Traditional soy sauces are made by mixing soybeans and grain with mold cultures such as Aspergillus oryzae and other related microorganisms and yeasts (the resulting mixture is called "koji" in Japan; the term "koji" is used both for the mixture of soybeans, wheat, and mold as well as for the mold itself). Historically, the mixture was fermented naturally in large urns and under the sun, which was believed to contribute extra flavors. Today, the mixture is placed in a temperature and humidity controlled incubation chamber.[14]
Traditional soy sauces take months to make: