Nattō

Natto typically is eaten on rice

Nattō topped with karashi mustard and Welsh onion

Nattō (なっとう or 納豆) is a traditional Japanese food made from soybeans fermented with Bacillus subtilis var. natto.^[1] Some eat it as a breakfast food.^[2] 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.^{[3][4][5][6][7]} In Japan nattō is most popular in the eastern regions, including Kantō, Tōhoku, and Hokkaido.^[8]

History

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.^[9] 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.

Appearance and consumption

Opening and stirring a container of nattō

Nattō has a distinctive smell, somewhat akin to a pungent cheese. Stirring nattō produces lots of sticky strings.^[1]

Nattō is occasionally used in other foods, such as nattō sushi, nattō toast, in miso soup, tamagoyaki, salad, as an ingredient in okonomiyaki, or even with spaghetti. Sometimes soybeans are crushed and fermented. This is called 'hikiwari nattō'.

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. A 2009 internet survey in Japan indicated 70.2% of respondents like nattō and 29.8% do not, but out of 29.8% who dislike nattō, about half of them eat nattō for its health benefits.^[10]

Production process

Soybeans in a plantation

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 increase their size. Next, the soybeans are steamed for 6 hours, although a pressure cooker may be used to reduce the time. The beans are mixed with the bacterium Bacillus subtilis, known as nattō-kin in Japanese. From this point on, care must to 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 Natto-making facilities, these processing steps have to be done by 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 soy beans.^[11]

To make nattō at home, a bacterial culture of B. subtilis is needed. B. subtilis natto is weak in lactic acid, so it is important to prevent lactic acid bacteria from breeding. Some B. subtilis natto varieties that are more odorless are usually less active, raising the possibility that minor germs will breed. Bacteriophages are dangerous to B. subtilis.

Historically, nattō was made by storing the steamed soybeans in rice straw, which naturally contains B. subtilis natto. The soybeans were packed in straw and left to ferment.

End product

Nattō is sold in small containers with small packets of soy sauce and mustard.

Today's 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.

Natto has a different nutritional makeup from raw soy beans, losing Vitamin A and several other vitamins and minerals. The calorie content of natto is lower than that of raw soy beans, however. While soy beans are highly nutritious, the nutrition is packed in the bean's hard fiber. Natto includes the benefits of nutritious soy and softer dietary fiber without the high sodium content present in many other soy products, notably in miso. Natto contains no cholesterol and is a significant source of iron, calcium, magnesium, protein, potassium, vitamins B6, B2, E, K2, and more.^[12][13] When Natto is mixed with egg and eaten with rice, Japanese call the dish a perfectly nutritious meal, covering all nutritional needs. Natto is the richest food source of natural K2. Consumption of it is strongly associated with bone health.^[14]

When Bacillus subtilis natto breaks up soy protein, the bacteria creates chains of polyglutamic acid, Gamma polyglutamic acid. This polypeptide chain is unusual in that the peptide bond is found between the nitrogen and the R-group's carboxyl acid.^[15]

Nutrition

By mass, natto is 55% water, 18% protein, 11% fats, 5% fiber, and 5% sugars.^[16]

A serving of natto (100g) provides 29% of the Daily value (DV) of Vitamin K, 22% of the DV for Vitamin C, 76% of the DV for manganese, 48% of the DV for iron, and 22% of the DV for dietary fiber.^[17]

Close relatives of natto

Many countries produce similar traditional soybean foods fermented with Bacillus subtilis, such as shuǐdòuchǐ (水豆豉) of China, cheonggukjang (청국장) of Korea, thuanao (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.^[8][18]

In addition certain West African bean products are fermented with the bacillus, including dawadawa, sumbala, and iru, made from néré seeds or soybeans, and ogiri, made from sesame or melon seeds.

Gallery

• 
  A nattō bean-size legend using beans before fermentation in a supermarket
• 
  Natto being stirred with chopsticks
• 
  Nattō gunkan maki (Nattō sushi)
• 
  Nattō wrapped in rice straw, old style nattō package

See also

• Amanattō – beans sweetened with sugar
• Shiokara – another sticky fermented Japanese seafood
• Oncom – Indonesian slimy fermented soy
• Corn smut
• Fermented bean paste
• Japanese cuisine – 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

References

Wikimedia Commons has media related to: Natto (category)

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