, more than 70 countries and regions in the world have imposed a limit on the content of aflatoxin in food. The following are the inspection and quarantine requirements for aflatoxins in foods in some countries and regions. The allowable amount of aflatoxin B1 in foods in China (GB2761-81) stipulates that corn, peanut kernels, and peanut oil should not exceed 20 μg/kg, corn and peanut kernel products (converted according to raw materials) should not exceed 20 μg/kg, rice and other edible oils shall not exceed 10 μg/kg, and other foods, beans, and fermented foods shall not exceed 5 μg/kg. They shall not be detected in infant milk, a variety of substitute foods. Other foods may be implemented according to the above standards. The aflatoxin M1 limited standard (GB9676-88) stipulates that it should not exceed 0.5 μg/kg in milk and milk products.