natto a Japanese fermented product made of soya beans, unusual in that it is fermented by bacteria (Bacillus subtilis) not by the moulds used for Indonesian tempe and other fermented soya bean products.
The bacteria give the beans a whitish coating and a flavour and texture which not all Japanese appreciate and which most other people find disconcerting. The flavour is strong, musty, and faintly ammoniac, and the bacteria develop on the beans a sticky slime which forms ‘strings’; the longer these are, the better the natto, according to those who like the product.