2 Production process

Natto is made from soybeans, usually a special type called natto soybeans. Smaller beans are preferred, as the fermentation process will be able to reach the center of the bean easier. The washed and soaked in water for 12 to 20 hours. This will increase the size of the beans. Next, the soybeans are steamed for 6 hours, although a pressure cooker can be used to reduce the time. From this point on care has to be taken to keep the ingredients away from impurities and other bacteria, except for the bacteria Bacillus natto. The bacteria bacillus natto is a type of hay bacteria and causes the fermentation process. The beans are mixed with a special sauce containing salt, sugar, and yeast with the bacteria bacillus natto. Other ingredients may be added by some manufacturers. The mixture is fermented at 40°C for up to 24 hours. Afterwards the natto is cooled down. The natto is then aged in a refrigerator for up to one week to add the stringiness. During the aging process at a temperature of about 0°C, the bacillus natto will develop spores, and a enzyme called peptidase (old form: protease) is breaking down the soybean protein into amino acid.

Historically, natto was made by storing the steamed soy beans in straw, which naturally contains bacillus natto. The natto was packed in straw and then left to ferment by itself. The fermentation was done either while the beans where buried underground underneath a fire or stored in a warm place in the house as for example under the kotatsu .

3 History

The first production of natto was probably - like so many other inventions - an accident. Someone stored the beans in a package of straw or a sack of rice straw, and did not open the package until the beans fermented. Despite the very strong smell and the spoiled appearance, the product was eaten, probably by a very hungry person. Somehow, this accidental discovery became a mainstream product.

The materials and tools needed to produce natto (soybeans and straw) were commonly available in Japan since ancient times, so the discovery could have happened already in the early Jomon period. It may also be possible that the product was discovered independently by numerous people at different times. The sources differ about the earliest origin of natto. One source puts the first use of natto in the Jomon period between 10,000 BC to 300 BC. Another story is that Yoshiie Minamoto was on a battle campaign in northeastern Japan between 1056 and 1063 and another campaign between 1086 and 1088 when one day in 1083 they got 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, at which time the beans had fermented. The soldiers ate it anyway, and liked the taste, so they offered some to their commander Yoshiie Minamoto who also liked the taste. A third source calls the origin of natto fairly recent from the Edo period ( 1603 to 1867).

One significant change in the production of natto happened in the Taisho period ( 1912 - 1926), when researchers discovered a way to produce the natto yeast containing the bacillus natto without the need for straw. This greatly simplified the production process and enabled more consistent results.

4 Medical benefits

Natto is claimed to have many medical benefits, and Japanese often say that eating natto is good for your health. Some of these claims are backed by medical research. Natto for example contains an enzyme Pyrazine, which not only gives natto its distinct smell, but also reduces the likelihood of blood clotting. Another enzyme nattokinase also reduces the likelihood of blood clots. This helps to avoid thrombosis as for example in heart attacks, pulmonary embolism, or strokes. However, some sources mention that this effect would be undesirable with patients that have a problem with bleeding as for example internal bleeding or patients with haemophilia (Bleeder). An extract from natto containing nattokinase is also available as a dietary supplement. The effect of natto to reduce blood clots has been shown in numerous medical studies.

Natto also contains large amounts of Vitamin K, involved in the formation of calcium-binding groups in proteins, which helps the formation of the bones and prevents osteoporosis. Vitamin K1 is found naturally in seaweed, liver and some vegetables, and vitamin K2 in fermented food products like cheese and miso. Natto has very large amounts of vitamin K2, 870 microgram per 100 g natto.

Natto also contains many chemicals that seem to help prevent cancer, as for example daidzein, genistein, infrabin phytoestrogen, and selenium. However, most of these chemicals can also be found in other soy bean products, and not all of them are conclusively proven to help preventing cancer.

Some sources also claim that natto has a cholesterol-lowering effect.

Natto is also said to have an antibiotic effect, and was used as medicine against dysentery by the Japanese military before World War II. Furthermore, natto is said to improve digestion, reduce the effects of aging, and prevent obesity, although this seems to be based only on an analysis of the chemicals contained in natto, but not on a medical study.

Natto is also sometimes used as an ingredient of pet food, and it is claimed that this improves the health of the pets. The animals also don't seem to mind the smell and sliminess of natto.

5 See also

• Cuisine of Japan
• Culture of Japan

Other fermented soy products are for example Tempeh and Miso. Note that amanatto is not natto, but rather, beans sweetened with sugar.

6 External links

• Nattoland
• Natto for Everybody Homepage
• Nutrition facts of natto

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