Nattō

Sources differ about the earliest origin of nattō. One theory is that nattō was codeveloped in multiple locations in the distant past, since it is simple to make with ingredients and tools commonly available in Japan since ancient times.[12]

Nattō is 55% water, 13% carbohydrates, 19% protein, and 11% fat (table). In a 50 grams (1.8 ounces) serving, nattō supplies 110 calories and is a rich source (20% or more of the Daily Value, DV) of several dietary minerals, especially iron (33% DV) and manganese (73% DV), and vitamin K (542% DV). Nattō contains some B vitamins and vitamin C in moderate amounts (table).

Nattō has a distinctive odor, somewhat akin to a pungent aged cheese. Stirring nattō produces many sticky strings.[1] The dish is eaten cold with rice, mixed with the included soy sauce or karashi mustard. Other ingredients such as long onion or kimchi are often added.

Nattō is frequently eaten as nattō gohan (nattō on rice). Nattō is occasionally used in other foods, such as nattō sushi (nattōmaki), nattō toast, in miso soup, tamagoyaki, salad, as an ingredient in okonomiyaki, chahan, or even with spaghetti. Sometimes soybeans are crushed before fermenting.

Many find the taste unpleasant and smelly while others relish it as a delicacy. Nattō is more popular in some areas of Japan than in others. Nattō is known to be popular in the eastern Kantō region, but less popular in Kansai.[11]

For those who dislike the smell and texture of natto, "dried natto" and "fried natto" were developed around 1990. The smell and stickiness are reduced, making it easier to eat for those who do not like conventional natto. Another type of fermented soybeans called "Mamenoka (豆乃香)" has also been developed by improving the soybean and natto bacillus varieties to make it less sticky.[20]

Nattō is made from soybeans, typically nattō soybeans. Smaller beans are preferred, as the fermentation process will be able to reach the center of the bean more easily. The beans are washed and soaked in water for 12 to 20 hours to hydrate them, and increase their size.[21] Next, the soybeans are steamed for six hours, although a pressure cooker may be used to reduce the time. The cooked beans are mixed with the bacterium Bacillus subtilis, known as nattō-kin in Japanese. From this point on, care must be taken to keep the ingredients away from impurities and other bacteria. The mixture is fermented at 40 °C (104 °F) for up to 24 hours. Afterward, the nattō is cooled, then aged in a refrigerator for up to one week to allow the development of stringiness.

In nattō-making facilities, these processing steps have to be done while avoiding incidents in which soybeans are touched by workers. Even though workers use B. subtilis natto as the starting culture, which can suppress some undesired bacterial growth, workers pay extra-close attention not to introduce skin flora onto soybeans.[22]

Mass-produced nattō is sold in small polystyrene containers. A typical package contains two, three, or occasionally four containers, each 40 to 50 g. One container typically complements a small bowl of rice.

Nattō odor comes from diacetyl and pyrazines, but if it is allowed to ferment too long, then ammonia is released.[23]

The fermenting of Nattō develops glutamic acid, which is why it has the elusive "savory" umami flavor.

KNT (Kinema-Natto-Thua Nao) triangle, connects the fermented soyabeans across Asia.[24]

Many countries around Asia also produce similar traditional soybean foods fermented with Bacillus bacteria, such as shuǐdòuchǐ (水豆豉) of China, cheonggukjang (청국장) of Korea, thua nao (ถั่วเน่า) of Thailand, kinema of Nepal and the Himalayan regions of West Bengal and Sikkim, tungrymbai of Meghalaya, hawaijaar of Manipur, bekang um of Mizoram, akhuni of Nagaland, and piak of Arunachal Pradesh, India.[3][25]

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  A nattō bean-size legend using beans before fermentation in a supermarket
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  Nattō being stirred with chopsticks
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  Nattō gunkan maki (Nattō sushi)
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  Nattō wrapped in rice straw, old-style nattō package
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  This food is white rice served in a bowl with natto (fermented soybeans) on top
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  Nattō topped with karashi mustard and Welsh onion
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  Nattō is sold in small containers optionally with small packets of tsuyu sauce with and without mustard.

• Oncom – Indonesian traditional fermented dish
• Fermented bean paste – Fermented foods made from ground soybeans
• Japanese cuisine – Culinary traditions of Japan – Other fermented soy foods include soy sauce, Japanese miso and fermented tofu.
• List of ancient dishes and foods
• List of fermented soy products
• List of soy-based foods
• Kinema – traditional Nepalese food made from fermented soybean