Miso is a traditional Japanese fermented seasoning made by mixing boiled soybeans with salt and koji (a fermentation starter). Depending on the type of koji used, miso is categorized into kome miso (rice koji), mugi miso (barley koji), and mame miso (soybean koji). When two or more types of miso are blended, or multiple types of koji are used, the result is called awase miso (blended miso).
Miso is also classified by color into red miso (akamiso) and white miso (shiromiso), which differ based on how the soybeans are cooked, the amount of koji, the frequency of stirring, and the fermentation time. Red miso is characterized by its dark color and higher salt content due to longer fermentation. White miso, on the other hand, uses more koji and has a shorter fermentation time, resulting in a sweeter flavor. The commonly available yellowish miso is somewhere between red and white miso.