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Make miso

Not many people make miso at home because it’s a very lengthy process and requires some experience. Nevertheless we will try to explain how to make miso at home.

Ingredients for home made miso

To make miso you need the following ingredients:
  • 400 g whole soybeans
  • 600 ml water
  • 150 g salt
  • 300 g dried rice koji (rice fermented with special moulds, this can be bought are also made at home)

Miso production process

All utensils which you use for the production of miso should be clean and preferably be rinsed with boiling water. These are the steps to make miso at home:
  • Soaking the soybeans - Soak the soybeans during 3 hours in the water. By that time the soybeans should have doubled in size.

  • Cooking the soybeans - Put the soaked beans with the soaking water in a pressure cooker and cook at max pressure during 40 minutes. The soybeans should be soft. Open the pressure cooker and drain the beans in a colander, making sure to recover the soaking water.If you don't have a pressure cooker you will need to boil for about 3 to 4 hours to obtain soft soybeans.

  • Mixing the soybeans - When the beans are still hot, use a potato masher to puree the beans until about one third of the soybeans is still whole. Allow he beans to cool down to 35-40°C. If temperature is too high the koji culture could become inactive.

  • Making miso paste - Take 200 ml of the soaking water (add more water if you don’t have enough of it) and dissolve the salt (except for 2 teaspoon salt which you need in the following step). Add this liquid slowly to the soybeans while mixing stirring continuously. Crumble the koji into the miso mixture and with your clean hands mix until you obtain a smooth mixture.

  • Preparation of miso container - As a fermentation vat use a glazed ceramic cylindrical container of about 5 kg. Make sure that the ceramic container is suitable for food preparations. Rub the inside of the container with 1 teaspoon of salt and add the miso mixture. Level the miso surface and sprinkle 1 teaspoon of salt, this to prevent unwanted moulds and bacteria from spoiling the surface which is in contact with the air. Cover the miso with a round piece of kitchen paper and press it firmly on the miso. Top with a round wooden lid that just fits in the container and some weights (about 3 kg, well washed stones). Cover the container with wrapping paper and tie in place with a string or rubber. Repeat all steps as before to make more batches in the following days and add them to the container (first removing lid and rubbing the inside of the container with about 1 teaspoon salt) until the container is about 80% full.

  • Miso fermentation - The fermentation will start immediately. The container should be place in a clean room with moderate temperatures (15°C – 25°C). The miso will be ready after 6 to 12 months fermentation. During the fermentation some liquid (=tamari) will rice to the surface. If no liquid tamari is seen on the surface then the pressing weight must be increased.
    Each time you want to inspect the fermentation process you will loose quality, so don’t do it when not necessary and not more frequently then once every 2 months. This miso can be kept in the container for a few years.

Traditional Japanese miso production

In Japan miso was traditionally produced in small miso shops. Each miso shop used its own unique process and has its own secrets. Before one can make miso he needs to be educated by a miso master during several years. Typical for these miso shops is that the soybeans are cooked in containers on open fires, that miso is fermented in wooden vats and that no motorized equipment is used. These days there’s a lot of competition from big modern miso factories. Due to optimized fermentation conditions the miso is ready after months instead of years. In Japan most miso produced will end up as miso soup.

Comments (8)

I've just recently discovered this great website.
I've noticed that you give very detailed descriptions of how to make miso, however, I can't seem to find any information about where to buy koji.

Is it possible to find it in Europe?

thank you in advance.

#1 - Lene - 10/23/2013
This Dutch company sells koji:
In the US there is Gemcultures.
#2 - Rob - 10/23/2013
Dear Rob

thank you very much.
I'll look into it.

#3 - Lene - 10/23/2013
koji Europe
getting koji in Europe is not easy, there is a dutch company - Terrasana who sell a genmai koji for ridiculous sums of money. I bought a starter from GEM cultures in USA, for $3 + postage and made tons! An easy and fun process! Noel -
#4 - Noel - 11/16/2013
I was wondering... Is commercial Miso cooked at the end of the process in order to stop the fermentation, or would it still have live Aspergillus oryzae in it?
Could I use old miso as a fermentation starter for a new batch (I cannot find Koji where I live?

thank you ever so much

#5 - Angel - 03/17/2014
Natural miso is a living product containing live bacteria. However, most commercial miso that is packed in glass jars or plastic bags is pasteurized. Even if you can find unpasteurized miso it will not be a reliable source for the Aspergillus oryzae spores.

Koji contains millions of live Aspergillus oryzae spores. The main purpose of Aspergillus oryzae is the production of enzymes that will later digest the soybeans. After you add the koji to the soybeans other ingredients are added such as salt which will kill the mold. Other yeasts and bacteria that can withstand the salt will then grow and enhance the aroma and taste of the miso.
#6 - Rob - 03/18/2014
Where to get koji
You can get them in any Chinese / Asian supermarket. Chinese ferments sticky rice slightly and they use it as desserts. I think they are also called rice leaven in Chinese supermarkets.
#7 - Flora - 04/08/2014
Can I use Miso that I have made to make a new batch
Is it possible to use Miso once prepared to make a new batch the next year or do I have to buy the seed culture every year. Seed culture is quite expensive to get here.
#8 - Joe Harris - 05/03/2014
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