In order to minimize the intake of nitrite, how should vegetables eat?

Everyone may have heard that nitrite can be used for fresh and anticorrosive products such as sausages, cans, but a large amount of intake can cause human poisoning. This substance will be converted into nitrosamine in the body -this is a first -level carcinogen, so even if it is added safely, it is not recommended for everyone for long -term and excessive edible processing meat products.

In addition to the nitrite of food additives, we generally think that green and healthy vegetables and foods. If the eating and storage methods are improper, it will also contain a large amount of nitrite. Among them Foods with high content.

Various types of pickles (picture source: VEER gallery)

Why do these dishes produce nitrite? What are the dangers after eating? Today we will talk about the nitrite problem in vegetables.

How did the nitrite in vegetables come from?

The growth of plants is inseparable from the three large elements, namely nitrogen (n), phosphorus (P) and potassium (K). The farm proverb says: "Nitrogen long leaves, phosphorus fruit", which means that the nitrogen content in the leaves is very high, such as rapeseed, spinach and other leaves, etc. The nitrogen content in fruit vegetables is low.

Nitrogen can exist in plants in a variety of states. Among fresh plants, the main forms of nitrogen elements include ammonium (NH4+), nitric state (NO3-), and free amino acid state (-NH2), etc. There are very few nitrogen elements (NO2-).

Figure 1 Plant nitrogen deficiency can lead to poor leaf development. (Picture source: Flickr-International Maize and WHEAT Improvement Center)

The picking vegetables will not immediately "die", but will also be "stretched" for a long time. However, the plant cannot obtain nutrients and water from the soil, so the picking vegetables began a series of "self -rescue" behaviors.

In this process, the active role of various enzymes in plant cells gradually transforms other types of nitrogen into nitrite. Therefore, as the storage time increases, there will be more and more nitrite in vegetables.

If the vegetables are marinated, the nitrite in vegetables will increase by hundreds and thousands of times in the first period of time, but this is not caused by the self -rescue of plants. In fact, pickled ingredients (salt, etc.) can directly kill plant cells in a short time, and do not give vegetables for self -rescue at all.

After the death of the plant cells, the nutrients are exposed, and a large amount of bacteria in the air will settle on the surface of the plant. These bacteria reproduce a large number of bacteria and convert a large amount of nitrogen in plants into nitrite.

Similarly, cooking will also kill plant cells, so after the vegetables are cooked, it can also cause cell rupture and exposed content. Therefore, the nutrients in vegetables will also attract a large number of bacteria to "enjoy". Experiments show that the concentration of cooking vegetables after cooking has increased significantly, and it can be as high as 55mg/kg when it is stored for more than 48 hours at room temperature. As a reference, the nitrite content in the national standard restricted vegetables is not more than 20mg/kg.

Figure 2 Cooking vegetable cell structure is destroyed, and it is easy to breed bacteria to produce nitrite (picture source: Veer gallery)

How to avoid excessive intake of nitrite?

After knowing the source of nitrite in vegetables, we can reducing the risk of excessive intake of excess nitrite in response to these sources.

First of all, in order to avoid buying vegetables from the "Gou" time, it produces a large amount of nitrite, and we must try to eat fresh vegetables as much as possible. If you buy too much at one time, try to pack it as much as possible and store it in the refrigerator. However, if it is not stored in the refrigerator, it is necessary to remove the packaging to prevent the nitrite of nitrite caused by the breeding of nitrifying bacteria in anaerobic conditions to increase rapidly.

Figure 3 The refrigerator fresh vegetables are stored as much as possible to add packaging (Picture Source: Flickr-Agelia Hardy)

Second, carefully eat pickled vegetables. After the 3.15th program exposed the old altar sauerkraut incident, many people on the social networking site said that they would make kimchi themselves in the future.

After about 10 days of pickling, the mixed bacteria in the dish gradually died, and the produced nitrite was also decomposed by beneficial bacteria. Therefore, it can effectively avoid nitrite poisoning. Pay attention to the salt when marinated, otherwise it cannot effectively kill the fungi.

