Nitrite, which contains nitrite anion (NOtwo−）Salt.The most common is sodium nitrite, which is white to yellowish powder or granular, slightly salty, and easily soluble in water.
Nitrate and nitrite widely exist in human environment and are the most common nitrogenous compounds in nature[1]。Nitrate in human body can be reduced to the precursor of nitrite and N-nitroso compounds under the action of microorganisms.
Similar to salt in appearance and taste, it is widely used in industry and construction. It is also allowed to be used in meat products in limited quantities as a colouring agent.The probability of food poisoning caused by nitrite is high.
Eating 0.3-0.5g nitrite can cause poisoning, and 3g will cause death[2]。
On October 27, 2017, the list of carcinogens released by the International Agency for Research on Cancer of the World Health Organization (WHO) was preliminarily collated for reference. Nitrate or nitrite ingested under conditions leading to endogenous nitrosation was included in the list of Category 2A carcinogens.[3]
Nitrite poisoningIt refers to cured meat products with high nitrate or nitrite contentpickled cabbageIt can also be seen in drinking bitter well water containing nitrate or nitriteSteamer waterAfter that, nitrite can make low iron in the blood normally carrying oxygenhemoglobinOxidationMethemoglobinTherefore, the oxygen carrying capacity is lost and tissue hypoxia is caused.Nitrite isHighly toxicSubstance: adults can be poisoned if they ingest 0.2-0.5g, and can be killed if they ingest 3g.meanwhileEsophageal cancerIt is positively correlated with the amount of nitrite ingested by patients. The carcinogenic mechanism of nitrite is:gastric acidNitrite in food under equal environmentSecondary amine、Tertiary amineandamideEqual reaction produces strong carcinogenNitrosamine。Nitrosamines can also penetrateplacentaIt enters the fetus and has teratogenic effect on the fetus.
Infants less than 6 months old are particularly sensitive to nitrite, and clinically suffer from“Methemoglobinemia”Thirty five percent of the infants were caused by eating foods with high concentrations of nitrite or nitrate, and the symptoms were hypoxia, cyanosis, or even death. Therefore, the EU stipulated that nitrite should not be used in infant food.The onset of nitrite poisoning is rapid, with a general incubation period of 1-3 hours. The main characteristics of nitrite poisoning are cyanosis caused by tissue hypoxia, such as cyanosis of lips, tongue tips and fingertips, and cyanosis of eye conjunctiva, face and whole body skin in severe cases.Dizziness, headache, fatigue, rapid heartbeat, lethargy or irritability, dyspnea, nausea, vomitingabdominal pain, diarrhea, coma in severe casesconvulsions■ Incontinence in urine and stool may cause death due to respiratory failure.
Nitrite used in meat food as a preservative has always been considered asCarcinogenHowever, scientists from the National Institutes of Health found that this carcinogen can be used as a drug to treat sickle cell disease, heart disease and other diseases. This discovery is shocking.
For 100 years, scientists believe that nitrite has no benefits, but today, scientists have found its value.according toNBCIt was reported on September 5 that a nitrite relatedchemical compound——NO,markDr. T Gladwin and cardiologist Dr. Richard Cannon accidentally discovered the medicinal value of nitrite.Nitric oxide can dilate blood vessels, thereby increasing blood flow, but cannot be used as a drug.However, it is often used asFood preservativesHowever, nitrite has the same effect as nitric oxide and can be used as medicine, so the two scientists thought of nitrite.
Subsequently, the scientists conducted clinical trials.They injected a small amount of nitrite into healthy volunteers. As a result, the blood flow of volunteers tripled. When volunteers exercised, the nitrite content in their bodies immediately plummeted, indicating that their bodies were actively using nitrite.Therefore, scientists believe that nitrite can be used as a drug to treat sickle cell disease, heart disease, cerebral aneurysm and other diseases related to blood flow.
In this regard, Dr. Gladwin said in a play, "We treat human organs as hot dogs. Adding nitrite is equivalent to adding protective measures to protect the heart, lungs and brain from lack of oxygenoxygenAnd die. "
Related reports
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On August 15, 2012, Zhejiang Administration for Industry and Commerce released information on its website that during the spot check of food quality in the circulation field, it was found that the nitrite content of blood swallow products generally exceeded the standard, and the problem of blood swallow mainly came from Malaysia.The blood bird's nest, which often costs tens of thousands of yuan or two, is exposed to be made of dyeing, and some of the harmful substances of blood bird's nest nitrite exceed the standard by 350 times, even the weight is still supported by fish glue, pectin, and agar powder.
