Koshiki (steaming vat)

A koshiki is a tool used in sake brewing to steam the raw rice. It is generally shaped like a tub, with a hole in the bottom (the koshiki hole, 甑穴) through which steam rises and steams the rice evenly. Traditionally koshiki were made of cedar, but lightweight, durable koshiki made of aluminum or stainless steel are now the mainstream. Many breweries today also use conveyor-type continuous rice steamers, which make the steaming process more efficient. Steaming in a koshiki gelatinizes the starch in the rice, which plays an important role in sake brewing.