There has always been a saying in the health care industry that overnight dishes, especially overnight dishes, can't be eaten in summer, saying that overnight dishes have many bacteria and high nitrite content. \x0d\ is it true? If it exceeds the standard, how serious is it? How about braised pork and braised fish? Are they not up to standard, either? \x0d\ Recently, the reporter came to the laboratory of the Department of Food Science and Nutrition, biosystems engineering College of Food Science, Zhejiang University, and determined the nitrite content in vegetables overnight. The reason why only nitrite content is measured is that heating overnight can kill bacteria in vegetables, but heating can't remove nitrite. \x0d\ Stir-fry four dishes to see how big the problem is \x0d\ In order to measure the nitrite content of overnight dishes, the experimenter asked the chef of a well-known high-end chain restaurant in Hangzhou to cook four dishes: stir-fry, scrambled eggs with leeks, braised pork and braised crucian carp. \x0d\ Shi Rui, the chef of the restaurant, learned that we used it for nitrite experiment and specially selected the freshest ingredients. After the four dishes are finished, the master personally packages them and puts them into four fresh-keeping boxes. Chef \x0d\ Shi said that if leftovers are left for a long time, nutrients will be lost and bacteria will easily breed. People with bad stomachs are prone to diarrhea, which usually happens a lot, so customers are generally advised to finish the packaged dishes within 2 hours. However, chef Shi said that it is not clear whether nitrite will exceed the standard if leftovers are left for a long time. \x0d\ The nitrite content in meat is higher than that in vegetables \x0d\ In order to make people have a more objective understanding of the change of nitrite content in leftovers, the experimenter deliberately divided four dishes into four parts, put them into disposable degradable lunch boxes, wrapped them with plastic wrap, and marked them for half an hour, six hours, 18 hours and 24 hours respectively. Then, put these samples into the laboratory refrigerator and refrigerate at 4℃, which is also the temperature set by ordinary household refrigerators. \x0d\ The experimenter first grinds the plate into slurry, weighs 1g (note: g g g) sample, puts it in a conical flask, and dilutes it with distilled water. Let it stand in the dark for 15 minutes, and directly read the nitrite content with a fast detector. In order to ensure the accuracy of the test results, each sample is tested three times, and finally the average value is taken. \x0d\ Half an hour after cooking, the test results of scrambled eggs and braised pork with leek showed that the nitrite content did not exceed the highest limit in the Limits of Pollutants in Food in China, that is, 4mg/kg for vegetables and 3mg/kg for meat (note: mg mg, kg kg). However, the nitrite content in braised pork is higher than that in fried eggs and vegetables with leeks. The experimenter said that meat dishes generally add more seasonings than vegetables, and the seasonings themselves contain nitrate, which is converted into nitrite by microorganisms, resulting in higher nitrite content in braised pork. \x0d\ The nitrite in braised pork exceeded the standard first \x0d\ 6 hours later, it was almost the time interval from lunch to dinner. It is common for many elderly people or families with two employees to eat cooked dishes at noon and at night on rest days. \x0d\ The experimenter opened the refrigerator, took out the stir-fried dishes marked "6 hours", scrambled eggs with leeks, braised pork and braised crucian carp, and then put them in the microwave oven, heating them with medium and low fire 1 minute. These dishes still look fresh after being taken out of the microwave oven. \x0d\ The experimenter measured the nitrite content in these dishes, and the results showed that after 6 hours, the nitrite content in the leftovers increased, the fried dishes increased by 16%, the scrambled eggs with leeks increased by 6%, and the braised pork increased by 70%. Among them, the nitrite content in braised pork reached 4.2558mg/kg, which exceeded the limit standard of "3mg/kg meat" in the National Limit Standard for Pollutants in Food. \ x0d \ dishes marked "18 hours" are put in the refrigerator 18 hours later, taken out of the refrigerator and heated in the microwave oven for detection. The results showed that the nitrite content in stir-fried dishes increased significantly, by 44.3% compared with 6 hours, by 54% in braised crucian carp and by 47% in scrambled eggs with leeks, while the nitrite content in braised pork did not change much. \x0d\ From this experiment, it can be seen that the nitrite content of fried vegetables, braised pork and braised crucian carp exceeded the national standard when overnight dishes were put at noon the next day. \x0d\ Don't eat the dishes in the refrigerator for 24 hours \x0d\ After four dishes have been cooked for almost 24 hours, the experimenter took out the last batch of four dishes marked "24 hours" from the refrigerator and put them in the microwave oven for heating and testing. \x0d\ The test results showed that the nitrite content of four dishes continued to increase significantly compared with 18 hours, and all exceeded the limit standard of "Limits of Pollutants in Food". Among them, the fried vegetables exceeded the limit by 34%, the scrambled eggs with leeks exceeded the limit by 4 1%, the braised pork exceeded the limit by 84% and the braised crucian carp exceeded the limit by 1465438+. \x0d\ The experimenter said that the nitrite content in meat dishes exceeded the standard 24 hours after cooking, because the seasoning used in pot-stewed dishes contained nitrate, while the protein content in meat dishes was higher. After 24 hours, microorganisms decomposed a large number of protein compounds, which promoted the