In Korean culture, we eat fermented soybean products every day, such as soy sauce, soybean paste (Doenjang),and red pepper paste (Gochujang). An important part of making these fermented soybeans is the rice straw. My grandmother always says, “Save the rice straw, it is useful for something.”
Bricks of dried fermented soybeans are tied in rice straw and hung where there is good air circulation. The rice straw has Bacillus subtilis, a good bacteria, which promotes the fermentation process. Over time the soybeans absorb the bacteria in the rice straw. The bacteria is important because it creates a sticky substance which gives the soybeans their unique aroma and taste.
In Korean these fermented soybeans are called Meju. Meju is the key ingredient in making soy sauce.
A soybean used in Japanese cooking called Natto is also wrapped in rice straw. It becomes very sticky and pungent in its fermented form. Just like the Meju, Nattō needs the correct temperature, humidity and circulation to be its best.
In the Edo Period (1615-1868), there were " Nattō vendors" who walked around town selling their fermented soybeans during the fall and winter months when the bacterium grew readily. Today, Japanese consumers have access to Nattō year round. Nattō is a traditional food eaten at Japanese breakfast tables together with miso soup, fish, and rice.