Figure 4 The effect of fermentation time on the content of kimchi nitrite, I-IV is different fermentation methods, and V is compared. It can be seen that it takes at least 12 days when the level of nitrite content is reduced to the level of non -fermentation. (Image source: References 1)

Finally, you must eat as little leftover.

According to the data in a series of scientific research documents I checked, the nitrite content of nitrite is still increased by the remaining dishes for 24 hours. However, after more than 24 hours, the nitrite content will rise quickly to exceeding the standard. Therefore, the dishes that are not eaten at night, the bento for the second day, but do not stay until the third day.

Figure 5 The changes in nitrite content after storage of vegetables and storage. (Image source: References 2)

Is it safe to put vegetables in the refrigerator?

Because low temperature can significantly inhibit the growth of bacteria, putting the refrigerator can effectively inhibit the increase in nitrite in the remaining vegetables. Save the leftovers without adding packaging, and when saving fresh vegetables, add packaging (packaging box, plastic wrap, etc.), because the cellular structure of fresh vegetables itself is complete and can resist bacteria. The packaging causes a hypoxic environment And steaming. In low temperature environments, most bacteria will be suppressed, but there is a "wonderful" bacteria that likes the low temperature environment, that is, Liszt bacteria.

In the 4 ° C environment, Liste bacteria can still grow and reproduce normally, thereby polluting refrigerated food. Although this kind of bacteria are very visible to pathogenic bacteria, and the infection ability is weak. However, for people with low immunity (pregnant women, children, elderly people, and patients with basic chronic diseases), Liszt bacteria still have a strong disease.

Figure 6 Scan Listera under the electronic microscope. (Picture source: Phil-Elizabeth White)

Not long ago, the media just reported a case of a pregnant woman infected with Liszto, which led to a case of infant premature birth. After the doctor's efforts, the baby born at a 24 -week -old and only 600 grams of babies lived in danger. But this case sounds the alarm again: the leftovers of the refrigerator must not be stored for a long time, try not to let it go for 48 hours, and it must be fully heated before eating!

Here, the office workers with their own lunch are reminded that the heating of the microwave oven is prone to the surface of the food but the inside is not hot, so the heating time must be long enough to ensure that the food is hot.

Image source: veer gallery

In summary, we usually try to eat fresh vegetables as much as possible, do not store too long; the refrigerator stores fresh vegetables to add packaging; scientifically arranges the amount of vegetables according to the number of meals, and try not to leave the left; For more than a day of leftovers, avoid eating.

The older generation often reluctantly throws away the leftovers, but at the same time, the ages of the elderly are weaker, and they are more likely to become the object of infection of Listera. Children should use the truth and case to clarify the harm of eating leftovers and maintain their physical health with practical actions.

references:

1. Li Hanchen, Tian Lixia, Zhao Xiyan. The effects of different treatment methods on the acidity and nitrite content of cabbage fermentation and nitrite [J]. Journal of Hebei Science and Technology Normal University, 2004, 18 (3): 4.

2. Ye Hongyangyang. Hangzhou's preliminary research on the laws and dietary exposure assessment of vegetable nitric acid [d]. Zhejiang Agricultural Forestry University, 2018.

3.gb2762-2012 "Limited pollutants in food safety national standard foods"

4. GB5009.33-2016 "Measurement of Nitrite and Nitrite in Food Safety Standard Food"

5. "Just because of a negligence, 27-year-old pregnant mothers infected with Liste bacteria to give birth to premature babies", Peninsula Morning Post, 2022-3-25

Author: Mu Yunshen

Produced: Popular Science China

Producer: China Science Popularization Expo

The China Science Popularization Expo is the Science Popular Science Platform of the Chinese Academy of Sciences. It is sponsored by the Computer Network Information Center of the Chinese Academy of Sciences. Relying on the high -end scientific resources of the Chinese Academy of Sciences, it is committed to spreading cutting -edge scientific knowledge and providing fun science and education services.

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