Rice bran (komenuka)

Rice bran (komenuka) is a by-product made up of the outer layers and germ that are removed when brown rice is polished. Depending on the rice polishing ratio, it is classified into types such as red bran (akanuka), medium bran (chunuka), white bran (shironuka), and special-grade bran (tokujo nuka) or special white bran (toku shironuka). In general, the higher the rice polishing ratio, the more nutritious the bran. Special-grade bran in particular is rich in components beneficial to health, and is sometimes used in foods and health supplements. Rice bran is also described as playing an important role in koji making. When tane-koji (koji starter spores) is sprinkled over steamed rice and the koji mold multiplies, the enzymes it produces break down the rice and convert starch into glucose. This change supplies an energy source that yeast can use and allows fermentation to proceed, which is why rice bran is regarded as very important in sake brewing.