Rice polishing machine (seimaiki)

A rice polishing machine (seimaiki) is a machine used to mill rice, and it plays an important role in the sake brewing process. Unlike the kind used in ordinary households, the machines used for sake brewing are dedicated vertical rice polishers. In these machines the rotating shaft is vertical, and the surface of the brown rice is carefully ground away with special grinding rolls called kongo rolls (金剛ロール). During milling, the rice is passed through the machine many times, removing a little at a time, until it reaches the target rice polishing ratio (an index determined by how much of the rice's outer layer is ground away). This milling exposes the starch contained in the center of the grain and prepares the rice in the ideal condition for sake brewing. The lower the rice polishing ratio, the higher the purity of the rice, making it possible to produce sake with a more delicate and clean flavor.