Some time ago, the food safety problem of soy sauce really attracted people's attention, and also triggered people's thinking and learning about the type, content and additives of soy sauce. Then, the so-called "firewood, rice, oil, salt, soy sauce and vinegar tea" is also a necessary condiment for daily cooking, and vinegar cannot be ignored. How to choose vinegar? What are the key indicators of vinegar? So, let's chat with you today. Vinegar making is a very long chemical reaction process. The principle of making vinegar from grain is to first steam the grain (the microorganism can digest it only after it is cooked and cooked with water), inoculate mixed strains (koji), use a variety of amylases secreted by the microorganism to turn starch in the grain into sugar (saccharification), and then use yeast anaerobic fermentation to make sugar into alcohol (ethanol), and then use acetic acid bacteria to turn alcohol into acetic acid. This chemical reaction process has been learned by middle school students. Therefore, theoretically speaking, making vinegar is harder than making wine, the process is longer, and the labor consumption is greater. Coarse grains, wheat, rice, potatoes, corn, etc. are the raw materials of vinegar. There are many kinds of raw materials for vinegar, and each place has its own characteristic vinegar. For example, the north traditionally produces various kinds of small grains, such as sorghum, millet, buckwheat, barley, etc., which can be regarded as the main raw materials for vinegar production. Some products also add some starch beans. The mature vinegar with rich taste is the model of the mixed grain vinegar; There are more wheat in the Central Plains, so wheat has become the main raw material for vinegar production; Jiangnan is rich in rice, and mainly uses glutinous rice and rice to make vinegar. The soft and sweet glutinous rice vinegar belongs to this category. Rice is cultivated in Beijing and Tianjin, and rice vinegar made from rice is also very popular. In addition, starch containing raw materials such as potatoes, sweet potatoes and corn can also be used to make vinegar. When making vinegar, bran is often added, which is also beneficial when added in proper amount. Because bran contains a large number of B vitamins and minerals, it is conducive to promoting the growth of vinegar microorganisms, and also conducive to improving the content of micronutrients in vinegar. Fruit vinegar is made of fruit or dried fruit, such as apple vinegar, grape vinegar, persimmon vinegar, jujube vinegar, etc. Fruits and dried fruits are rich in sugar, which just saves the troublesome step of starch saccharification. At the same time, fruit vinegar also adds citric acid, malic acid, tartaric acid and other organic acids contained in the fruit itself. The sour taste is different from that of grain vinegar, and it also brings some fruit aroma, so it is delicious. Some vinegar is made partly or entirely from alcohol. With low alcohol Baijiu or edible alcohol as raw materials, saccharification and alcohol fermentation are omitted, so the speed of vinegar brewing is extremely fast, and it can be completed in two or three days. The vinegar produced in this way has not gone through the complex fermentation process in the early stage and has no "browning" caused by Maillard reaction, so the color is very light and the acetic acid content can be very high. The white vinegar bought on the market is usually made directly with alcohol, or with a small amount of rice and alcohol. The aged vinegar made from coarse cereals and beans has high nutritional value. In the process of vinegar making, B vitamins and minerals such as calcium, iron and zinc in grains can be found in vinegar. This is because most B vitamins like acid