Since 2012, the bird's nest market has been vigorously rectified nationwide.On August 15, 2012, the Zhejiang Provincial Administration of Industry and Commerce released the results of the spot check on the blood swallow. Among the 30000 problematic blood swallows with a total of 200000 grams, the average nitrite content reached 4400 mg/kg, and the maximum was 11000 mg/kg.According to national mandatory standards《National Food Safety Standard for Use of Food Additives》It is stipulated that nitrite is only allowed to have trace residues in cured bacon and other products, with a limit of 30 mg/kg, and the maximum residue of smoked ham shall not exceed 70 mg/kg.For the nitrite that is added unintentionally and generated naturally, the National Standard for the Limits of Pollutants in Food stipulates that the limit is generally 3 mg - 5 mg/kg, and the limit for pickles is only 20 mg/kg.
"Many processing plants use chemical agents to remove hair, which saves most of the labor costs; and then by adding glue, water, sticking and other methods, 500 grams of raw materials can be produced into 750 grams of finished products." The above industry insiders said.It has been an open secret in the bird's nest industry to paint bird's nest with special colloids (super77, etc.) to achieve multiple purposes such as assisting in shaping, improving appearance, increasing weight, and concealing defects.
On June 12, 2012, the Ministry of Health and the State Food and Drug Administration jointly announced that in the future, restaurants such as hotels, food stalls and snack bars are prohibited from using nitrite as food additives.For this reason, people and experts who have been concerned about food safety applaud.
2. The decomposition of nitrate can produce nitrite and oxygen.
Basic use
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As a color fixative for meat products, nitrite can react with myoglobin in meat products to generate rose colored nitroso myoglobin, which can enhance the color of meat;It can also enhance the flavor of meat and the role of preservatives, prevent the growth of Clostridium botulinum and extend the shelf life of meat products[4]。
toxicity
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Toxicity Introduction
It is worth noting that high doses of nitrite will still produce large amountstoxicity。Eating nitrite by mistake may lead to nitrite food poisoning, and long-term use may even lead toEsophageal cancerandgastric cancer。Moreover, scientists lack clinical trials to prove that nitrite can treat heart disease and other diseases.Therefore, scientists are actively soliciting volunteers for clinical trials, and are beginning to find suitable drug manufacturers to be responsible for the research and development of nitrite drugs.
Nitrite is antiseptic and can beMyoglobinIt is more stable due to combination, so it is often added in the food processing industrysausageandBaconAs color retention agent to maintain good appearance;Secondly, it can prevent the production of Clostridium botulinum and improve the safety of meat products.However, if the human body absorbs too much nitrite, it will affect the operation of red blood cells, making the blood unable to deliver oxygen, and the lips and fingertips will turn blue, which is commonly known as "blue blood disease", and will seriously cause brain hypoxia or even death.Nitrite itself is not carcinogenic, but under cooking or other conditions, nitrite in meat can degrade with amino acids to produce strong carcinogenicNitrosamine。
Eating pickled meat products, pickles and spoiled vegetables with high nitrate or nitrite content can cause poisoning and death due to respiratory failure.[5]
Excessive nitrate intake can induce infantile methemoglobinosis. Because a large amount of nitrite in the human body combines with hemoglobin in the blood, the content of methemoglobin increases. Because methemoglobin cannot combine with oxygen, people suffer from hypoxia. The clinical manifestations are cyanosis of lips and nails, purpura of skin and other hypoxia symptoms, which can lead to death.It often occurs in areas with high nitrate content in drinking water, mostly in infants.
Infant congenital malformation
Nitrite can enter the fetus through the placenta, and infants within 6 months are particularly sensitive to nitrate, which has teratogenic effect on the fetus.
Goiter
Some studies believe that high nitrate intake can reduce the digestion and absorption of iodine by the human body, leading to goiter, but whether nitrate is the direct cause of goiter in the human body remains to be further verified.
cancer
When nitrous acid is used for coloring, nitrite reacts with amine in meat to generate nitroso compounds, or converts into nitroso amines under acidic environment in the intestine. These nitroso compounds are carcinogenic factors[4]。
Cause of poisoning
Causes of acute poisoning
The nitrite is mistaken for table salt, flour alkali, etc.
Adulterate.
Poisoning.
Eating vegetables containing a large amount of nitrite, especially fresh leafy vegetables.
Causes of chronic poisoning
Drink bitter well water and steam boiler water with high nitrate or nitrite content.
