Filter aid (rokajozai)

A filter aid (rokajozai) is a substance used in the filtration step of sake production. Its main roles are to prevent the filter medium from clogging and to capture fine particles effectively, which makes it possible to obtain sake with a high degree of clarity. Commonly used filter aids include diatomaceous earth and pulp fibers, which are often coated onto the surface of the filter medium to improve filtration efficiency. Choosing and using the right filter aid is a very important factor in maintaining the quality of sake.