The practice of vinegar can be divided into solid method and liquid method. 1. There are three traditional solid vinegar brewing processes: 1. Daqu vinegar production: sorghum is used as the main raw material, and after low-temperature saccharification and alcohol fermentation with enzymes secreted by Daqu, half of aged vinegar grains are put into a fumigation tank, heated with slow fire, and then the other half is added for leaching. Finally, after three days of drying and ice fishing aging, the new vinegar is made into vinegar with deep color, thick texture, mellow sour taste and special flavor. The famous is Shanxi mature vinegar. 2. Xiaoqu vinegar making: glutinous rice and rice are used as raw materials, and microorganisms such as Rhizopus and yeast in Xiaoqu (also known as wine medicine) are used to cultivate bacteria on rice grains in solid state for saccharification and fermentation. Add water and wheat starter, and continue saccharification and alcohol fermentation. Then wheat bran was mixed into the mash to form a solid state, and then high-quality vinegar grains were added as seeds, and the propagation of acetic acid bacteria was gradually expanded by solid-state layered fermentation. After aging with vinegar, the vinegar juice is leached by leaching method, mixed with fried rice yellow and white sugar, clarified, and heated to boil to obtain balsamic vinegar. The famous one is Zhenjiang balsamic vinegar. 3. Using bran as the main raw material, using glutinous rice or Polygonum hydropiper juice to make vinegar mother for acetic fermentation, and aging the vinegar residue for one year to make bran vinegar with unique flavor. The famous ones are Sichuan Baoning (now Langzhong County) bran vinegar and Sichuan Quxian Sanhui specialty vinegar. The solid vinegar brewing process uses wild microorganisms in nature, so the fermentation cycle is long, and the fermentation of acetic acid needs to be turned over, which is labor intensive. At present, there are pure cultured bran koji as saccharifying agent, adding pure cultured yeast koji for alcohol fermentation, and then adding vinegar mother made of pure cultured acetic acid bacteria for acetic fermentation to produce vinegar. There is also an enzyme liquefaction ventilation reflux method. The raw materials were soaked in water, ground into pulp, added with bacterial α-amylase, heated and liquefied, then added with bran koji for saccharification, cooled the saccharified mash, and added with distiller's yeast for alcohol fermentation. After alcohol fermentation, the fermented mash, bran, chaff and vinegar mother are fully mixed and sent to an acetic acid fermentation tank with a false bottom. There are ventilation holes under the false bottom, which allow air to enter naturally and use naturally. The yield, vinegar yield and labor productivity of enzymatic liquefaction ventilation reflux method are higher than those of traditional method. Second, there are many traditional liquid vinegar brewing processes: 1. Rice is used as raw material, steamed in a vat and naturally moldy, then added with water to become liquid, and fermented at room temperature for 3-4 months. After the mature vinegar mash is pressed, clarified, disinfected and sterilized, the finished product with bright color, fragrant smell, no pungent and sour taste and mellow taste is obtained. The famous is ginger rose rice vinegar. 2. Using glutinous rice, red rice and sesame as raw materials, natural liquid fermentation was carried out by adding in stages, and after three years of aging, white sugar was added at last to get the finished product. The famous is Fujian monascus vinegar. 3. Thin wine is used as raw material, and acetic acid is used to ferment in a packed rapid brewing tower, such as white vinegar in Dandong, Liaoning. The new technology of submerged fermentation is gradually adopted in vinegar production by liquid fermentation. After liquefaction, saccharification and alcohol fermentation of starchy raw materials, the wine mash is sent to the fermentation tank, and then the acetic acid bacteria liquid which is gradually expanded by pure culture is inoculated. The product temperature and ventilation rate are controlled to accelerate the oxidation of ethanol to generate acetic acid and shorten the production cycle. There are many kinds of fermenters, and now self-priming aeration fermenters have been used. It was first used in vinegar production by the Federal Republic of Germany in the early 1950s, and it was called Frings acetic acid fermentor, with patent 1969. Japan and European countries have adopted it. China has been using it since 1973.