Natto

Natto is a traditional Japanese food made by fermenting cooked soybeans with a specific bacterial culture, which produces a distinctive sticky, stringy texture when the beans are stirred, along with a strong, pungent aroma that is quite different from most vegetable or dairy ferments. It is typically fermented for about a day at a warm, fairly precise temperature.

Making natto at home usually involves cooking soybeans until soft, inoculating them with a natto starter culture, then holding them at a steady warm temperature, often using a dedicated incubator or a yogurt maker repurposed for the job, since the bacteria involved need consistent warmth to develop properly. Humidity and temperature control tend to matter more for natto than for many vegetable ferments.

New fermenters are sometimes put off by natto's smell and texture, assuming something has gone wrong, when in fact both are characteristic of a successful batch. As with any fermented food, checking for genuinely unusual signs, such as unexpected colors or a smell that seems more like rot than the food's normal aroma, is a better guide than judging it against foods that are supposed to smell milder.