Miso: white, red and everything between

Find the miso shelf in a Japanese supermarket and you will see what looks like a paint chart. Tubs of creamy ivory, honey gold, sandy beige, russet, chocolate brown, almost black. They are all miso (味噌), and they can taste as different from each other as a fresh cheese from a long-aged one.

For many visitors, miso means one thing: the cloudy soup that comes with a set meal. But miso is really a whole family of ferments, shaped by grain, time and place. Knowing a little about it makes everything from breakfast soup to a bowl of ramen more interesting.

What miso is made of

At its simplest, miso is soybeans, salt and koji (麹), fermented together. Koji is grain or beans that have been cultured with a mould, Aspergillus oryzae, the same mould that is central to sake and soy sauce. The koji supplies enzymes that break down the proteins and starches in the beans into savoury amino acids and sugars. Time does the rest.

What the koji is grown on gives the first big division:

• Kome miso (米味噌), made with rice koji. This is by far the most common kind across Japan, and it covers everything from sweet white to deep red.
• Mugi miso (麦味噌), made with barley koji. It has a gentle, toasty sweetness and is especially associated with Kyushu and other parts of western Japan.
• Mame miso (豆味噌), made with soybeans alone, the beans themselves serving as the koji. It is dark, dense and strongly savoury, and belongs above all to the Tokai region around Nagoya.

Shiro, aka and awase

The other big division is colour, and colour is mostly about time and method.

Shiro miso (白味噌), "white miso", is pale and comparatively sweet. It usually has a high proportion of rice koji to soybeans and a short fermentation, so the sweetness stays prominent and the colour stays light. It also tends to be milder in salt.

Aka miso (赤味噌), "red miso", is darker, saltier and deeper. A longer fermentation gives sugars and amino acids more time to react and brown, building colour and a richer, sometimes slightly bitter flavour.

Between the two lies a broad middle of light yellow-brown miso, the everyday style in a great many kitchens. Shinshu miso from Nagano is the best-known example and one of the most widely sold.

Awase miso (合わせ味噌) simply means "blended miso": two or more kinds mixed together, often a red and a white. Many cooks blend their own at home to get the balance they like, and ready-blended miso is common on supermarket shelves too.

Two famous names

Hatcho miso (八丁味噌) from Okazaki in Aichi prefecture is the most famous mame miso. It is made from soybeans and salt and traditionally aged for a long time in huge wooden vats weighted down with piled stones. The name is usually explained by its home, an old village said to lie eight cho, a traditional unit of distance, from Okazaki Castle. The result is very dark, firm and intensely savoury, with an astringent edge. Dark soybean miso of this kind is a backbone of Nagoya cooking, from miso katsu to miso-simmered udon and the miso-flavoured oden of the area.

Saikyo miso (西京味噌) is Kyoto's sweet white miso, pale and mellow, with a high proportion of rice koji. Its best-known use is saikyo-yaki, fish marinated in the miso and then grilled, which caramelises beautifully. Kyoto households also turn to white miso for their New Year soup, ozoni.

These two sit at opposite ends of the paint chart, and they show nicely how regional taste shapes miso. Broadly, Kyoto leans towards sweet white miso, the Nagoya area towards dark soybean miso, Kyushu towards barley miso, and much of eastern Japan towards rice misos in the light-to-red range. These are tendencies, not rules, and every region has its exceptions.

How miso is used

The most familiar use is miso soup, where miso is dissolved into dashi at the very end. But miso is far more versatile than that.

• Ramen: miso ramen was popularised in Sapporo, where the miso tare is often a blend of several misos, sometimes fried with vegetables in a wok before the stock goes in. See Sapporo miso ramen.
• Marinades: fish, meat and vegetables can be cured in miso, which seasons them deeply.
• Glazes: dengaku (田楽), in which tofu, aubergine or konnyaku is brushed with sweetened miso and grilled.
• Hearty soups: pork-and-vegetable tonjiru relies on miso to pull all those root vegetables together.

If you are buying one tub to start, I would choose a medium rice miso: versatile, forgiving and good in almost anything. Add a sweet white for dressings and a dark miso for stews once you are hooked.

Keep miso in the fridge with the surface pressed flat and covered. It keeps for a long time, though it slowly darkens and deepens as it ages. I like that about it. Miso is one of those foods that quietly reminds you it was made by time as much as by hands.