Natto

Nattō (なっとう or ^?) is a traditional Japanese food made from soybeans fermented with Bacillus subtilis var. natto. Some eat it as a breakfast food. It is served with soy sauce, karashi mustard and Japanese bunching onion. Nattō may be an acquired taste because of its powerful smell, strong flavor, and slimy texture. In Japan nattō is most popular in the eastern regions, including Kantō, Tōhoku, and Hokkaido.

Sources differ about the earliest origin of nattō. The materials and tools needed to produce nattō commonly have been available in Japan since ancient times. It has been described as likely being an ancient food. There is also the story about Minamoto no Yoshiie who was on a battle campaign in northeastern Japan between 1086 AD and 1088 AD when one day they were attacked while boiling soybeans for their horses. They hurriedly packed up the beans, and did not open the straw bags until a few days later, by which time the beans had fermented. The soldiers ate it anyway, and liked the taste, so they offered some to Yoshiie, who also liked the taste. It is even possible that the product was discovered independently at different times.

One significant change in the production of nattō happened in the Taishō period (1912–1926), when researchers discovered a way to produce a nattō starter culture containing Bacillus subtilis without the need for straw. This simplified production and permitted more consistent results.

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Wikipedia