1, because vegetables originally contain nitrate, in the pickling process, due to mixed bacteria, nitrate in vegetables is turned into nitrite under the action of nitrate reductase in microorganisms.

2. However, according to different vegetable varieties, the content of nitrite is also high and low. "Generally speaking, the nitrate content of leafy vegetables such as Chinese cabbage and purple cabbage is higher than that of root vegetables such as radish. Therefore, during the pickling process, the converted nitrite is also higher than the latter. " In addition, the pickling method of kimchi and sauerkraut belongs to fermentation. Theoretically, if pickled under ideal conditions, nitrite will not appear in kimchi and sauerkraut. However, because it is inevitable to mix mixed bacteria when making kimchi and sauerkraut at home, there will also be nitrite in kimchi and sauerkraut. "If the same dish is made into kimchi, sauerkraut and pickles under the same conditions, the nitrite content in pickles is relatively higher than the other two."