Too long not to look at the version
Leafy vegetables do have the risk of exceeding the nitrite standard after overnight, especially be wary of spinach, even if refrigerated placed may still exceed the standard.
Spinach is not suitable for children under 3 years old to eat a large amount at a time, and do not use spinach water to flush milk powder.
It is safer to pickle kimchi and sauerkraut for more than 14 days before eating.
Overnight tea, thousand boiling water do not have to worry at all.
In 2022, "overnight" is still a key word active in various pseudo-health articles and love family groups, and anything that stains the word "overnight" will become terrible, such as overnight water, overnight tea, overnight dishes...
Today, I will talk about what exactly is "overnight" and really be vigilant.
Where is the horror of "overnight"?
Rumor has it that the horror of "overnight" is that it will make the nitrite in food soar.
Nitrites are indeed a threat to the human body, both to make us acutely poisoned and to transform into the carcinogen nitrosamines in our bodies.
But we don't just have to dip nitrite, it has to reach enough to hurt us.
The Food and Agriculture Organization of the United Nations and the World Health Organization's Committee on Additives consider nitrites up to 0.07 mg per kilogram of body weight acceptable, even when long-term, chronic effects are considered. [1]
Then according to this limit, if you are a 60kg person, 4mg of nitrite per day is still no problem.
Figure | unsplash
Where does nitrite come from?
Plants like to absorb nitrogen-containing compounds into the body, the most common form is nitrate, nitrate has no direct harm to the human body, but nitrate can be converted into nitrite under the action of enzymes, microorganisms, air and temperature.
Nitrates in the soil can also enter the groundwater, resulting in the presence of a certain amount of nitrate and nitrite in drinking water.
The vast majority of the nitrites we obtain through eating and drinking come from vegetables and processed meat products (additives), and drinking water contributes very little. And we get nitrate from the outside world, which can also be converted into nitrite in our body.
Spinach overnight really have to be vigilant
First, leafy vegetables are at the highest risk
The degree to which vegetables like to absorb nitrates from the environment:
Leafy vegetables> root vegetables> shallots and garlic> melon fruits> beans> nightshade fruits
On the part of the words:
Stems and roots > leaves > fruits
In summary, leafy vegetables are the most risky class of nitrites, followed by rhizomes, and melons, solanum, and legumes are the lowest. [2]
Spinach is a common vegetable that is often mentioned as easily enriched with nitrates.
Fresh leafy vegetables have nitrites on their own, and when you blanch it or sauté it quickly, the nitrite content will decrease. [15]
But if you don't finish eating, the next microbial reproduction will increase the nitrite content in it.
If the leafy vegetables bought home are not cooked, just put them, then with the extension of the storage time, the nitrite in it will become more, the same as cooking and then putting it.
Be especially wary of spinach
The Hong Kong Food Safety Centre found that spinach, chinese cabbage and lettuce are three kinds of vegetables with high nitrate content, and it is easier to produce more nitrite during the placement process. Potatoes, onions, carrots, and tomatoes are low in nitrates. [3]
Figure | Hong Kong Food Safety Centre
Will it exceed the standard after overnight placement?
Experiments have found that even if spinach is refrigerated after cooking, the nitrite content in it will exceed the national standard after 16 hours, and the room temperature will be higher, so spinach is best eaten at one time, do not put it too long.
According to the National Standard for Food Safety Limits of Contaminants in Food (GB 2762-2017), the nitrite content in vegetable products should be less than 20mg/kg
[4-7]
Infants and young children should also pay special attention
Nitrite levels in foods are generally not as acutely toxic to adults, but infants and young children under 6 months of age are different and more sensitive.
Nitrites can change the structure of hemoglobin, resulting in oxygen transport is blocked, and babies may experience hypoxia if they accidentally eat excess nitrate or nitrite within a few months, known as "blue baby syndrome", or cyanosis.
