Ferment III (Shoyu)

September 20, 2010

Shoyu is a fermented soybean product known to the English speaking world as soy sauce. Although, much of what is sold as soy sauce is not produced  by fermentation at all but is the product of a chemical process using soy extract, ethyl alcohol, sugar, salt, food colouring and preservatives. Tamari, originally a byproduct of the miso making process is now brewed,  using a similar process to traditional shoyu making but without the addition of wheat.

Soybeans are soaked, cooked (boiled or steamed) and left to cool. Cooling is facilitated by dividing cooked beans amongst a number of containers and regularly turning the beans to bring the hot ones below to the surface and fanning those on top. The amounts placed in each container are precisely measured to ensure the correct relative amounts of wheat can be added later.

Wheat is dry roasted. A slow even roasting is achieved by constant stirring over low heat. This can be done in batches and as long as the colour of each batch is similar an even roasting across batches has been achieved.

Roasted wheat, now cooled to room temperature, is mixed with koji (Aspergillus oryzae) and divided into equal amounts relative to the number of batches of soy beans cooling in the containers.

Wheat/koji is mixed through the soybeans. Then the remaining wheat is also added to the mix.

Wheat, koji and soybean mix is spread out onto bamboo trays covered with cotton inside a ‘plastic house’ (the greenhouses typically used by Japanese farmers). The next stage of the process, where the koji mycelium spreads through the bean and grain mix, requires a warm and humid environment, hence, the plastic house.

Magnolia leaves are placed directly on top of the bean/grain mix and these are covered with the edges of the cotton cloth.

Cotton sheets are placed over the trays and straw mats over the sheets.

In two to three days the koji will colonize the bean/grain mix and cover it with a fluffy, fragrant mold mycelium.

The bean/grain/mycelium mix is poured into a brine (sea salt and good quality water) and thoroughly mixed. From this point on the mixture (moromi) will need to be stirred every day for about one year after which it will be stirred every other day for another year. When stirring it is important to keep the sides of the barrel clean as it is here that contamination is likely to occur. The inside of the barrel above the level of the moromi should be carefully wiped down after each stirring.

The new batch in the rear, then a two year old batch and a one year old batch in the foreground. Between stirrings the barrels are covered with cloth.

Following is a description of what is occurring during the aging process.  It comes from the wonderful book Culinary Treasures of Japan: The Art of Making and Using Traditional Japanese Foods by Jan & John Belleme, 1992 (New York: Avery Publishing Group).

[E]nzymes from the koji and the naturally occurring yeasts and bacteria slowly breakdown the complex carbohydrates, proteins, and oils of the wheat and soybeans into sweet sugars, aromatic alcohol, and flavorful amino and fatty acids.

After about two years the moromi is placed in cotton sacks and pressed. The soy oil that rises to the top is skimmed off and you have the shoyu. It is left to settle, pasteurized under  low temperature and bottled.


9 Responses to “Ferment III (Shoyu)”

  1. Jocelyn Says:

    And how does the real thing taste compared to what us peasants are use to…. I know “don’t even try” :-)… did I spot a glimpse of Asako? Looking forward to seeing you! hugs

  2. […] in May I went to a chinju-no-mori in the mountains of Hanamaki to collect magnolia leaves for making shoyu. This particular chinju-no-mori was very large, basically the whole mountain, but, unfortunately, […]

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  6. David Says:

    Great post ! Have you ever come across people using old wine barrels for miso and shoyu tamari production, I live in Australia and can’t find any straight edged barrels.

    • dion Says:

      I haven’t seen them being used but I can’t see why not. Any tainting of the flavour that could possibly occur would be rather pleasant I would imagine. But its unlikely that you would get any hint of wine flavour cutting through the strong flavours of shoyu or miso.

      • David Says:

        Thank you so much for taking the time to reply, I really enjoyed visiting your site over the weekend, keep up the good work, fantastic posts
        Regards Dave

  7. Chris Says:


    thanks for the great post! I am looking for a shoyu recipe – it is kind of hard to find. Especially the proportions (for small scale production aka home 🙂 .

    Maybe you could help me:

    1) What is the proportion (dry weight?) of Soybeans and Wheat for the Koji?

    2) What salt concentration does the brine have (%)?

    3) And how much brine (in l) do you add to the koji (in kg)?

    I am looking forward to your help.


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