Acetic acid, also known as acetic acid and glacial acetic acid, with the chemical formula CH3COOH, is an organic monobasic acid, which is the main component of vinegar. Pure anhydrous acetic acid (glacial acetic acid) is a colorless hygroscopic solid with a freezing point of 16.6 ℃ (62 ℉). After solidification, it is a colorless crystal. Its aqueous solution is weakly acidic and highly corrosive. Steam has irritating effects on eyes and nose.

Acetic acid can be used as acidity regulator, acidifier, pickling agent, flavor enhancer, spice, etc. It is also a good antimicrobial agent, mainly due to its ability to reduce the pH below the pH required for microbial adaptation to growth. Acetic acid is an earlier and more widely used sour agent in China. It is mainly used in compound seasoning, preparing wax, canned food, cheese, jelly, etc. When used in seasoning, acetic acid can be diluted to 4%~5% solution with water, and then added to various seasonings. The beverage made of vinegar as sour agent and nutritional health products is called the international third generation beverage.

Acetic acid can be prepared by artificial synthesis and bacterial fermentation. Biosynthesis, i.e. bacterial fermentation, accounts for only 10% of the total output, but it is still an important method to produce acetic acid, especially vinegar, because the food safety regulations of many countries stipulate that vinegar in food must be prepared by biological method, and fermentation method can be divided into aerobic fermentation method and anaerobic fermentation method.