Japan — Mito, Ibaraki Prefecture is the documented historical center; legend attributes invention to the 11th century military general Minamoto no Yoshiie; industrial natto production developed in Meiji era
Natto (納豆) — fermented soybeans produced through Bacillus subtilis var. natto fermentation — is one of Japan's most nutritionally dense, culturally divisive, and regionally specific foods. While consumed across Japan, Ibaraki Prefecture (particularly Mito City) is the historic natto capital, and its relationship with the fermented food is deeply cultural. Beyond the standard breakfast presentation (natto on rice with soy, karashi, and negi), premium natto in Ibaraki is used in: hikiwari natto (coarsely crushed natto) in miso soup; natto as a ramen topping; natto-jiru (natto dissolved in miso soup); natto tempura (challenging but remarkable); natto pasta; and in professional kitchens, fermented natto liquid as an umami-active sauce base. The controversial sticky, stringy texture and pungent aroma (from pyrazines and other fermentation byproducts) are features requiring cultural framing to appreciate.
Pungent, deeply savoury, slightly ammoniated with earthy fermented depth; the flavour is acquired but once acquired is irreplaceable as an umami source; the sticky texture is integral to the experience
Stirring natto vigorously before eating is standard practice — the strings become longer and the flavour develops as the strings form. Conventionally 30–50 stirs with chopsticks is recommended; some natto aficionados stir over 300 times, claiming the flavour becomes more mellow and integrated. Natto's B. subtilis bacteria remain alive in the package and continue fermenting — consume by the use-by date for optimal flavour (before it becomes overly ammoniated). The enzymes in natto (nattokinase) are considered beneficial for cardiovascular health — this has contributed to natto's health food status.
The natto paste approach for non-traditionalists: blend natto with a small amount of mirin and soy sauce to create a paste that is spread on toast or used as a ramen flavour base — the texture becomes manageable and the fermented umami is spectacular. Hikiwari natto (cracked/halved beans) has a more uniform texture and less dramatic string than whole-bean natto — a better entry point for first-timers. Premium Mito natto from Ibaraki uses carefully selected large soybeans (okura natto) for a bean that holds its shape while developing a tender, creamy interior.
Adding soy sauce before stirring — add the soy sauce after the initial stirring to prevent premature softening of the beans. Serving warm natto when cold or room temperature is preferred for most applications (heat kills the bacteria and changes the texture). Consuming natto immediately after refrigerating — allow 5 minutes at room temperature for the flavour to develop. Using low-quality natto — premium natto from small Ibaraki producers uses specific soybean varieties and natto strain selections that differ dramatically from mass-produced varieties.
Hosking, Richard — A Dictionary of Japanese Food; Ibaraki Prefecture food documentation; natto producer documentation