06 Pressing | Filtering
When the fermentation is complete, the main mash(moromi) is filtered with cloth and the undissolved rice and yeast removed, leaving the new sake. This process may be done by placing the moromi in a cloth bag and suing a machine to apply pressure from above or by using a horizontal machine similar to a beer mash filter press.
With the initial filtration, some turbidity remains. If the liquid is left to stand at a low temperature, this precipitates out as sediment and the clear part is transferred to another tank.
It is then filtered to produce a clear liquid. However, sake that has been filtered to make it clear may lose its transparency during storage. This is due to changes in the proteins dissolved in the sake, causing them to become insoluble. The use of persimmon tannin or colloidal silica is approved to removing the proteins that cause this cloudy appearance.
Use of active charcoal is also approved for de-coloring, flavor adjustment and control of the aging process.