Foods like sauerkraut have been around since ancient times and spread all over the world. When prepared properly, sour kimchi is safe and delicious, and the lactic acid bacteria and lactic acid in it can improve appetite, promote digestion, and benefit gut health. However, if the production process goes wrong, sour pickles may be contaminated with pathogenic bacteria, and there may be excessive nitrite (excessive consumption can lead to poisoning), and even nitrosamine carcinogens.
How Fresh Vegetables Become Sour Pickles
Before there is no pure strain and "Kimchi water" that has been successfully made, the vegetables are directly put into a jar (or a pond or a vegetable pit) to be compacted, and after being marinated for a period of time, it becomes a sour pickle. This process is called Natural fermentation. Naturally fermented bacteria are lactic acid bacteria that come with vegetables on the surface. They use a small amount of sugar and amino acids in vegetable juice to produce lactic acid, forming a sour taste.
Because these lactic acid bacteria cannot decompose macromolecular proteins, safe sour kimchi tastes fragrant and has no odor. They also don't break down cellulose and pectin, and don't damage the cell wall structure of vegetables, so successful kimchi has a crispy texture without stickiness. If the sour kimchi is smelly and sticky, it means that the fermentation process has not been able to inhibit the bacteria well, and the safety is also worrying.
Of course, some people "just like that" and like pickles that smell a bit stinky. In fact, not every miscellaneous bacteria is pathogenic, whether it will bring health risks depends on luck. If nitrosamines (which are carcinogens) are produced due to the action of miscellaneous bacteria, its safety risks will take many years to appear.
How Lactic Acid Bacteria Stand Out
Vegetable raw materials have not been sterilized, and there are various bacteria on the surface, not only lactic acid bacteria. Why is lactic acid fermentation in the end?
Indeed, when the vegetables first entered the pickle jar, lactic acid bacteria did not dominate at all. When pickling vegetables, after placing the vegetables in a jar or pool, use a heavy object to compress them. "Compacting" has two important meanings, one is to squeeze out the air in the gap, and the other is to squeeze out a little vegetable juice. Especially after adding salt and squeezing it, it is easier to squeeze out the vegetable juice. These vegetable juices are nutritious. Although the sweetness of vegetables is not obvious, they generally contain 2% to 5% of soluble sugar, as well as potassium, magnesium and various amino acids and vitamins. Seeing such good food, all kinds of bacteria will naturally swarm and grow wildly. At this time, lactic acid bacteria are not dominant in the surging "bacteria tide". Those bacteria that like oxygen, because aerobic oxidation produces more energy, the growth rate is particularly fast.
However, lactic acid bacteria also have their own specialties - patience. Since the vegetables are compacted, there is not much air left, and the mouth of the container has been sealed, and oxygen cannot enter, so the oxygen is quickly used up. Those miscellaneous bacteria that began to grow rapidly gradually failed to multiply due to lack of oxygen, and their successors were weak. What if there is no oxygen? It has to be anaerobic fermentation, which is another specialty of lactic acid bacteria. It will ferment glucose into lactic acid and release a little energy. Because lactic acid fermentation produces less energy, the proliferation of lactic acid bacteria is relatively slow.
In fact, there are some bacteria that can produce acid in the miscellaneous bacteria, but their ability to tolerate acid is not as good as that of lactic acid bacteria. As the jar becomes more and more sour, the oxygen is gradually depleted, and most of the bacteria feel that they "can't live anymore" and are gradually suppressed, and most of them are heading towards the end of their lives. After a few days or ten days, lactic acid bacteria finally came to the fore and became the most dominant strain in the kimchi jar. At this time, we can breathe a sigh of relief, because after the lactic acid bacteria are on the top, the sour kimchi is safe.
If there is always oxygen, the miscellaneous bacteria are always lively, and the dishes are not safe. Therefore, when pickling vegetables, the water should cover the vegetables, and do not expose them to the air. The sides of the pickle jars must be sealed with water. This is a key measure to prevent oxygen from entering.
"Nitroso Peak" in Sour Pickles
When pickling pickles, there is a lot of oxygen and nutrients, and various bacteria multiply in large quantities. At this time, pickles are very unsafe. Many miscellaneous bacteria can produce nitrate reductase, which will make the nitrite content in the dish rise rapidly, and a "nitrous peak" will appear.
Within 2 to 8 days after the vegetables are put into the kimchi jar, the activity of miscellaneous bacteria is vigorous, and the specific time depends on the vegetable variety, fermentation temperature, salt content, other ingredients and other factors. However, the duration of the "nitrous peak" is not long. As oxygen depletes and acidity rises, these bacteria gradually decline, while lactic acid bacteria do not produce nitrite. Therefore, after the lactic acid bacteria multiply, the nitrite production is very small.
However, nitrite has been formed in sour kimchi, what should I do next? Under acidic conditions, especially when the pH value is below 4, the formed nitrite will continue to decompose. The stronger the acidity, the faster the decomposition and the lower the nitrite content. At the same time, lactic acid bacteria itself contains nitrite reductase, which will also reduce the content of nitrite. In the end, it will be reduced to a safe level that is completely harmless to health. It's usually safe to put it in about 14 days, and in winter, you can wait until 20 days to be on the safe side.
In short, as long as the kimchi is sour enough, as long as the lactic acid bacteria in it dominate the world, there is no need to worry about the problem of excessive nitrite.
How to Reduce Nitrite
Studies have shown that adding ingredients such as vitamin C, garlic, onion, ginger, fresh peppers, or adding antioxidants such as flavonoids can effectively reduce the nitrite produced during the fermentation process when making sour kimchi.
In fact, if you wait patiently for more than ten days, after the acidity is high enough, the nitrite content will naturally decrease. However, some people are very impatient and want to feast on their mouths after just a few days of marinating. This is the time when the nitrite content is at its highest, which is very dangerous. So, it's important to add some nitrite-inhibiting ingredients. The pickling time of Korean kimchi is very short, but adding a lot of garlic and pepper, and also adding fruits, can effectively inhibit the activity of bacteria and improve the safety of the product.
Some studies have found that if you are concerned about the safety of sour kimchi products, adding some vitamin C-rich foods or vitamin C supplements with meals will also effectively reduce the amount of nitrite absorbed by the body. Vitamin C is a reducing agent, and nitrite has strong oxidizing properties. When the two meet, a redox reaction will occur, turning nitrite into nitric oxide and nitrogen.
Experiments have confirmed that adding vitamin C to the finished sour kimchi can greatly reduce the content of nitrite. Another study found that under the condition of simulated gastric juice, after adding vitamin C, the concentration of nitrite gradually decreased over time, and at most nearly 90% of nitrite could be eliminated.
If you also like to eat sour kimchi, please pay attention to the following tips.
1. When buying sour kimchi, choose a product with a fragrant taste and a crisp texture, which is relatively safe.
2. When making sour kimchi, be sure to isolate oxygen and seal the jar so that lactic acid bacteria have the opportunity to become the main flora.
3. After the vegetables are in the altar, don't be impatient, wait for a few more days, and then open and eat after the "nitros peak" has passed.
4. Add onion, ginger, garlic, pepper, pepper, vitamin C and other ingredients during production to reduce the amount of nitrite produced.
5. If you are worried, you can eat sour kimchi with vegetables and fruits rich in vitamin C.
In addition, sour kimchi is suitable for people with loss of appetite, indigestion, anemia, calcium deficiency, etc. Lactic acid itself is conducive to the absorption of calcium, iron, zinc and other minerals. However, people with hyperacidity and gastroesophageal reflux are not suitable for eating more sour kimchi.
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