Eat pickled meat products, pickles and spoiled vegetables with high nitrate or nitrite content.
Poisoning mechanism
Nitrite isStrong oxidantAfter entering the human body, it can oxidize the low iron hemoglobin in the blood into methemoglobin, lose the function of oxygen transportation, and cause tissue hypoxia, cyanosis and poisoning.
Poisoning symptoms
1. Headache, dizziness, weakness, chest tightness, shortness of breath, palpitation, nausea, vomiting, abdominal pain, diarrhea and lipsnailSkin and mucous membrane of the whole bodyCyanosisEtc.
2. The skin and mucous membrane of the whole body present varying degrees of cyanosis（MethemoglobinemiaCyanosis caused).
3. Severe poisoning may cause coma, convulsion, respiratory paralysis, etc[1]。
test method
1. Take 3~5ml of the patient's venous blood, and the blood color is blue and purple.
2. Centrifuge precipitation, the plasma is pale yellow, indicating that the blue purple is caused by the abnormality of the cell itself.
3. Shake well and shake in oxygen or air for 15 minutes. If it returns to bright red, it indicates that the original blue purple is caused by the oxidation of methemoglobin.
4. Through the above simple tests, preliminary judgment can be basically made.
Determination of nitrite content in food
Principle: Under the condition of hydrochloric acid acidification, nitrite and p-aminobenzenesulfonic acid undergo diazotization reaction, and then combine with N-1-naphthylenedioic acid hydrochloride to form rose red dye.The nitrite content in food can be estimated by visual comparison between the sample after color reaction and the standard color developing solution of known concentration.
Operation:
1. Preparation of solution
4-aminobenzenesulfonic acid solution with mass concentration of 4mg/mL: weigh 0.4g of p-aminobenzenesulfonic acid, dissolve it in 100mL hydrochloric acid with mass fraction of 20%, and store it away from light.N-1-naphthylenediamine hydrochloride solution with mass concentration of 2mg/mL: weigh 0.2g N-1-naphthylenediamine hydrochloride, dissolve it in 100mL water, and store it away from light.Sodium nitrite solution with mass concentration of 5 μ g/mL: weigh 0.10g of sodium nitrite dried in a silica gel dryer for 24h, dissolve it with water and fix the volume to 500mL, then transfer 5mL of solution to a 200mL volumetric flask and fix the volume to 200mL.Extractant: weigh 50g of cadmium chloride and 50g of barium chloride, dissolve them in 1000mL of distilled water, and adjust the pH to 1 with concentrated hydrochloric acid.Aluminum hydroxide emulsion and sodium hydroxide solution with the concentration of 2.5 mol/L substance.
2. Preparation of standard color developing solution
Suck 0.20mL, 0.40mL, 0.60mL, 0.80mL, 1.00mL and 1.50mL sodium nitrite solution (equivalent to 1ug, 2 μ g, 3 μ g, 4 μ g, 5 μ g and 7.5 μ g sodium nitrite) with a graduated pipette, place them in 50mL colorimetric tubes respectively, and then take another colorimetric tube as a blank control.Add 2.0mL of p-aminobenzenesulfonic acid solution into each tube and mix well. After standing for 3~5min, add 1.0mL of N-1-naphthylethylenediamine hydrochloride solution into each tube and add distilled water to make the total volume in each colorimetric tube be 50mL. Mix well and observe the gradient change of sodium nitrite solution color.
3. Preparation of sample treatment solution (take pickles as an example here)
After marking the three jars of pickles, conduct the following treatment respectively.Weigh 0.4kg pickles, crush them with a juicer, and filter them to obtain about 200mL juice.Transfer 100mL of the solution to a 500mL volumetric flask, add 200mL of distilled water and 100mL of extractant, shake it on a shaking table for 1h, then add 40mL of sodium hydroxide solution, dilute it to 500mL with distilled water, and filter it immediately.Transfer 60mL filtrate to a 100mL volumetric flask, add aluminum hydroxide emulsion, fix the volume to 100mL, and filter.At this time, the filtrate becomes colorless and transparent.
4. Colorimetry
Suck 40mL of transparent and clear filtrate, transfer it to a 50mL colorimetric tube, and mark the colorimetric tube.Add p-aminobenzenesulfonic acid solution and N-1-naphthylenediamine hydrochloride solution respectively according to the method in step 2, dilute to 50mL, mix well, stand for 15min, observe the change of sample color, compare with the standard color developing solution, find out the color closest to the standard solution, record the corresponding sodium nitrite content, and calculate according to the formula (nitrite content in the sample (mg)/Sample size).
