The grade of brewing soy sauce mainly depends on the content of amino acid nitrogen and the length of fermentation time.

For high-salt dilute fermentation:

Amino acid nitrogen ≥0.80g/ 100ml is the special grade.

Amino acid nitrogen ≥0.70g/ 100ml is the first grade.

Amino acid nitrogen ≥0.55g/ 100ml is secondary.

Amino acid nitrogen ≥0.40g/ 100ml is the third grade.

Generally, soy sauce can be classified in the following ways: according to the production process, it is divided into high-salt dilute soy sauce and low-salt solid soy sauce, and the high-salt dilute soy sauce has better quality and taste; It is also divided into brewing soy sauce and preparing soy sauce, in which the prepared soy sauce is also called chemical soy sauce, which may contain bad ingredients. From the index, it can be divided into super-grade, first-grade, second-grade and third-grade soy sauce. Super-grade and first-grade soy sauce has good quality. According to the color of soy sauce, it can be divided into soy sauce and soy sauce. Soy sauce is light in color, while soy sauce is particularly dark, which is not suitable for home use. In addition, there are special uses of soy sauce, such as extra fresh and extremely fresh soy sauce, steamed fish soy sauce for steaming fish, iron fortified soy sauce and so on. The product label of soy sauce must indicate the method of use, that is, cold mixing or cooking with meals, and the products with cold mixing can be eaten raw. It depends on the specific products of each factory.