Making Miso

Mashing cooked soybeans

It is now the middle of winter here in Japan and time again to make another year’s supply of miso. The deep flavour of miso soup (misoshiru) remains for many in Japan a daily dish. Traditionally the first meal of the day consisted of a steaming bowl of miso soup, a bowl of rice, and a selection of pickled vegetables. It is an excellent breakfast that will likely see a resurgence with the demise of industrialized agriculture and global food transportation.

The current trend for bread breakfasts (fluffy, sweet, white bread), the wheat for which is mostly imported, is occurring at a time when Japanese farmers are receiving subsidies to grow less rice! The health cost of this dietary shift will, no doubt, also soon become apparent. The simple diet of whole grains, fermented beans – in the form of miso, shoyu (soy sauce) and natto – vegetables, seaweeds, fish and very small quantities of meat has served the Japanese well for hundreds of years. The Japanese have the longest life expectancy of any nation in the world and, most importantly, in general remain in good health well into their final years.

Mixing koji and salt

Miso is now enjoyed throughout the world and is widely recognized as a healthful, nourishing addition to the diet. It is also easy to make so we can all enjoy wholesome homemade miso made from local organic ingredients.

Mixing koji and soybeans

A nitrogen fixer, the soybean is an excellent plant to grow to help maintain fertility in the garden. An old practice, less common now but still in use in some parts of Japan, is to grow soybeans around the edge of the rice paddy. The two plants are believed to make good companions, particularly as regards their mutual influence on insect levels. They certainly go well together as a meal!

Although soybeans are the traditional ingredient of miso, almost any legume can be used. I have sampled excellent miso made from chickpeas, lentils and fava beans.

Forming mixture into balls

Miso is made by combining cooked soybeans or other legumes with the koji mould (Aspergillus oryzae). The koji is typically grown on rice and is often available from Asian food markets in this form. It is also possible to purchase koji culture which can then be grown on to a medium such as rice, barley, other grains or legumes. Unfortunately domesticated koji is not an easy mould to keep going (unless you have a sterile lab to work in) so with either of these methods it will be necessary to purchase more koji each time you wish to make miso. Even so, it will be much cheaper (and more fun and satisfying) to buy koji and make your own miso than it will be to buy packaged miso. (In Japan there are traditional methods of “wild fermenting” miso, without the addition of domesticated koji, which I will discuss in a future post).

Throwing balls into fermentation vessel

Miso comes in a wide variety of flavours. Altering any step of the process — any ingredient or the ratio of ingredients, the length of time the miso is left to mature — will give a distinctive colour and flavour to the finished product. In Japan such differences have become regional specialities: the island of Kyushu is known for its barley miso (koji is bred on barley rather than rice), the Tokai region for using no grains at all (breeding the koji on beans), and in Nagoya a dark deep flavoured miso is made by maturing the miso for three years. Using more koji will produce a sweeter miso, left to mature for longer the miso acquires a deeper flavour.

Mixture flattened and salted

Basic miso recipe (makes 5kgs):

Special equipment needed:

Fermentation vessel (pottery, enamel, glass or food grade plastic).


  • 1.3 kg soy beans (or other legume)
  • 1.8 kg koji
  • 650 g salt
  • water


  1. Soak soybeans overnight before cooking. The heat source used for cooking will alter the flavour of the finished product as will the water source. In Japan it is believed that wood fires and spring water produce the best miso. Cook the beans until very soft. After cooking strain the soybeans and keep the water for later use.
  2. Mash the cooked soybeans and place in a large mixing bowl.
  3. Mix koji with 50 grams salt.
  4. Mix koji through mashed soybeans.
  5. Water left over from cooking the soybeans is now slowly added to the soybean/koji mixture to achieve a good consistency. The consistency is tested by forming the mixture into a ball and throwing it against a hard surface. If the ball cracks up or crumbles the mixture is too dry, if it splatters everywhere it is too wet. After achieving the correct consistency all of the mixture is rolled into balls.
  6. The fermentation vessel should be cleaned with white alcohol or strong antiseptic herbal tea.
  7. Throw the balls into the pot. The aim here is to remove any air pockets within the pot. When all the mixture is in the pot press to form a flat surface.
  8. The remaining salt (600 grams) is now sprinkled over the surface, especially around the edges as this is where uninvited moulds will first make their appearance.
  9. Cover with bamboo leaves or cling film – again taking care to cover the surface right up to the edges – to help prevent moulds from forming.
  10. Wait. The miso can be eaten after six months (if made during the warmer months) but it will be better if left for longer. Often it is left to ferment for one, two or even three years before consumption. As with most fermentation processes temperature is an important factor. Starting your miso in autumn it will likely need more than six months before consumption. During warmer times of the year the fermentation will be faster but so will the chances of competing moulds moving in. Check your fermentation vessel regularly and remove any moulds appearing on the surface. Even if a layer of mould covers the entire surface the miso below should be fine. Just scrape off the surface to a sufficient depth where only mould free miso can be seen.

Finished miso