Shoyu Soy Sauce

As a truly versatile seasoning, shoyu can be used in almost any dish from any cuisine: Japanese, of course, but also Chinese, Asian, and European savory dishes. It can even be used with sweets and desserts. Traditional shoyu is made with just four simple ingredients: whole soybeans, wheat, sea salt, and water. Three things distinguish Mitoku’s shoyu from mass produced, commercialized soy sauce: the use of wholesome soybeans, the lack of artificial preservatives, and the method of production, explained here.

  • Organic Kanazawa Shoyu

    • Organic
    • Kosher

    Available in bulk only

  • Organic Adachi Shoyu

    • Organic

    Available in bottle and bulk

What is Koji ?

Koji, the fermentation starter without which shoyu cannot be made, is made with a culture (sometimes also referred to as a fungus), Aspergillus oryzae. This is called koji-kin or koji-kabi in Japanese. Shoyu koji is made by adding the culture to a mixture of steamed and mashed soybeans and roasted wheat (no wheat used for Mitoku’s tamari production). This is koji-making stage, which is the most crucial process in the shoyu production process. Koji is always very rich in enzymes, generated by the bacteria in Aspergillus oryzae, and these enzymes start to break down the raw materials. Then koji is added to the remaining ingredients for the shoyu (or whatever is being made), where the enzymes work as a fermentation starter, launching the critical fermentation process. Koji is one of the key ingredients for many quintessential Japanese seasonings and ingredients, including shoyu, tamari, miso, and mirin, as well as for sake, too. Aspergillus oryzae is nature’s chef, imparting shoyu, and many other fermented foods with their distinct taste, complexity, and aroma, as well as heightening their health benefits.

Fermented foods made which harness the effects of similar cultures can be found across Asia, but only traditional Japanese fermented foods use Aspergillus oryzae. This is because this powerful yet delicate culture can only thrive in optimal conditions—of temperature and humidity—which are found in Japan’s hot, humid climate. Indeed, Aspergillus oryzae is so vital to the production of traditional fermented foods—and therefore to everyday life in Japan—that it has been described as Japan’s “national culture”.

How to store soy sauces

Before the bottle is opened, soy sauce can, in principle, be stored for long periods without spoiling, but it is still better to consume shoyu fairly quickly. Once opened, soy sauce will oxidize on contact with air, so it is important to re-seal the bottle tightly and store in a cool, dark place. In the home, open bottles of soy sauce are best stored in the refrigerator.

Since shoyu is a fermented soy food, like miso, it shares many of miso’s medicinal and nutritional properties while avoiding the problems associated with unfermented soy foods. (See Miso Health Benefits.) Scientists have given particular attention to the high concentration of “brown pigment” in shoyu, because of its strong anti-oxidant and anti-cancer properties. Shoyu is said to aid in the digestion of grains and vegetables while being rich in several minerals. Shoyu is an excellent substitute for salt in all types of cooking.

Mitoku’s shoyu is made with just four simple ingredients – whole soy beans, whole wheat, salt, and water – which are transformed into a delicious seasoning with an appetizing aroma and deep, rich color. The protein content of whole soybeans, the main ingredient, imparts shoyu with its rich umami, while whole wheat gives the seasoning sweetness and its distinctive fragrance. Salt works to protect shoyu from bacteria and also influences the fermentation process, and pure, fresh water is critical for good taste.

Traditionally produced shoyu is the result of a series of carefully-controlled processes, namely preparation, koji-making, fermentation, maturation, pressing, heating, filtering, and bottling. Some of the key processes are outlined below.



This stage is perhaps the most critical in the shoyu production process, as it will shape the taste and quality of the entire batch: you cannot make good shoyu without good koji.

First, whole soy beans are soaked in water then steamed; producers must rely on their years of experience to determine the optimal volume of water and length of steam. Once steamed, the soy beans are mixed with roasted wheat, inoculated with the spores of a culture called Aspergillus oryzae, and left in a special room for a few days to allow the culture to propagate. The temperature and humidity of the room is monitored and controlled to ensure that the resulting koji is optimal for its task, which is to start the fermentation process. Knowing when the koji is ready is the role of the experienced shoyu producer.

Fermentation and Maturation

The next stage is to add both koji and salted water into large wooden tanks. The salt halts the propagation of the koji, and instead the enzymes generated by the koji get to work on breaking down the whole soybeans and whole wheat. The fermentation environment is rich with microorganisms, including lactic acid bacteria and yeast, and each plays its role in promoting fermentation. With the ingredients now broken down, the shoyu is left to mature, allowing it to slowly take on the rich flavor, deep color, and complex aroma of Mitoku’s shoyu.

Since it is living microorganisms which drive this stage of production, each batch of shoyu can differ slightly from those before and after it. To ensure consistency in quality, however, is something that can be achieved through producer expertise. It is the responsibility of the producer to decide when the mixture should be stirred, a process which supports the work of the microorganisms, by keeping a watchful eye on both the mixture itself and any seasonal and temperature changes. The length of the fermentation and maturation process will differ depending on each producer. This stage is followed by pressing, heating, filtering, and finally bottling, before shipment.

In any type of cooking style, traditional shoyu, such as that offered by Mitoku, can enhance and deepen flavors.

Shoyu works to enhance flavors regardless of cooking stages, be it in preparation, during cooking, or at serving. Shoyu can be used with any type of cuisine, bringing an appetizing aroma, depth of flavor, and color to almost any dish. This is down to shoyu’s unique balance of the five basic tastes (sweet, sour, salty, bitter, umami), which is the result of the fermentation process by which it is made.

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