Making Japanese Sake 日本酒が出来るまで
It is ideal to use only the inner core of the rice grains, which allows for the creation of a purer sake. Polishing down the grain increases the amount of raw rice needed for production, and requires extra time and energy.
Because of this, a low polishing ratio (how much of the rice is left after grinding off the outside part) often indicates a quality sake.
The differentiation between the sakes made with rice and koji is the amount of milling the rice has undergone before brewing. They include three groups: Junmai (polished to at least 70% of the original size of the grains), Junmai-Ginjo (polished to at least 60%), and Junmai-Daiginjo (polished to at least 50%).