Rescue measures
Name of measures
Detailed measures
Oral medical advice
For acute poisoning events, oral medical advice should be given first for routine treatment, such as oxygen inhalation, retention of venous channels, submission for examination, etc., then medical history should be understood, patients should be examined, and medical records should be established to win rescue time.Do not ask the medical history and write the medical record slowly according to the routine order. It often delays time to start treatment after diagnosis
Oxygen inhalation
Eating pickled vegetables, cooked leftovers, etc. is easy to produce nitrite, and there are criminals fromIndustrial saltThe bulk salt extracted from theOxidantIt can oxidize the normal low iron hemoglobin into methemoglobin, and lose the ability of oxygen delivery to cause tissue hypoxia.According to the observation, the patient's face turned blue, lips cyanosis, and venous blood was blue and purple, all of which were signs of hypoxia. Therefore, oxygen inhalation was immediately given
It's nitrite poisoningspecific antidote It can reduce methemoglobin and restore normal oxygen delivery function.The dosage is 1~2mg per kg of body weight.At the same time, hypertonic glucose can improve bloodosmotic pressure, can increase the detoxification function and have a temporary diuretic effect
Symptomatic treatment
For patients with cardiac and pulmonary functions affected, they should also deal with symptoms, such as respiratory stimulants, arrhythmia correcting drugs, etc
nutritional support
After the condition is stable, give support therapy such as energy mixture and vitamin C
gastric lavage
If the poisoning time is short, gastric lavage should be carried out in time
Sodium nitrite
The common nitrites are sodium nitrite and potassium nitrite. There are many reports of acute poisoning events caused by the misuse of sodium nitrite as table salt in China.Timely remove after treatmentpoison. In addition to oxygen inhalation,antidoteIt is methylene blue (methylene blue), and 200-400ml fresh blood can be transfused for critically ill patients. If necessary, blood exchange therapy can be considered.
Assay
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Determination preparation
Therefore, the nitrite content is determined asFood safety inspectionA very important project in.
Limit standard of nitrite in some foods (with NaNOtwoCount)
Western cooking, smoked ham and canned, canned Western ham
≤70
explain:
① Trace nitrite often exists in domestic drinking water and cannot be used for determinationDiluent。
② If the color is very deep after color development and there is precipitation or it fades into light yellow soon, it indicates that the nitrite content in the sample is very high and must be increasedDilution multipleRe measure.
③ The over standard samples shall be tested repeatedly and sent to the laboratory for accurate quantification when conditions permit.
The shelf life is 18 months at room temperature and in dark. See the packaging for the production date.
Attachment:
Instructions for nitrite fast detection tube:
Method and principle: the quick measuring tube made according to the national standard GB/T 5009.33 is quantitative compared with the standard color card.
Operation method
Rapid detection process of nitrite in table salt
1. Rapid detection of nitrite in table salt and rapid identification of table salt and nitrite: take 1 tablespoon of table salt with a small spoon attached to the bag, add it to the detection tubedistilled waterOr purified water to 1ml scale, cover, shake and dissolve the solid part, and compare with the standard color plate after 10 minutes. The value on the color plate multiplied by 10 is the nitrite content in table salt mg/kg (the national standard stipulates the limit of nitrite in table salt (refined salt)hygienic standard Should be ≤ 2 mg/kg).When the sample appears blood red and precipitation occurs or quickly fades intoyellowIt can be determined that the nitrite content is quite high, or the sample itself is nitrite.2. Liquid sample test: take 1mL of clear liquid sample directly and add it into the test tube, cover it, shake and dissolve the reagent, compare it with the standard color plate 10 minutes later, and find out that it is in the test tubesolutionColor scale with the same color, the value on the color scale is the nitrite content in the sample mg/L (with NaNOtwo).(Milk and soymilk can also be directly tested, and the results should not exceed 0.25mg/L. Colored liquid samples can be added some activated carbon to decolorize and filter for determination).
Determination curve of nitrite content
3. Detection of solid or semi-solid samples: take 1.0g or 1.0mL of evenly crushed samples into a 10mL colorimetric tube, and add distilled water or deionized water（purified water）To the scale, shake it sufficiently and place it. Take 1.0mL of supernatant (or supernatant obtained by filtration or centrifugation) and add it to the detection tube. Cover it, shake the reagent and dissolve it. After 10 minutes, compare it with the standard color plate. The value on the color plate multiplied by 10 is the nitrite content in the sample mg/kg (in NaNOtwo).If the test result exceeds the highest value on the color plate, it can be measured after quantitative dilution and multiplied byDilution multiple(For example, take 1.0mL from a 10mL colorimetric tube and transfer it to another 10mL colorimetric tube, add water to the scale, take 1.0mL from it and add it to the detection tube for determination. The test result multiplied by 100 (times dilution) is the nitrite content in the sample.
