Nukazuke

The bed and the pickles

Nukadoko is a reusable bed of rice bran mixed with salt and water into a moist paste. Nukazuke are the vegetables, and sometimes eggs, fish or other foods, that are buried in it and taken out as pickles. Caring for the bed is a separate task from preparing each vegetable. Many households keep their own bed, and some beds are tended for generations for a distinctive flavour.

The bed is a fermenting community, not a single starter. Beds are turned each day to bring in air, and they are described as containing lactic acid bacteria, butyric acid bacteria and yeast. A laboratory study found that its experimental bran and vegetable pairings changed the microbial communities that developed, which says nothing about how to keep a household bed.

Starting and keeping a bed

The method above is one practitioner's, for a 1 kg bed. A new bed is not eaten from at first: scraps of cabbage, carrot or cucumber are buried and thrown away every day and a half to two days for a week, until the bran is soft and spongy, smells noticeably and tastes sour. Raw or roasted bran can be used. A rounded container is easier to turn by hand, and the bed needs a daily turn and a regular taste for salt and sourness.

If the bed turns soggy, more bran and salt are added. If it is not salty enough, 1 teaspoon of salt per 100 g of bran is added and the bed is left at room temperature for 1 to 3 days. Lemon is avoided because its acid stops fermentation, and so are juicy items such as ripe tomatoes that burst. Flavourings vary: kombu, dried shiitake and chili in this formula, and elsewhere sansho, yuzu or apple peel, dried sardines or bonito flakes. Another home formula, 1 kg bran with 130 g salt and 1 L water, is stirred up to twice a day for about 15 days and then kept in the refrigerator.

Pickling in the bed

Vegetables are cut to about the thickness of a cucumber, kept from touching and buried completely. They need about 12 hours at room temperature or 24 hours in the refrigerator, then the bran is scraped off, they are rinsed for a second or two and wiped dry. Cucumber is the classic choice; daikon, eggplant and carrot are traditional, and myoga and okra need no preparation. Cherry tomatoes are pricked 6 to 8 times with a toothpick, corn is cut into 5 cm lengths and steamed or boiled for 5 to 8 minutes, and eggs are boiled for 10 minutes and peeled before burying. Newer additions include cheese and bell peppers.

Nukazuke is eaten with rice, as part of the everyday meal, and in chazuke, green tea poured over rice. A culinary-school class presents the pickles as a meal accompaniment.

Heat, travel and trouble

In summer the bed is kept in the refrigerator, preferably the crisper, where fermentation slows. If the cook is away for 3 days to a week, the pickles are removed, the bed is refrigerated and its surface is covered tightly with plastic wrap. For a longer absence the bed goes into a freezer bag and is frozen; after thawing, moisture is adjusted with extra bran and salt. Hands are washed before mixing, or gloves worn.

A white film on the surface is film yeast, common in hot weather: it is mixed in in small amounts, and if it forms a membrane the surface layer is removed. Red, blue or black spots are mould, and the whole bed is replaced. An off flavour or a bed that is too soft is corrected with bran and salt, or the bed is remade. None of this amounts to a validated cleaning method, maturity test or storage life.

Regional styles and history

Nukazuke became widely available in the Edo period (1603-1868), when better rice milling and rising white-rice consumption in cities produced large amounts of bran. Regional styles differ: Kanto beds are salty and tangy, Kansai beds richer and milder, often with kombu or dried shiitake, and some parts of Kyushu use a lot of chili. In Hokkaido and Tohoku, where cooler weather slows fermentation, a little more salt is added. Two local specialities are heshiko, salted mackerel kept in the bed for a long time in Fukui, and fugu no ko nukazuke in Ishikawa, pufferfish ovaries pickled for several years to make them edible.

A regional report on nukadaki, the bran-simmered fish of Kitakyushu, recounts early seventeenth-century records that mention nuka-miso. The report is local and does not show that those records describe today's vegetable bed, so it is not read as the origin of nukazuke.

What is not established

The sources are practitioner and cultural accounts. They give no universal cleaning method, maturity test or storage life for a bed, and none has been validated as a food-safety procedure. Pufferfish-ovary and long-aged fish nukazuke are specialist foods and are not part of this method.