The European Food Safety Authority (EFSA) assesses that eating a large amount of spinach (more than 200 grams) high in one day for children aged 1-3 does not rule out the possibility of poisoning, and recommends that spinach should not be given to infants and young children with bacterial gastrointestinal infections, because in the presence of gastrointestinal bacterial infections, after eating high nitrate foods, more nitrate will be converted into nitrite in the intestine. (Most children's gastrointestinal infections are caused by viruses)[8]
When cooking vegetables, nitrite will dissolve into water, and do not use this vegetable water to make milk powder for your baby. A real incident in October last year was that a parent in Chengdu was afraid that his child would "catch fire", so he used the water left over from boiling vegetables to flush milk powder, and as a result, the child appeared nitrite poisoning symptoms (lack of oxygen, the whole body was blue and purple) after drinking.
Figure | CCTV News Channel October 31, 2021 "Common Concern"
Pickles and sauerkraut are pickled for long enough time to eat
Kimchi and sauerkraut are both foods obtained by fermenting vegetables with microorganisms, and under the action of nitrate reduction bacteria, the nitrates in vegetables will be converted into nitrites faster and more.
So during the kimchi process, there is a time when the nitrite content will be very high, which may be enough to cause an adult to have a toxic reaction.
After this stage, due to the accumulation of acid produced by lactic acid bacteria, the nitrate reduction bacteria are inhibited, and the nitrite content slowly decreases, and the kimchi at this time is safe to eat. Brine concentration and temperature also affect when peaks occur.
[9-10]
Therefore, kimchi must be pickled enough days to eat, it is generally recommended to pickle for more than 2 weeks and then eat, but it is more recommended that people who lack experience and expertise do not pickle their own kimchi, buy regular manufacturers packaged, safe a lot.
Don't worry about overnight tea
Longjing, Pekoe Flower Tea, Anji White Tea, Tieguanyin, Dianhong, Pu'er Raw Tea and Anhua Black Tea 7 kinds of tea, boiling water to make tea (a cup of 140ml of water put tea leaves 2g), after 24 hours of room temperature, the highest nitrite content in tea is Anhua black tea, but it is only 0.27μg/L, less than one thousandth of the safety standard. [11]
According to the National Standard for Food Safety ( GB 2762-2017 ) , mineral water is limited to 0.1mg/L
Studies have found that tea polyphenols, the beneficial substances in tea water, have a certain clearance effect on nitrates.
Although there is no need to worry about nitrites, it is still more recommended to drink the tea after brewing for about 30 minutes, because the tea polyphenols in it are fully leached at this time and the content is the highest. After 30 minutes, the tea polyphenols begin to lose continuously, and by 24 hours, 30% can be lost. [11]
Don't worry about a thousand boiling water
The experiment found that in the process of boiling tap water and pure water every 20 minutes, a total of 30 times, the content of nitrite did rise slowly, but the highest level was 0.025mg/L, far from harming the human body.
In another experiment, the tap water of a school in Beijing was boiled six times repeatedly, and it was also found that the nitrite content was only 10 to the -5th power to the 10th power of 10 to the level of -6 grams per liter.
In addition, after boiling, the amount of nitrite was not significantly increased by leaving the water open for 48 hours. [12-14]
So as long as you use qualified water, you don't have to worry about repeated boiling and causing more nitrite, unless the nitrite in the water source is exceeded at the beginning.
However, the boiled water should not be left for too long, there is still a risk of colonies exceeding the standard.
bibliography
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[2] Salehzadeh H, Maleki A, Rezaee R, Shahmoradi B, Ponnet K. The nitrate content of fresh and cooked vegetables and their health-related risks. PLoS One. 2020;15(1):e0227551. Published 2020 Jan 9. doi:10.1371/journal.pone.0227551
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Huang Runqiu, Chen Gong, He Yunchuan, Yan Zhengcai, Liang Yong, Zhang Qisheng, Li Jiayi, Wang Dongdong, Tang Yao. Effects of raw materials and processes on nitrite content of kimchi[J].Food and Fermentation Science and Technology,2020,56(04):1-5+49.
[11] Li Yiyao,Yang Hongle,Sun Ning,Ban Litong,Huang Liang,Tong Yingkai. Effects of different soaking times on the content of tea polyphenols and nitrites in tea leaves[J].Modern Food, 2020(02):174-177.DOI:10.16736/j.cnki.cn41-1434/ts.2020.02.059.
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This article is reprinted from nutritionist Gu Zhongyi (ID: yy4gz1) with permission, if you need to reprint it for the second time, please contact the original author.