In the seventeenth century, soy sauce was produced completely by hand and was extremely difficult work. Today, soy sauce is produced in highly automated plants using cutting-edge technology—yet the core process of natural brewing hasn’t changed for centuries. Naturally brewed soy sauce is made using the following process.
Naturally brewed soy sauce is made using only four basic ingredients: soybeans, wheat, salt and water. Careful selection is required for these simple ingredients.
Soybeans are first soaked in water for an extended period, and then steamed at high temperatures.
Wheat is roasted at high temperatures, and then crushed by rollers to facilitate fermentation.
Salt is dissolved in water.
2. Koji Making
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.
Kikkoman’s 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.
3. Fermentation and Aging of Moromi
The shoyu koji is moved to a tank and mixed with the salt-and-water solution. This mixture is called moromi, a kind of mash, which is then fermented and aged in the tank. It takes several months.
Various actions take place in the tank, including lactic acid fermentation, alcoholic fermentation by yeast, and organic acid fermentation, all of which impart to the moromi the rich flavor, aroma and color that are unique to soy sauce.
4. Pressing and Refining
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 moromi in order to produce beautifully clear soy sauce.
Soy sauce pressed from moromi is called “raw soy sauce”. The Kikkoman plant is filled with a sweet scent resembling fresh fruit: this is 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, 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 color, flavor and aroma.
The heated soy sauce is bottled automatically. 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 natural ingredients—is delivered fresh to your table.