Carbohydrates in kimchi are biodegraded by yeast, lactic acid bacteria and other microorganisms. Under the biocatalysis of various enzymes, long-chain carbohydrates in kimchi are oxidized into short-chain organic acids with 3-5 carbon atoms in microbial cells such as lactic acid bacteria, which makes kimchi acidic to inhibit and kill other harmful spoilage microorganisms. This is the fermentation process of kimchi.

Second, the three stages of pickle fermentation:

1. Early stage of fermentation: When vegetables first entered the jar, the microorganisms with human beings on the surface were mainly acid-resistant Escherichia coli and yeast. Among them, the initial breathing mode of yeast is aerobic breathing. At the initial stage of fermentation, bubbles will be intermittently released from the tank along the water tank, thus gradually forming an anoxic state in the tank and starting lactic acid fermentation.

2. Mid-fermentation period: Due to the continuous accumulation of lactic acid in the initial stage of lactic acid fermentation, the pH decreased, forming an anoxic state, and lactic acid bacteria began to be active, producing a large amount of lactic acid, and the accumulation of lactic acid could reach 0.6% ~ 0.8%, and the pH was 3.5 ~ 3.8. This period is the complete maturity stage of kimchi, which is sour and fragrant.

3. Late fermentation stage: during this period, lactic acid fermentation continued, and the lactic acid content increased continuously, reaching more than 1.0%. When the lactic acid content reaches more than 1.2%, the fermentation speed will gradually slow down or even stop. The main reason is that at present, the acidity of kimchi is too high, the flavor is uncoordinated, and aerobic microorganisms in the tank consume oxygen and produce a lot of carbon dioxide.

Extended data:

Pickle skills:

1, chopsticks caught in pickle jar and pickle jar should not be stained with oil and meat, otherwise the pickle water will "blossom", that is, white mold will grow on the pickle water. When you encounter "flowers", you should use clean utensils to remove mildew, add appropriate amount of pickle salt and liquor, move the pickle jar to a cool and ventilated place, open the lid for 10 minute every day, and it will get better after 2-3 days.

2. If kimchi tastes too sour, you can add some salt; If it is too salty, you can add some sugar; If it's not crisp, you can add some white wine.

3. Pickled peppers must not be soaked in ginger, otherwise the peppers will become soft and hollow.

4. To make kimchi, you must choose kimchi salt (that is, salt without iodine), which is conducive to fermentation. Where pickle salt can't be bought, coarse salt can be used instead. I used coarse salted salt.

5. In addition to the pickle jar, you can also make kimchi in a sealed container, but you must ensure that it is sealed.

6, peppers, vegetables, etc. People who make kimchi must air-dry it and put it in a kimchi jar.

7. Kimchi water can also soak chicken feet, pig feet, pig tails, pig ears and other leeks, but you must not put leeks in kimchi water for a long time. Amaranth should be cooked separately.

References:

Baidu encyclopedia-pickles