Eating sour kimchi nitrite intake too much?
eat with it
Recently, the problem of pickling sauerkraut was exposed because of the "3.15 Party", and many friends worry about whether kimchi can be eaten safely.
In fact, foods such as sour kimchi, if done well, are both safe and delicious. The lactic acid bacteria and lactic acid contained in them are even beneficial to health, which can help improve appetite, promote digestion, and protect intestinal health; if not done properly, it may contaminate Pathogenic bacteria, or excessive nitrite, or even produce nitrosamine carcinogens.
Therefore, for such a type of food, we must not "kill it with one stick", but should popularize the knowledge of reasonable production, and strengthen the supervision of the safety and quality of related products.
This article will introduce the basic principles of making sour kimchi. Because you understand the scientific principles, you will naturally know how to make and eat them reasonably.
How did fresh vegetables become sour pickles?
Safe sour kimchi, fragrant and odorless
Before there is no pure strain and no kimchi water that has been successfully made, the vegetables are directly put into a jar (or a pool or a vegetable pit) and compacted. After a period of boredom, it becomes sour kimchi. Fermentation".
Where do naturally fermented bacteria come from?
It is the lactic acid bacteria on the surface of vegetables. They use a small amount of sugar and amino acids in vegetable juice to produce lactic acid, which also produces 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, so successful kimchi has a crisp texture without stickiness.
So, what if it smells bad and sticky?
That is the bad thing about the dry bacteria, which means that the bacteria are not well inhibited during the fermentation process, and the safety is also worrying.
Of course, people in some areas "just like that" and like to eat pickles that are a little stinky.
In fact, not every type of miscellaneous bacteria is pathogenic, whether it is safe or not depends on luck.
If the action of miscellaneous bacteria produces nitrosamines, although it is carcinogenic, it will not work after a few bites, and it will take many years to show its safety risk.
Lactic acid bacteria are good at anaerobic fermentation
It's "superior" sour pickles are safe
Having said that, the vegetable raw materials have not been sterilized, and there are various bacteria on the surface, not only lactic acid bacteria?
Why does lactic acid fermentation take place in the end?
This is a good question.
Indeed, at the beginning, lactic acid bacteria were not dominant at all among the various fungi in Wuyang and Wuyang.
After placing the dish in the jar or pool, it should be compacted.
This compaction 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, the vegetable juice will come out easily.
These vegetable juices are nutritious.
Although the sweetness of vegetables is not obvious, they also contain 2%-5% of soluble sugar, which also contains nutrients such as potassium, magnesium, various amino acids and vitamins.
With such good food, all kinds of microorganisms will of course swarm and grow wildly.
At this time, lactic acid bacteria are not dominant in the surging bacteria tide.
It stood on tiptoe and saw that there were too many top-ranked microorganisms...especially those bacteria that like oxygen, because aerobic oxidation produces a lot of energy, and their growth rate is also very fast.
However, lactic acid bacteria have patience.
The vegetables were pressed very hard, there was not much air left, and the top was sealed again, so that oxygen could not enter, so the oxygen was quickly used up.
Those miscellaneous bacteria that grew rapidly at the beginning gradually felt that the "hypoxia" could not proliferate, and the successor was weak.
What if there is no oxygen?
Anaerobic fermentation is required, which is something that lactic acid bacteria are better at.
It will ferment the glucose into lactic acid, releasing 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, but their ability to tolerate acid is not as good as that of lactic acid bacteria.
As the jar became more and more sour and the oxygen was gradually depleted, most of the bacteria felt that they "simply cannot survive", so they were gradually suppressed, and most of them even died.
In this way, after a few days or even a dozen days, lactic acid bacteria finally came to the fore and became the most dominant bacteria in the kimchi jar.
At this point we breathed a sigh of relief.
Because lactic acid bacteria are "up", sour kimchi is safe.
What if there is always oxygen?
That's trouble.
If the miscellaneous bacteria are always lively, the dishes are not safe.
Therefore, the vegetables should be submerged in water, not exposed to the air, and the sides of the kimchi jar must be sealed with water, which is a key measure to prevent oxygen from entering.
Pickled kimchi at first is the least safe
Allow 14 days for nitrite to decompose
As mentioned earlier, at the beginning, there was a lot of oxygen, sufficient nutrients, and various miscellaneous bacteria proliferated wildly. At this time, it was actually very unsafe.
Because many miscellaneous bacteria can produce "nitrate reductase", the nitrite content in the dish will rise rapidly, and a "nitrous peak" will appear.
The time frame for the vigorous activity of miscellaneous bacteria is usually within 2-8 days after the start of production, depending on factors such as vegetable variety, fermentation temperature, salt content and other ingredients.
However, the duration of the "nitrous peak" is not long.
These bacteria gradually decline as oxygen depletes and acidity rises.
The "good bacteria" of lactic acid bacteria do not produce nitrite.
So, by the time lactic acid bacteria become the climate, nitrite production will be minimal.
But what about those nitrites that have already formed?
The answer is: Under acidic conditions, especially below pH 4, the already formed nitrite will continue to decompose.
The stronger the acidity, the faster it breaks down, so the content is lower and lower.
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.
Usually it is safe to put it in about 14 days. In winter, you can wait until 20 days to be safe.
In short, as long as the kimchi is sour enough, as long as there are lactic acid bacteria in it, we don’t need to worry about the problem of nitrite.
When making pickles, sauerkraut, and kimchi
What can I add 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 amount of nitrite produced during the fermentation process when making kimchi.
In fact, as mentioned above, if you wait patiently for more than ten days, after the acidity is high enough, the nitrite content will decrease by itself.
However, some people are very impatient and want to eat after a few days of marinating/soaking.
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.
For example, the pickling time of Korean kimchi is very short, but adding a lot of garlic and chili peppers, and also adding fruits, can effectively inhibit the activity of bacteria and improve food safety.
When eating sour kimchi
What can I eat with something to feel more at ease?
If you are still worried about the product itself, adding some vitamin C-rich foods or vitamin C tablets with meals will also effectively reduce the amount of nitrite absorbed by the body.
This is because 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.
To sum up, with regard to the food safety of sour kimchi, it is enough to remember the following:
1. When buying sour kimchi, choose the ones with fragrant taste and crisp texture, which are relatively safe.
2. When making homemade sour kimchi, you must pay attention to isolating oxygen and sealing the jar so that lactic acid bacteria have a chance to become the mainstream.
3. Don't be impatient when making it, wait a few more days, and open it after the nitrous peak has passed.
4. Add onion, ginger, garlic, pepper, pepper or vitamin C and other ingredients during production to reduce the production of nitrite.
5. If you are worried, you can eat sour kimchi with vegetables and fruits rich in vitamin C.
Finally, I would like to remind everyone that sauerkraut and kimchi are suitable for people with loss of appetite, indigestion, as well as people with anemia and calcium deficiency.
Lactic acid itself is conducive to the absorption of calcium, iron, zinc and other minerals.
However, people with hyperacidity, as well as people with gastroesophageal reflux, are not suitable for eating more sauerkraut and kimchi.
Text/Fan Zhihong (director of the Chinese Nutrition Society, chief expert of science communication hired by the China Association for Science and Technology)