transformation from nitrate to nitrite. \x0d\ Nitrite content rises rapidly at room temperature \x0d\ In order to understand the changes of nitrite content in dishes after being stored in refrigerator and room temperature, the experimenter also placed the braised crucian carp samples at room temperature for 4 hours, and then determined its nitrite content. The results showed that the average content of nitrite detected three times was 8.9483mg/kg, which was more than double the national limit standard and exceeded the refrigerator for 24 hours. According to Urban Express \x0d\ The more stale vegetables are, the higher the nitrite content is. \x0d\ Associate Professor Shen from the Food Science and Nutrition Research Office of biosystems engineering Department, College of Food Science, Zhejiang University introduced that the nitrite content of raw vegetables was determined in their laboratory before, and it was found that all vegetables contained nitrite, but it did not exceed the national standard. The general trend is that the more stale vegetables are, the higher the nitrite content is, and the nitrite content of those rotten vegetables is more obvious. \x0d\ Nitrite is contained in vegetables because nitrogen fertilizer is applied during the growth of vegetables, and nitrate comes from nitrogen fertilizer. Nitrate is not toxic, but microorganisms in the air will enter leftovers, and microorganisms are more active at room temperature, producing a reductase that can convert nitrate in dishes into nitrite. \x0d\ Teacher Shen said that judging from the nitrite content of raw vegetables, the nitrite content of cooked vegetables is only much higher. "In theory, the longer the leftovers are left, the more intense the microbial activity and the higher the nitrite content. And the nitrite content of different dishes is different. " \x0d\ According to Metropolitan Express \x0d\ Ingestion of 3g nitrite can lead to poisoning death \x0d\ Nitrite can oxidize low-iron hemoglobin in blood into methemoglobin, lose the function of transporting oxygen, and lead to tissue hypoxia and even death. Adults can be poisoned by ingesting 0.2 to 0.5 grams, and 3 grams can be fatal. If eaten for a long time, it will also cause diseases such as esophageal cancer, gastric cancer, liver cancer and colorectal cancer. \x0d\ The Ministry of Health issued an early warning \x0d\ Preventing nitrite poisoning \x0d\ Recently, food poisoning accidents occurred frequently in some places, especially nitrite poisoning and food poisoning in collective canteens. The day before yesterday, the Ministry of Health issued an early warning notice on prevention and control of food poisoning in official website. The announcement calls for strict prevention of food poisoning caused by nitrite and microbial pollution, and further strengthening the supervision of food production, circulation and catering. \x0d\ The chemical food poisoning reported in the first half of this year is mostly caused by eating nitrite by mistake, which is common in canteens and small catering businesses in construction sites. Therefore, the management of collective canteens and restaurants should be strengthened, and it is strictly forbidden to buy and use industrial salt to prevent nitrite from being eaten by mistake. The construction site should strengthen the management of industrial nitrite, and it is forbidden to mix it with other foods and raw materials. Collective canteens and catering industries should use nitrite correctly in strict accordance with the standards for the use of food additives, and excessive and out-of-range use is strictly prohibited. Food safety supervision departments should strengthen supervision over the production and circulation of nitrite as a food additive. \x0d\ In addition, summer and autumn are the high season of food poisoning, especially this year, the temperature and humidity in most parts of China are higher than normal, which makes food and its raw materials vulnerable to microbial contamination. Especially when eating seafood such as fish, shrimp and shellfish. Beware of food poisoning caused by Vibrio parahaemolyticus, and beware of food poisoning caused by botulinum when eating canned, pickled and fermented food. \x0d\ At the same time, the food safety supervision department should strengthen the supervision of food production, circulation and catering to raise public awareness of food safety. Health departments should strengthen the monitoring and reporting of food-borne diseases and find food safety hazards as soon as possible. \x0d\ According to the concept of China News Service \x0d\ water has become carcinogenic water \x0d\ The General Administration of Quality Supervision, Inspection and Quarantine recently announced the results of sampling inspection on the quality of drinking water in bottles (barrels). Among them, six kinds of drinking water were found to be high-concentration carcinogen "bromate", and the "pure" weakly alkaline drinking water produced by well-known enterprises such as Harbin Sixth Pharmaceutical Factory and the "Jingyao" desert high-quality water in Inner Mongolia were famous and shocking. \x0d\ Ordos jingyou Honghu mineral spring drink co., ltd. gained a wide reputation in just a few years by playing the "desert card". The company claims that its products are alkaline "pure natural desert water". However, AQSIQ found that the measured value of bromate in a batch of "Jingyao" bottled water was as high as 8 times the standard value. According to reports, bromate has been designated as a "Class 2B" potential carcinogen by the International Agency for Research on Cancer. Zheng Yushan, a senior engineer of the Institute of Product Quality Inspection in Inner Mongolia Autonomous Region, admitted that most enterprises have limited detection ability for bromate at present, fearing that testing by a third party will increase costs and lead to hidden dangers.