How to Make Nukadoko (Fermented Rice Bran Bed) for Pickling

 

Nukazuke (糠漬け) are a type of Japanese pickle, made by fermenting vegetables in rice bran (nuka). Almost any edible vegetable may be pickled through this technique, though traditional varieties include eggplant, Japanese radish (daikon), cabbage, and cucumber. The taste of nuka pickles can vary from pleasantly tangy to very sour, salty and pungent. These pickles also retain their crispness which adds to their popularity. Fish nukazuke is also common in the north part of Japan. SardinemackerelJapanese horse mackerel are frequently used. Some people pickle meat in nuka-bed.

The nuka-bed is traditionally kept in a wooden crock but ceramic crocks or even plastic buckets are also common. Many Japanese households have their own nukazuke crocks which are faithfully stirred by hand every day. Due to varying methods and recipes, flavors vary considerably not only from region to region but also from household to household.

Pickles (tsukemono) are an important staple of Japanese cuisine, and nukazuke are one of the most popular kinds. They are often eaten at the end of a meal and are said to aid in digestion. The lactobacillus in nukazuke pickles may be a beneficial supplement to the intestinal flora. They are also high in vitamin B1.

Preparation

Rice bran is first roasted, then mixed in a crock with salt, kombu seaweed, and water. Some recipes call for ginger, miso, beer or wine. The resultant mash, called nukamiso or nukadoko, has a consistency comparable to wet sand or cooked grits. Vegetables, apple peels, or persimmon peels are added to the nuka-bed every day for at least a few days until a fermenting culture has been established. At this point nuka-bed is ‘live,’ meaning that it contains a culture of active single-celled organisms, mostly lactobacilli and yeast. Although nukazuke can be made from scratch, a bit of well seasoned nuka from an older batch is often used to ‘seed’ a fresh batch.

Unless an established nuka sample is used to seed a fresh batch, the ubiquitous lactic acid-producing colonies crucial to the fermentation process must come from sources such as the skin of the starter vegetables or from human hands.

Once the fermenting cultures have been established the nuka-bed usually develops a complex unique aroma that may be described as anything from “yeasty” to “earthy”. At this point the starter vegetables are discarded and pickling vegetables are buried in the bed for as little as a few hours to as long as several months for very strong flavor. Some sources recommend a maximum pickling time of one month. Others suggest that pickles can be left for years in a well-kept nuka-bed. Unpleasant smells such as a “sour” or “stinky” aroma may indicate a problem with the nuka-bed.

Because the process depends on colonies of live organisms, flavors and smells can vary considerably from day to day and the fermenting process slows in colder weather.

When ready, nukazuke pickles are removed from the bed, washed in cool clean water, sliced and served as a side to savory meals.

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