Filtration is one of the finishing touches to sake

Roughly speaking, the process of sake brewing involves steaming rice, making rice koji, making yeast starter, and fermenting, after which the resulting mash is pressed to produce sake. But it's not finished yet. Depending on the type of sake, there are various "finishing" steps before bottling, such as removing sediment, filtering, pasteurizing, storing in tanks, and adding water. Today, we'll take a closer look at one of these, filtering.

"Filtration" is the process of removing foreign matter from liquids or gases. In the case of sake, it is done to remove components that cause coloring and unpleasant flavors. Freshly pressed sake is cloudy, so it is left in a tank for several days to allow the solids (sediment) to settle. This is called "sedimentation." After sedimentation, sake still contains fine particles and has a slight yellowish color, so it needs to be filtered to make it clear.

New methods of filtration also appear

Generally, powdered activated charcoal is used for filtration. One theory is that it began in the Edo period, when a servant who was unhappy with the way his master treated him threw ashes into a wooden vat of sake in revenge, which removed the cloudiness from the sake and gave it a cleaner taste. Nowadays, activated charcoal for brewing is added to the sake that has been decanted, and the countless tiny pores on the surface of the charcoal absorb impurities, and the sake is then passed through a filter equipped with a filter. However, care must be taken not to overdo the charcoal filtration, as it can remove the flavor and aroma of the sake and can also cause an unpleasant charcoal smell.

In addition to this type of charcoal filtration, filtration using an SF filter has recently appeared. SF filters are filters made of a bundle of hollow fibers like straws, and are now being used in many sake breweries because they can remove yeast and other bacteria that cause deterioration.

Reasons for and against filtration

Unfiltered sake, especially unfiltered unpasteurized sake, is becoming more common these days. Originally, it was only available at the sake brewery, but with improvements in quality and distribution management, it is now easily available at liquor stores. As it is unfiltered, you can enjoy the flavor of the sake as it was pressed, but on the other hand, it is prone to deterioration, so care must be taken. In that respect, filtered sake is easier to maintain a stable quality.

Filtered sake has a clear, well-balanced taste and goes perfectly with refreshing Japanese food. Unfiltered sake is slightly golden in color, has a strong umami flavor, and is full of personality. It goes well with rich dishes and Western food. If you're not sure whether to have filtered or unfiltered sake today, why not choose one that matches your food?

Writer/Sake Master Eriko Fujita
Expand your world to a sake specialty store in Osaka and encounter a variety of sake and sake breweries. Favorite sakes are Akishika, Ohgi, and others.
Other than drinking, my hobbies include collecting minerals and raising swallowtail butterflies.