If you've ever wondered how sake is made, here's a basic rundown of how it's done.
Premium grade brown rice is selected to be milled. Milling removes the lipids and proteins on the outside of the rice grain. The degree to which the rice is milled down, which could range anywhere from 30% - 70%, determines the grade of sake that will be produced. Please refer to the Grades of Sake page for more information.
Washing and Soaking
The rice is washed to remove any dust or particles and then placed in rice washing bags which are then soaked in cold water to attain the right consistency and water content.
The rice is cooked in the steamer under pressure which allows for the rice to have a tender center and firm outer coating. The steamer is usually covered with a cloth. It is important not to overcook, undercook the rice.
Once, the rice has cooled, Kojikin, or mold spores, are added to the cooked rice to produce Koji. It usually takes about 48 hours to complete the process.
As soon as the Koji is ready, the koji, water and yeast starter (moto/shubo) are added to steamed rice to start the fermentation process. The purpose of the moto/shubo is to control harmful fungus and bacteria with lactic acid, and to sustain the fermentation process. The mold in the koji convert the starch in the rice to sugars. The sugar feeds the yeast, which is what produces the alcohol.
Pressing the sake separates the liquid from the rice particulate which is what makes the sake cloudy. The sake is poured into cloth bags and then placed in a pressing machine that uses pressure to squeeze out the sake. Another method is to use a fune which involves placing a weight on the bags and using gravity to press the sake.
Some breweries choose to use charcoal to filter the sake and remove more of the rough flavor and any color.
Breweries have the option of pasteurizing the sake to stop the fermentation process. This kills the yeasts and preserves the shelf life of the sake.
The sake is then bottled, or stored in tanks for aging for about 6 months or so.
Sometimes sake is diluted, re-filtered or pasteurized again to attain the flavor the brew master is trying to achieve.
The sake is then bottled and ready to be enjoyed!