Shinkudo (bottle vacuum level)

Shinkudo (vacuum level) is an index of the pressure inside a bottle of sake, used to measure the degree of reduced pressure within the bottle. It is measured with a vacuum gauge and is an important indicator when judging bottle quality, the tightness of the crown cap seal, and whether the bottle has been capped properly. In general, for a 1.8-liter bottle, a vacuum level in the range of 40 to 60 is considered good. Because a proper vacuum level contributes greatly to how well the sake is stored and how well its quality is maintained, it is an important factor for producers.