Natto's origin legend attributes it to Minamoto no Yoshiie (11th century CE) who accidentally fermented soybeans wrapped in straw during a military campaign; more likely developed from Buddhist temple food traditions of fermented soybeans; Mito, Ibaraki Prefecture, is the 'capital of natto' with the Mito natto brand holding protected regional status; the rice straw wrapping (containing natural Bacillus subtilis populations) was the traditional inoculation method before standardised Bacillus cultures
Natto (納豆 — fermented soybeans with Bacillus subtilis) is Japan's most divisive food and one of the world's most complete nutritional packages — small soybeans wrapped in rice straw that have been inoculated with Bacillus subtilis var. natto, fermented at 40°C for 24 hours, developing a characteristic ammonia-pungent aroma, intensely sticky stringy texture (from poly-glutamic acid chains produced by the bacteria), and profound earthy-savoury flavour. The flavour is far more complex than any other fermented soybean product: Bacillus subtilis produces protease enzymes that break down soy protein into amino acids including glutamate (umami), free amino acids with distinct flavours, and volatile compounds including pyrazines (roasty), disulfides (pungent), and diacetyl (buttery). Nutritional density: natto is the world's richest food source of vitamin K2 (MK-7 form), contains all essential amino acids in high concentration, and has active nattokinase enzyme (a fibrinolytic enzyme claimed to reduce cardiovascular risk). Cultural geography: natto is primarily a Kanto and Tohoku food — the further west you travel in Japan, the less natto appears on breakfast menus; Kansai diners frequently cite natto as unacceptable.
The poly-glutamic acid strings of natto are literally made of glutamate molecules — the sticky strands are concentrated umami; the amino acid breakdown products include free glutamate at 100+ times higher concentration than the raw soybean; the Maillard-like pyrazine compounds from Bacillus metabolism add complexity; together these create a flavour that is simultaneously more pungent and more deeply savoury than any other soybean preparation
Stir before serving is essential — more stirring (100+ times with chopsticks) produces more even glutamic acid distribution and the characteristic stringy foam; serve at room temperature not cold (cold suppresses both flavour and strand formation); the standard condiment is soy sauce and hot mustard (karashi), never wasabi; natto requires sticky short-grain rice to make the strands manageable; the ammoniacal smell indicates active Bacillus activity — a sign of freshness, not spoilage.
The 'natto connoisseur' technique: stir 200+ times with chopsticks until the strings form a thick white foam — this aeration softens the flavour and creates the ultimate strand texture; add karashi (hot mustard) before stirring for even distribution; standard breakfast natto: one 40g pack (single serving), stir with mustard and soy, pour over rice, mix at table; natto is incorporated into many Japanese dishes: natto-maki sushi roll (thin roll with natto filling), natto spaghetti (a 1990s popular dish — natto + soy + butter + spaghetti), natto tempura, and natto miso soup.
Eating natto cold (suppresses flavour and strand development); not stirring thoroughly (uneven flavour distribution); using natto past peak freshness (2 weeks from production) when ammonia overwhelms other flavours; pairing with delicate food — the aggressive flavour overwhelms anything adjacent.
Hachisu, Nancy Singleton — Japanese Farm Food; Shockey, Kirsten and Christopher — Miso, Tempeh, Natto