1. According to national standards, the core quality of soy sauce depends on an indicator called "amino acid nitrogen", which must be indicated on the label of soy sauce products. Qualified soy sauce shall not be less than 0.4g/100ml. Generally, the higher the content of amino acid nitrogen, the higher the quality of soy sauce. For example, the amino acid nitrogen of special-grade soy sauce can reach 0.8 g/100 ml, and some fresh soy sauce can even reach 1.2 g/100 ml. When choosing soy sauce, you should choose the one with high content of "amino acid nitrogen".

　　 2. According to national standards, soy sauce products must indicate on the label whether they are "brewed" soy sauce or "prepared" soy sauce. The former is made by using soybean processing by-products as raw materials through fermentation, which is a traditional production method; the latter is prepared by flavoring with "hydrolyzed protein liquid" (sometimes mixed with some brewed soy sauce). Needless to say, "prepared" soy sauce is not as nutritious as "brewed" soy sauce, and it will also contain "trichloropropanol" (has a certain toxicity, but the concentration that meets national standards is harmless). When purchasing soy sauce, you should choose "brewed" soy sauce.

　　3. According to national standards, soy sauce products should also indicate on the label whether they are "cooking" soy sauce or "cooking" soy sauce. The former can be eaten raw directly, so its hygienic index requirements are higher and cleaner; the latter is suitable for cooking dishes (such as braised pork) after heating (equal to disinfection) before eating, so its hygienic index requirements are lower and not as clean as the former. It is possible to cook (heat) dishes with "cooking" soy sauce (equivalent to "high-end low-use"), but it is not advisable to use "cooking" soy sauce to directly cool or dip it (equivalent to "low-end high-use").

　　 4. There are some soy sauces that are "iron-added soy sauce", that is, high-quality soy sauce with "EDTA sodium iron" (sodium ethylenediamine tetraacetate iron) added according to national standards and the requirements of relevant management departments, It is rich in iron, which is helpful for the prevention and treatment of iron-deficiency anemia. It is suitable for everyone, especially for pregnant women, patients with anemia or people with anemia tendency. This blog strongly recommends this kind of soy sauce, please be optimistic about the "specialized label for fortified food" when buying (as shown in the picture above). Iron-added soy sauce is produced on a fixed-point basis and has special standards and strict management. Its safety is the same as that of other soy sauces. Consumers do not have to worry about excessive iron.