As food contains rich protein, fat and essential amino acids for human body, a certain amount of N-nitroso compounds will be produced in these nutrients after processing such as pickling, baking, frying and frying;In addition, some nutrients in food may self synthesize N nitroso compounds in the human gastric juice environment, thus causing harm to human body.Therefore, the sources of N-nitroso compounds in food include production during processing and endogenous self synthesis.[1]
The general formula of molecular structure of N-nitroso compounds R1 (R2)=N-N=Ondma andN-nitrosamideR1 and R2 of N-nitrosamine arealkylorAryl group；R1 of N-nitrosamide is alkyl or aryl, R2 is amide, includingaminoFormyl group, acetyl and nitro groups;Both can have heterocyclic compounds.The production and application of N-nitroso compounds are few, but the precursorsNitriteAnd secondary amines and amides widely exist in the environment and can form N-nitroso compounds in vitro or in vivo.In the urban atmosphereWater bodyMany N-nitroso compounds are found in soil, fish, meat, vegetables, cereals and tobacco.Most of them are liquids and solids, which enter the body mainly through the digestive tract.It is highly toxic, and its oral LD50 for experimental animals is 150-500mg/kg (body weight).Acute toxicity: N-nitrosamine mainly causes central hemorrhage and necrosis of hepatic lobule, and can also cause pulmonary hemorrhage and bloody exudation of thoracic cavity and abdominal cavity, which is irritating to eyes, skin and respiratory tract;The direct stimulation of N-nitrosamine is strong, and the damage to the liver is small, causing peripheral damage to the liver lobule.It has been found that about 200 kinds of N-nitroso compounds are carcinogenic to mice, rats, guinea pigs, rabbits, dogs, pigs, monkeys and fish, among which rodents are the most sensitive.The methods of poisoning include inhalation, tracheal injection, oral, subcutaneous injection and intravenous injection, and also mixing nitrite and amine with feed and drinking water to feed animals.The oral daily dose of 1mg/kg (body weight) or less can cause cancer. If a large dose is given once, it can cause cancer 9-12 months later, and it is found that transplacentalCarcinogenesis。See the attached table for target organs of some N-nitroso compounds causing cancer.Nitrosamines are indirect carcinogens, nitrosamines are direct carcinogens, and the ultimate carcinogens may be onium ions and azoalkane。N-nitroso carcinogenic compoundsMutagenicity testThere are positive results, teratogenicity and embryotoxicity.Epidemiological investigation has found that the intake of N-nitroso compounds is related to the occurrence of human gastric cancer and esophageal cancer, but the evidence is still insufficient.
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Nitrate and nitrite are the most common nitrosates.Nitrite and nitrate exist widely in the natural environment.When plants synthesize necessary plant proteins during their growth, they need to absorb nitrate as their nutrient;Nitrate absorbed by vegetables is reduced to nitrogen by plant enzymes, and forms amino acids and nucleic acids with organic acids synthesized through photosynthesis.When photosynthesis is not sufficient, plants will accumulate excess nitrate.Nitrite and nitrate can also enter food through artificial addition, for example, they can be used as preservatives and color fixatives to preserve meat, fish and cheese.As early as the early 20th century, people found that adding nitrite was the reason for the change of color and flavor of cured meat, and it could inhibit the growth of some putrefactive bacteria and pathogenic bacteria to achieve the purpose of antisepsis and coloring.[1]
Toxicity and hazard
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The toxicity of different types of nitroso compounds varies greatly. Most nitroso compounds are low toxic and
It is moderately toxic, and some are highly toxic or even highly toxic.Different compounds have different toxic mechanisms, including liver injury, kidney injury, vascular injury, etc.
carcinogenicity
Many animal experiments have proved that N-nitroso compounds have carcinogenic effects.N-nitrosamines are relatively stable and need to be metabolized into active substances in the body to have carcinogenicity, also known as pre carcinogens.N-nitrosamines are unstable and can be directly degraded into diazo compounds at the site of action, and combine with DNA to play a direct role in carcinogenesis and mutagenesis. Therefore, N-nitrosamines are also called terminal carcinogens.Up to now, no animal has been found to be resistant to the carcinogenic effect of N-nitroso compounds. In addition, multiple drug administration routes can cause tumorigenesis in experimental animals, whether inhaled through the respiratory tract, ingested through the digestive tract, subcutaneous, intramuscular injection, or skin contact can induce tumorigenesis.Repeated exposure or a large dose of medicine can induce tumor, and there is a dose effect relationship.In animal experiments, the evidence of carcinogenic effect of N-nitroso compounds is sufficient.In terms of human epidemiology.Epidemiological data in some countries and regions show that some human pain may be related to it. For example, the high incidence of gastric cancer in Chile may be related to the use of nitrate fertilizer, which leads to the high content of nitrate and nitrite in the soil;Japanese like salty food
Fish and pickled vegetables have a high incidence of gastric cancer. The former has a high content of amines, especially secondary and tertiary amines, while the latter has more nitrites and nitrates.[2]
2. Teratogenicity and mutagenicity
In the study of genotoxicity, it is found that many N_nitroso compounds can induce gene mutation, chromosome abnormalities and DNA repair disorders through body metabolism or direct action.N-nitrosamine can cause malformations of brain, eyes, ribs and spine in offspring rats, but the teratogenic effect of N-nitrosamine is very weak.Dimethylnitrosamine has mutagenicity and is often used as a positive control for mutagenicity tests.[1]
Prevention and control measures
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To prevent the harm of N_nitroso compounds to human health, we can start from many aspects.According to the source of the N-nitroso compounds in the aforementioned food, the nitrite and nitrate in the food can be controlled from the source, or the N_nitroso compounds produced in the food processing can be reduced or reduced by blocking.In addition, it is also a reasonable way to effectively control the production of N nitroso compounds in food by formulating standards and specifications for the limit of N nitroso compounds in food, strictly controlling industrial emissions, scientific fertilization and other measures.
