Nitrite is produced during the pickling process, so we can’t eat a single bite of kimchi?

Pickles are a traditional Chinese food. The most authentic way to make pickles is to use lactic acid bacteria to ferment radishes, peppers, ginger, and vegetables in a high-salt environment to produce a unique flavor. However, if they are not properly stored, bacteria and mold will multiply, causing the entire jar of pickles to completely deteriorate and become inedible. At the same time, there is another very important and unavoidable common chemical component that is bound to be produced when pickling pickles, and that is nitrite.

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Oh my god! Nitrite? Isn't that poisonous? Then, the kimchi culture that we have inherited since the Wu Ding period of the Shang Dynasty more than 3,100 years ago, while satisfying our taste buds, has also harmed us for more than 3,000 years? Don't panic, listen to our detailed explanation of the changes in nitrite in kimchi, I believe it will dispel your concerns.

Nitrate is an inorganic compound widely found in nature. It is a common chemical component naturally found in various vegetables, including the kimchi we often eat. Vegetables absorb nitrogen fertilizers or nitrogen from the soil when they grow and convert it into nitrate. When we pickle kimchi, the nitrate in the vegetables is converted into nitrite by the "nitrate reductase" in the bacteria.

Ingestion of large amounts of nitrite in a short period of time may cause acute nitrite poisoning, leading to methemoglobinemia, headache, dizziness, fatigue, chest tightness, shortness of breath, palpitations, nausea, vomiting, abdominal pain, diarrhea and other symptoms. In severe cases, it may even lead to coma, respiratory failure and death [1]. What is more worrying is that nitrite reacts with amines after protein decomposition in the stomach acid environment to produce nitrosamines with extremely strong teratogenicity and carcinogenicity, which are a class of carcinogens announced by the World Health Organization. Of course, the intake of any substance must reach a certain amount and exceed the normal metabolic level of the body before it can cause or induce specific diseases such as cancer. In other words, although nitrite can cause cancer, it is not unacceptable.

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The nitrite content in kimchi is not constant, but has a process of "rising first and then decreasing". Usually, the nitrite content will reach its peak two to three days to ten days after pickling, and may exceed 100 mg/kg. But after this period, its content will gradually decrease, and generally drop to below 20 mg/kg after 20 days, which is in line with the provisions of the National Food Safety Standard Limits of Contaminants in Food (GB2762-2017)[2]. After 30 days, it can usually drop to around 3 mg/kg. In order to reduce the harm of nitrite in kimchi, we can take some measures. For example, extend the fermentation time and try to eat it after 20 days to one month of pickling; use pure lactic acid bacteria powder for fermentation to avoid mixing with other bacteria to produce too much nitrite; keep it sealed to prevent other bacteria from entering; refrigerate at low temperature to delay the production of nitrite; try to eat less diving vegetables, that is, kimchi that is pickled for a very short time, such as one or two days; you can also use kimchi instead of salt to stew or stir-fry vegetables[3], which can not only supplement nutrition with fresh vegetables, but also reduce salt intake.

Although the lactic acid bacteria in kimchi have their benefits, they are mainly found in the kimchi brine, and kimchi is high in salt, so it is not suitable to supplement intestinal probiotics by eating more kimchi. In contrast, fermented foods such as yogurt and cheese are healthier choices.

In short, nitrite in kimchi does pose health risks, but as long as we properly control the pickling time and eating method, we can effectively reduce these risks. If kimchi is eaten in moderation, it can still be a delicious dish on the table.

References:

[1] Pay attention to children’s food safety issues: Stay away from nitrites Zeng Yongfang, Guangxi Guigang City Center for Disease Control and Prevention - Shanxi Science and Technology News - 2024-04-02

[2] Anti-poisoning safety tips 2012 - Baidu Library

[3] Kimchi Edible Knowledge - Originality Document

Source: Chongqing Science Writers Association

Author: Zhou Xiaoyuan, chief technician of Tongliang District Center for Disease Control and Prevention, Liu Mengzhe, trainee technician, and Zou Jingbo, chief technician of Zou Teacher Science Garden

Audit expert: Li Hanbin

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