Urinalysis
Some bacteria in the urinary system can reduce the protein metabolite nitrate in the urine to nitrite. Therefore, determining whether there is nitrite in the urine can quickly and indirectly know the bacterial infection in the urinary system as a screening test for urinary infection.
Clinicallyurinary tract infectionThe incidence is very high and sometimes asymptomatic, especially in female patients. Urine is needed to diagnose urinary tract infectionBacterial cultureIt takes a long time and certain conditions, and the qualitative test of urinary nitrite can quickly get the results, which is helpful for the auxiliary diagnosis of the disease.
The positive reaction is when the obvious urinary tract infection person uses the characteristic of bacteria that can reduce nitrate to nitrite to produce red phenol coupling.
The positive rate of urinary nitrite depends on the retention time of urine in the bladder for more than 4 hours. The positive rate can reach 80%. If the urinary tract infection bacteria cannot reduce nitrate to nitrite, or the retention time of urine in the bladder is short, or the urine is lack of nitrite, a negative result will also be produced. The positive result will indicate that the number of bacteria in the urine is more than 100000/ml.
When the urine nitrite test is negative, it does not mean that there is no bacterial infection, but that the urinary system infection caused by some bacteria that do not have the ability to reduce nitrate cannot show positive. Such bacteria include non fermenting bacteria such as Acinetobacter or urine cannot be retained in the bladder for more than 4 hours.
Note that negative results can also be produced if the urinary tract infection bacteria cannot reduce nitrate to nitrite, or the urine remains short in the bladder or the urine lacks nitrate.
preventive measure
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1. Vegetables should be properly stored to preventPutrefactionDon't eat rotten vegetables.
2. The leftover cooked dishes are not allowedhigh temperatureStore for a long time before eating.
3. Do not eat a large amount of newly pickled vegetables. When pickling, put more salt, and marinate for at least 15 days before eating;However, it is better to eat the pickled vegetables right away rather than store them for too long. Fresh vegetables are used for pickling.
4. Don't eat a lot of leafy vegetables in a short time, or blanch them with boiling water for 5 minutes, and then cook them after abandoning the soup.
5. The amount of nitrate and nitrite in meat products should be strictly in accordance with the national health standards and should not be added too much.
6. Bitter well water shall not be used for porridge cooking, especially for overnight storage.
7. Prevent nitrite from being used as salt or alkaline surface by mistake.
8. Take more vitamin C and vitamin E, as well as fresh fruits.
9. Soak vegetables in boiling water for 3 minutes before eating, and soak potatoes in 1% salt water or vitamin C solution for one day and night[4]。
1. Replenish liquid, especially boiled water or other transparent liquid;
2. Supplement those lost due to vomiting and diarrheaelectrolyte, such as potassium, sodium andglucose；
3. Avoid antacids;
4. Don't stop diarrhea first, let the toxins in the body drain and thendoctorconsultation;
5. No need to induce vomiting;
6. Eat a light diet. Eat foods that are easy to digest first, and avoid foods that are easy to stimulate the stomach.
In view of the above reasons, the state has established strict limit standards for nitrite residues in food. However, because high concentrations of nitrite can not only improve the sensory color of meat products, but also greatly shorten the processing time of meat products, it is common for meat products to exceed the limit of nitrite.Even a small number of illegal operators passed through with sick or dead pork firsthydrogen peroxide solutionSoak and bleach, then add a lot of nitrite, and finally process to reach normalmeat productColor effect;In addition, cured meat with a large amount of nitrite added can reach the color and hardness of normal smoked and roasted for more than ten days as long as it is smoked and roasted overnight, and it is "exceptionally bright".
How to reduce the intake of nitrite and nitroso compounds
·Eat more fresh vegetables and meat.
·Keep food at low temperature to reduceProteolysisAnd nitrite.
·Do not eat cured products, sausages, sauerkraut, etc.
·Do not eat pickles that have been pickled for about 7 days, and eat less pickles that have been pickled for 15 days.
·Spices such as pepper and pepper are packed separately from salt.
·The grain is often exposed to the sun to decompose nitroso compounds.
·Vegetables and fruits rich in vitamin C and vitamin E.
