Making Soy Sauce

Learn all about how Kikkoman Soy Sauce is made.

The state of soy sauce production, which was depicted in the “Koueki Kokusankou” in the late Edo period. (National Diet Library, Japan)

In the 17th century, soy sauce was produced entirely by hand, and as this picture shows, this was extremely hard work. Today, Kikkoman soy sauce is produced in highly automated plants using cutting-edge technology, but the brewing process at its core has not changed for centuries. Kikkoman Soy Sauce is produced using the traditional Japanese brewing method, “honjozo”, described below.

The 4 Raw Ingredients of Soy Sauce

Kikkoman Soy Sauce is made using the traditional Japanese brewing process known as “honjozo”. We call this honjozo method, which makes use of the natural powers of fermentation, “naturally brewed”. Kikkoman Soy Sauce is made from the four basic ingredients of soybeans, wheat, salt and water. Since the components of these ingredients have a direct impact on the flavor of the soy sauce, it is very important to carry out careful selection.

Kikkoman Aspergillus

Since its founding, Kikkoman has carefully protected the original Kikkoman Aspergillus (a kind of koji mold) and continues to use it to this day. Koji mold is one of the most important elements in making soy sauce, and plays a very important role in fermenting the raw materials and then producing the characteristic “color”, “taste” and “aroma” of Kikkoman soy sauce. Kikkoman Aspergillus is the “key” for making soy sauce.

The Kikkoman Soy Sauce brewing process


The unique characteristics of soy sauce are mainly derived from the proteins contained in soybeans. Soybeans are first soaked in water and then steamed at high temperature.


Carbohydrates contained in wheat are the components that give soy sauce its fine aroma; wheat also adds sweetness to the soy sauce. Wheat is roasted at high temperatures, and then crushed by rollers to facilitate fermentation.




Production of Shoyu Koji

Kikkoman Aspergillus is mixed with steamed soybeans and roasted crushed wheat, and then moved to a special location equipped with an optimum environment for the growth of Kikkoman Aspergillus. It is through this three-day process that soy sauce koji, which is the basis of soy sauce production, is made.

Shoyu Koji


Salt and Water

Salt is dissolved in water to make brine. This brine controls the growth of bacteria during the fermentation process, prevents spoilage, and also imparts the salty taste to soy sauce.

After that the mixing process begins. The soy sauce koji is mixed with salt water and transferred to a tank. This mixture, called moromi, is fermented and aged in tanks.

Aging of Moromi

Moromi is aged for several months. Inside of these tanks, and due to the action of microorganisms, various changes occur, including lactic acid and alcohol fermentation, which create the rich flavor, aroma and color unique to soy sauce.



Soy sauce is pressed from aged moromi. Moromi is poured into 3-fold cloths, and folded back into multiple layers. Once the soy sauce flows out from the moromi under the force of gravity, the moromi is then mechanically pressed slowly and steadily for about ten more hours. In order to produce beautifully clear soy sauce, the process must never be rushed.


During the pressing process, soy sauce cake is produced as a by-product. This soy sauce cake is recycled into animal feed for livestock.

Raw soy sauce


The soy sauce pressed from Moromi is called “raw soy sauce”. Raw soy sauce is left in a clarifier tank for about three days to separate into its various components, with oil floating to the surface and sediment settling on the bottom. Only the clarified portion in the middle is extracted. Next, the raw soy sauce is passed through a heating device to heat it. By this process enzymatic activity is halted in order to stabilize the quality of the soy sauce, and it also serves to adjust the color, and aroma.

Quality Inspection

Kikkoman pays close and careful attention to quality control at each step of soy sauce production. Quality inspections are carried out for all processes to confirm that quality is maintained in accordance with standards. An inspector analyzes the ingredients to check the soy sauce for flavor, taste and color. Kikkoman’s strict quality control system maintains the consistent quality of Kikkoman Soy Sauce.


The heated soy sauce is machine packed into containers in a clean environment.