Just as water, barley, malt and hops can create myriad varieties of beer, so can water, soy and natto bacillus generate a lot of different types of natto. By adding salt or other flavorings, or additional steps to its processing, Japan has generated many regional styles and preparations for natto.
There are two main types of Japanese natto: itohiki-natto (unsalted, sticky natto) and daitokuji natto (salted natto, also known as “hama-natto” or “temple natto”). The former is much more common and is the food most widely understood as “natto”.
There are over 400 varieties of soybean cultivated today. Most of the soybeans used in Japanese natto production are grown in the United States, Canada and China, with only a very small percentage grown in Japan. Natto typically uses small soybeans, though larger beans, red or black soybeans and chopped beans (“hikiwari”) are all relatively common in commercially-produced natto. Black and red soybeans may have a slightly different taste and texture, and the size of the beans affects their texture and the Which is best is largely a matter of preference. Soybeans are sized according to the following scale:
Large: larger than 7.9 mm in diameter
Medium: 7.3 mm – 7.9 mm
Small: 5.5 mm – 7.3 mm
Extra-small: 4.9 mm – 5.5 mm
The largest type of soybean in Japan is Tanbaguro, with each bean weighing 0.7 gram. The smallest is the Nattoshoryo, which is especially prized for natto production. Each Nattoshoryo soybean weighs less than 0.10 of a gram.
Three types of natto starter are widely used: miyagino, naruse, and takahashi. There are many other starters used by small producers, but one of these three is found in most commercial natto. Recent research into starter development has focused on maximizing the desirable, or at least most marketable, aspects of natto. Some starters produce natto with more of a savory umami taste, but less of the slimy viscosity so many people find offputting. On the other hand, some people find the stringy, viscous properties of natto and its characteristic pungent smell to be its main attractions.
Sticky natto must typically be eaten within a few days, before it ferments to the point where the ammonia content becomes too high. Natto can also be preserved for long periods by salting or drying; the fresh natto is sprinkled with salt, stored for about three months, and then dried. Some natto is dried to the point where it is still a paste similar to miso. Other salted natto may be dried to the point where it can be ground into a topping or into flour, or it may also be eaten as a snack.
Natto varieties and preparations from across Japan include:
Salty “temple natto” made with black soybeans, a specialty of Kyoto. Sometimes served as an accompaniment to the traditional Tea Ceremony.
A type of itohiki (sticky) natto, goto natto is made with cracked (hikiwari) natto mixed with malted rice. A specialty of Yonezawa in Yamagata prefecture.
Salted “temple natto” which resembles whole-bean miso, a specialty of the city of Hamamatsu. Traditionally made in the temples of Daifukuji and Horinji. A similar preparation is Daitokuji natto.
Natto prepared by burial in the ground, a method used in Kumamoto Prefecture on Kyushu.
Natto made with chopped soybeans.
A dried natto, commonly eaten as a snack or as an ingredient in rice toppings. Sometimes mixed with spicy togarashi pepper, traditional on the southern island of Kyushu.
A type of temple natto (tera natto), it is dark, salty preparation of natto that is sun-dried for long periods, making it suitable for long storage. Only a handful of monks retain the tradition of making this type of natto.
Natto made with whole beans, as opposed to cracked or crushed beans.
Natto made from very small soybeans, a specialty of Ibaragi Prefecture.
A natto preparation from Fukushima prefecture, made by rolling natto in cotton bags inside a reed mat, then fermenting it inside a warm compost heap.
Recently developed “low-odor” versions of natto produced with special starters, sometimes featuring reduced stringiness as well. Popular in Japan and elsewhere among those who enjoy natto, but find the smell and texture of traditional natto overwhelming.
Omugi natto (Barley natto)
Barley is sometimes added to soybeans during natto production. This variety is said to be more viscous than natto made only with soy. This type is not widely available outside of Japan.
A broad term for dry, salty preparations of natto, including varieties of tera (temple) natto and goto natto.
A mixture of white radish (soboro) and natto. The dried radish and natto are preserved in brine and can be stored long-term. This is a specialty of the Ibaraki Prefecture in central Japan.
Dried, salty natto, also known as “tera natto”, it is salty and typically dark in color. It was allegedly introduced to Japan by Buddhist priests returning from study in China sometime during the 15th century. Temple natto is said to be similar to red miso in taste.
See “temple natto”.
A salty “temple natto” made in the temple of Tenryuji.
A natto dish local to Chiba prefecture, made with daikon, persimmons, salt and koji.
A variety of “barrel natto” made in Yamagata Prefecture (northeastern Japan), made with salt and koji. It is brewed in a large barrel and was traditionally made during the winter months.