There are two kinds of soy sauce production, one is fermented soy sauce, which is fermented with soybeans in the old way. One is to prepare soy sauce, which is made by adding pigment, salt and other ingredients to amino acid solution. Both are allowed by the state.

Hair is made of protein, which can be hydrolyzed into amino acid solution, but it is forbidden by the state, but it is illegally produced by criminals.