Illustrated Japanese Culture

Miso: beans, kōji and time

味噌（みそ）

Miso is a fermented seasoning paste made with soybeans, salt and kōji. Different kōji ingredients, proportions and maturation methods produce pastes used in soup, sauces, marinades and grilled dishes. Colour is one clue to a miso’s character, but it does not identify the whole recipe.

Rice miso and barley miso still contain soybeans.

Kōji type, colour and sweetness are separate ways of describing miso.

Miso paste is not the same thing as miso soup or dashi.

Start with the kōji ingredient

Rice, barley, soybean or a blend

Rice miso uses rice kōji, barley miso uses barley kōji, and soybean miso uses soybean kōji. All contain soybeans. Blended miso can combine finished misos or use a combination of kōji ingredients.

White, pale and red

Ingredients, proportions, cooking and maturation all affect colour. Browning includes reactions between sugars and amino acids. Red miso is therefore not necessarily soybean miso, and a darker paste is not a dependable measure of salt content.

Regional examples overlap

Shinshū is associated with pale, relatively salty rice miso; Sendai with red rice miso; Kansai with white miso; Kyushu with barley miso; and the Tōkai region with soybean miso. Producers in these regions also make other types.

What happens during production

Cooked soybeans

Rice koji

Salt

Mixed soybean paste

An ingredient combination for rice miso.

Prepare beans and grow kōji

For rice miso, soybeans are washed, soaked and cooked. Rice is steamed, cooled and inoculated with kōji mould. The resulting rice kōji is then mixed with the prepared beans and salt. Soybean and barley misos require their corresponding kōji processes.

Koji enzymes break down ingredients
Fermentation and maturation
Flavour and colour develop

Enzymes and microbes develop the paste

Kōji supplies enzymes that break down ingredients; yeasts and other microorganisms also take part during fermentation and maturation. Time and temperature affect aroma and taste. Producers mix, inspect and package the paste according to the product they are making.

Proportions change the result

At comparable salt levels, a higher proportion of kōji generally produces a sweeter miso. Grain, beans, salt and maturation conditions work together, so colour alone tells little about the balance of sweetness and saltiness.

From earlier ferments to packaged seasoning

Ancient records of related seasonings
Wider medieval culinary use
Regional and commercial development in Edo Japan

Earlier fermented foods and changing names

Miso is related to older East Asian fermented foods such as jiang and fermented beans. A term written 未醤 appears in the legal tradition of 701, while the spelling 味噌 appears in the Heian period. The earlier preparations should not be treated as identical to every modern miso.

Household production and portable food

Miso use and household preparation expanded during the medieval period. This concentrated seasoning could be stored and carried, and also served as provisions in the age of warfare.

Detail of a brewing scroll depicting methods passed down from Edo times; the scroll itself is undated.

Cities created markets for regional producers

Edo’s population and food businesses created demand for miso from areas including Mikawa and Sendai.

A 1940 price list for soybean miso and tamari, Nagoya City Museum.

Factories and household packs

Modern factories increased production and introduced new packaging. Hikari Miso, founded in 1936, began building a new factory in 1955 and adopted 20-kilogram cardboard packaging in 1960. Smaller household packs and seasoned products now sit alongside plain paste.

Choose the product for the dish

Dissolve in soup

Use as a coating for grilled rice balls

Soup is one use among several

Miso can season a soup, become part of a sauce, coat food before grilling or be used in pickling and marinades. Name-miso is a category eaten as a relish or side dish. A product labelled dashi-iri already contains stock ingredients.

Read the pack after opening

Low temperatures and less exposure to air help slow changes in colour and flavour. Follow the product’s instructions for storage after opening. Some misos are treated or contain added alcohol to limit yeast activity, so fermentation does not automatically mean living yeasts remain in the pack.

What can you now explain?

Does rice miso contain soybeans?

Yes. Rice refers to the kōji ingredient, not the entire recipe.

What distinguishes barley miso?

It uses barley kōji alongside the other ingredients.

Is red miso always soybean miso?

No. Colour and kōji type are different classifications.

Does darker miso always contain more salt?

No. Colour also depends on ingredients, cooking and maturation.

What does kōji do?

It supplies enzymes that break down ingredients during production.

Why do misos taste different?

Their ingredients, proportions and maturation conditions differ.

Was ancient 未醤 identical to today’s miso?

It belongs to the earlier history of fermented seasonings; exact equivalence should not be assumed.

What is dashi-iri miso?

Miso with stock ingredients already added.

Can miso be used without making soup?

Yes, including sauces, marinades, pickles and grilled-food coatings.

Does every miso contain living yeasts?

No. Processing and ingredients vary; read the specific product information.

Sources and images