(1) Apply fertilizer scientifically and rationally.When no or less ammonium nitrate and other nitrate nitrogen fertilizers are applied during vegetable planting
Using molybdenum fertilizer, organic fertilizer, microbial fertilizer, humic acid fertilizer, etc., screening low accumulation nitrite nitrogen fertilizer suitable for vegetable application can also effectively reduce the nitrate content in vegetables [1183; in addition, nitrogen fertilizer combined with phosphorus and potassium fertilizer can promote the synthesis of protein and important nitrogen compounds, reduce the accumulation of nitrate, control and reduce the nitrite content in vegetables.
(2) Block the synthesis of N-nitrosamines in food.Use and find some blockers to prevent natural food
The synthesis of nitrosamines is reduced by the reaction of middle amines with nitrite.For example, the addition of vitamin C, vitamin E, phenols, gallic acid and some reducing substances during food processing has the effect of inhibiting and reducing the synthesis of nitrosamines, and has no effect on the coloration and antibacterial effect of nitrite.At present, many countries in the world advocate the addition of vitamin C in the processing of meat products.In the United States, when 120 mg/kg sodium nitrite is added, 50 mg/kg vitamin C is added to reduce nitrite to NO and promote the production of nitroso myoglobin, which not only increases the coloring effect, but also reduces the production of nitrosamines in meat products.
(3) Improve food processing methods.The synthesis of nitrosamines can be eliminated or reduced by using the cold smoke of sawdust produced by smoke liquid or smoke generator instead of burning wood to smoke smoked products.When curing meat and fish products, the ingredients such as salt, pepper and chili powder should be packaged separately, and should not be mixed together to produce nitrosamines.At the same time, nitrate and nitrite should be used as little as possible in the processing of meat products.
(4) Improve and enhance the way of eating.Nitrate and nitrite in food cannot be eliminated completely at present
It is necessary to reduce the harm of nitrite to human body and cultivate scientific food consumption and eating habits. ①Do not eat mildewed and overnight cabbages.Try to buy fresh vegetables.From the perspective of nutrition, fresh vegetables have less loss of nutrients;From the perspective of safety, the nitrite content of fresh vegetables is low.In addition, vegetables should be arranged, washed, cut, fried and eaten immediately when cooking. ②Do not eat fermented pickles.The nitrite content of pickled pickles rises to the highest level after 6 days, and then gradually decreases. After 20 days, it is basically completely decomposed. Therefore, it is better to pickle pickles for 1 month before eating.In pickling, 400 mg vitamin C can be added per kilogram of pickle to prevent nitrite from forming nitrosamines. ③When processing pickles, use artificial fermentation instead of natural fermentation.Compared with natural fermentation, artificial inoculation of fermented pickles can accelerate the fermentation rate and shorten the fermentation time.A large amount of lactic acid can inhibit the infection of mixed bacteria, increase the yield of pickles, improve the flavor of pickles, and improve the quality of pickle bacteria [119]. ④Soak vegetables before cooking.Nitrite is soluble in water. Vegetables, especially sauerkraut, should be washed and soaked before cooking.With the increase of water change times and soaking time, the nitrite content in sauerkraut significantly decreased [120 |.⑤ Do not drink 6 kinds of water containing a large amount of nitrite: warm, lukewarm water that has been burned on the stove all night or placed for 1 to 2 days, boiled water that is re boiled overnight in an automatic water heater or residual boiled water that has been repeatedly boiled, water that is not the same day in a thermos bottle, water from a steamer that has steamed bread, rice, meat and other food, and bitter well water.The content of nitrite in the above six kinds of water is relatively high, so it is not suitable for drinking.
(5) Formulate corresponding standards and regulations.The food hygiene supervision department should start from the source and strictly monitor the use of nitrate and nitrite by enterprises.The GB 2760-2011 National Standard for Food Safety Hygienic Standard for the Use of Food Additives issued by China clearly stipulates the use of nitrate and nitrite for different food types, and stipulates their maximum use limits.[1]
