Making Soy Sauce

In the seventeenth century, soy sauce was produced completely by hand, and as this picture shows, it was extremely difficult work. Today, soy sauce is produced in highly automated plants using cutting-edge technology—yet the core brewing process has not changed for centuries. We make what we call naturally brewed soy sauce using the traditional Japanese process, honjozo, described below.


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Production of Shoyu Koji


Kikkoman Aspergillus is mixed with processed soybeans and wheat, and then moved to a facility that provides the optimal environment for propagating koji mold. This three-day process results in the production of shoyu koji—the essential base of soy sauce.


The mixing process starts from here: the shoyu koji is moved to a tank and mixed with the brine. This mixture is called moromi, a kind of mash, which is then fermented and aged in the tank.


Fermentation and Aging of Moromi


The moromi is aged for several months. Various actions take place in the tank, including lactic acid, alcoholic, and organic acid fermentation, all of which impart to the moromi the rich flavor, aroma and color that are unique to soy sauce.