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.
Using the traditional Japanese process, honjozo, we make what we consider naturally brewed soy sauce. Our naturally brewed soy sauce is made using only four basic ingredients: soybeans, wheat, salt and water. Careful selection is required for these simple ingredients, as they directly influence the flavor and aroma of the soy sauce.
Role of Soybeans
The unique characteristics of soy sauce originate primarily from the proteins contained in soybeans. Soybeans are first soaked in water over an extended period, and then steamed at high temperatures.
Role of Wheat
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.
Roles of Salt and Water
Salt is dissolved in water, and this brine is used to control the propagation of bacteria during the fermentation process and act as a preservative.
Since its foundation, Kikkoman has been using its original Kikkoman Aspergillus, a type of fungus, to propagate koji mold. Koji mold is one of the most important elements in making soy sauce, and plays an essential role in fermenting the ingredients. This activity is the key to the taste of soy sauce.
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.
Pressing Soy Sauce from Moromi
Soy sauce is pressed from aged moromi. During pressing, the moromi is poured into special equipment wherein the mash is strained through layers of fabric, with each layer folded into three sub-layers. After allowing the soy sauce to flow out of the moromi under the force of gravity, the moromi is then mechanically pressed slowly and steadily for about ten hours. It takes a considerable period of time to gradually press the mash in order to produce beautifully clear soy sauce.
Heating to Adjust Color, Flavor and Aroma
The soy sauce pressed from moromi is called “raw soy sauce.” Kikkoman’s plants are filled with a sweet scent resembling fresh fruit: the aroma of raw soy sauce. Raw soy sauce is left in a clarifier tank for three or four days to separate into its various components, with oil floating to the surface and sediment settling on the bottom. The clarified soy sauce is then run through a steam pipe to heat it: the main purpose is to heat the soy sauce, but this process also halts the activity of the enzymes in order to stabilize the quality of the soy sauce. It also serves to adjust the color, flavor and aroma.
During the pressing and clarifying processes, soy sauce cake and oil are generated as byproducts. Both of these resources are reused: the cake for livestock feed, and the oil as fuel for machinery operations.
Heated soy sauce is bottled automatically.
Quality Inspection Conducted for Each Process
Kikkoman pays minute attention to quality control at every stage of soy sauce production. Quality inspections are carried out during every process to ensure that the highest standards are maintained. Inspectors analyze the ingredients and check the color, flavor and aroma of the soy sauce. Kikkoman’s stringent control system upholds the finest, most consistent quality.
Only soy sauce that has passed all necessary inspections is released into the market. Thanks to this meticulous process, Kikkoman Soy Sauce—containing only simple ingredients—is delivered fresh to your table.