Research on kimchi reveals the reasons for the formation of nitrite in kimchi and its pattern of elimination and growth. Nitrate and nitrite are chemical substances widely present in the natural environment, and contain more nitrate and nitrite in vegetables after picking. Vegetables in the pickling and storage of the initial period, the nitrite content is low, but due to the nitrate reductase action of miscellaneous bacteria (Enterobacteriaceae bacteria and fungi, etc.) at the beginning of fermentation, a large number of nitrates in vegetables are converted to nitrites, so that the content of nitrites increases sharply. With the reduction of oxygen in the fermentation system, the growth of lactic acid bacteria leads to a decrease in pH, the propagation of stray bacteria is limited or even dead, and lactic acid bacteria gradually evolve into the dominant flora. Due to the lactic acid produced by the metabolism of lactic acid bacteria and the lactic acid bacteria's own enzyme system, a considerable portion of nitrite was degraded, and also weakened the ability to reduce nitrate. By the end of fermentation, the nitrite content is reduced to the lowest point or even disappears. So from the whole process of lactic acid fermentation of kimchi, the fermentation process nitrite content changes will appear a nitrite peak, which is unavoidable.

Sources of nitrite

1, nitrite in food as a coloring agent and preservative.

2, from the conversion of nitrates added to food.

3, vegetables, especially converted from unfresh vegetables.

Toxicity hazards

Infantile methemoglobinemia (also known as orthohemoglobinemia): excessive nitrate intake can induce infantile methemoglobinemia, due to the large number of nitrites in the body and the combination of hemoglobin in the blood, so that the level of methemoglobinemia rises, due to the inability of methemoglobinemia to bind to oxygen, which is when the person is hypoxic, with the clinical manifestations of the lips, fingernails cyanosis, skin The clinical manifestations of hypoxia are cyanosis of lips and nails, purple spots on the skin and other symptoms of hypoxia, which can lead to death. Often occurs in the drinking water in the nitrate content of high areas, mostly in infants.

Infant congenital malformation: nitrite can enter the fetus through the placenta, 6 months within the baby is particularly sensitive to nitrates, the fetus has a teratogenic effect.

Enlarged thyroid: some studies believe that high nitrate intake can reduce the body's digestion and absorption of iodine, which leads to goiter, but whether nitrate is the direct cause of human goiter, there is still to be further evidence.

Cancer: the use of nitrite coloring, nitrite and meat in the amine reaction, the generation of nitroso compounds, or in the acidic environment for the intestinal tract into nitrosamines, these nitroso compounds are carcinogenic factors.

Preventive measures

1, vegetables should be properly preserved to prevent decay, do not eat rotten vegetables.

2. Leftover cooked vegetables should not be stored at high temperature for a long time before consumption.

3, do not eat a lot of freshly pickled vegetables, pickled vegetables salt should be put more, at least pickled to more than 15 days before eating; but now pickled vegetables, it is best to eat right away, can not be stored for too long, pickled vegetables when the choice of fresh vegetables.

4, do not eat a lot of leafy vegetables in a short period of time, or first blanch in boiling water for 5 minutes, discard the soup before cooking.

5, the amount of nitrate and nitrite in meat products should be strictly in accordance with national health standards, do not add more.

6, bitter well water should not be used for porridge, especially do not store overnight.

7, to prevent the wrong nitrite as salt or lye with.

8, more vitamin C and vitamin E, as well as fresh fruit.

9, vegetables before consumption of boiling water soak 3 minutes to deal with, potatoes placed in a concentration of 1% salt water or vitamin C solution soaked for a day and night.