Miso is a traditional Japanese seasoning. It is a thick paste produced by fermenting soybeans with salt and kōji (the fungus Aspergillus oryzae) and sometimes rice, barley, seaweed, or other ingredients. It is used for sauces and spreads, pickling vegetables, fish, or meats, and mixing with dashi soup stock to serve as miso soup, a Japanese culinary staple. Miso is high in protein and rich in vitamins and minerals, and it played an important nutritional role in feudal Japan. Miso is still widely used in both traditional and modern cooking in Japan and has been gaining worldwide interest.
Typically, miso is salty, but its flavor and aroma depend on the ingredients and fermentation process. Different varieties of miso have been described as salty, sweet, earthy, fruity, and savory.
The origin of miso of Japan is not completely clear.
Grain and fish misos had been manufactured in Japan since the Neolithic era (Jōmon period, 14,000–300 BC). These are called jōmon miso and are similar to the early fish- and soy-based sauces produced throughout East Asia.
This miso predecessor originated in China during the third century BC. Hishio and other fermented soy-based foods likely were introduced to Japan at the same time as Buddhism in the sixth century AD. This fermented food was called shi. The beginning of the current origin of miso is mishō or mishou (未醤) in the Nara period (710–794); with hishio still meaning beans. It is believed that the word changed to Misho and then Miso.
In the Kamakura period (1185–1333), a common meal was made up of a bowl of rice, some dried fish, a serving of miso, and a fresh vegetable. Until the Muromachi period (1337 to 1573), miso was made without grinding the soybeans, somewhat like nattō. In the Muromachi era, Buddhist monks discovered that soybeans could be ground into a paste, spawning new methods using miso to flavor other foods. In medieval times, the word temaemiso, meaning homemade miso, appeared. Miso production is relatively simple, so homemade versions spread throughout Japan.