The question most people ask me about sake is whether it’s a wine or a beer.  The fact is sake is neither, the brewing process is unique and sake is a beverage in its own class, neither beer, wine, nor distilled spirit.  Wine is created through the fermentation of grapes where the sugar in the juice from the grapes is converted by yeast to alcohol.  Beer is a two-step process where first the grain used to create the beer is malted.  The malting process creates enzymes which then in turn convert the starch in the grain into sugars.  At that point yeast is added and fermentation process begins.

Sake is made from rice but the enzymes that convert the starch to sugar are on the outside of the rice.  The outer shell of sake rice is removed before being introduced to the brewing process so sake brewers use a special kind of mold called Koji-kin to convert the starch in rice to sugar.  The thing that makes the sake process unique is that the process of converting starches to sugar occurs at the same time as the fermentation.  No other alcoholic beverage uses quite the same process as sake.

The rice used to make sake is called Sakamai and is very different than the rice that we eat.  Sakamai rice grains are 25% larger than table rice and are much more challenging and time intensive to grow.  The rice stalks grow very tall and due to the large size of the grains are prone to tip over and fall into the water in the rice paddy during storms which will ruin them.  This height means the rice must be harvested by hand rather than by machine.  Sakamai is also more susceptible to insecticides, and requires optimal growing conditions.  As a result of all these factors sake rice is three times more expensive than table rice.

The starches for sake rice are concentrated in the center of the kernel.  The proteins, minerals, and fats which can adversely affect the flavor of the sake are distributed on the outside.  For that reason sake rice is milled to remove the outer shell before the brewing process begins.  The milling of the rice must be done slowly and carefully as if it’s done too quickly, the rice will heat up which will adversely affect the flavor of the finished product.

The more of the outside shell that is milled away, the more pure the sake will be.  Premium sake is rated by different classes and a major determinant of class is the degree by which the sake is milled.  Junmai Dai Ginjo which is the highest grade of sake is made with rice that has had up to 65% of the rice grain removed.  The powder that is milled away is not wasted but is reused for livestock feed and consumer foods such as crackers.

After the rice has been polished it is washed and soaked.  The washing removes any remaining powder from the milling.  Soaking allows the rice to absorb water which is controlled very carefully in premium sake.  The amount of water absorbed by the rice will greatly affect how the rice dissolves during the fermentation process.

Once the rice has finished soaking it is steamed.  The rice must be steamed to a point where it is neither too mushy nor too firm.  After the rice is steamed it is spread out on large pieces of cloth to cool.

The next phase is a crucial one where some the rice (usually around 30%) is set aside and mixed with a special mold called Koji-kin.  The mold is sprinkled onto the rice and mixed over the course of two days.  The resulting mix is called Koji and it takes many years for a sake brewer to understand this part of the process.  Sake brewers typically do not sleep much if at all when the Koji is being made.

When the Koji is complete it is mixed with yeast and a small amount of lactic acid to protect against bacteria.  The yeast feeds off the sugars created by the Koji to begin the fermentation process.  Gradually more rice is added over a 2-3 week period to create what’s called Moto.

The Moto is then combined in much larger vats with the remainder of the rice and lots of water.  The rice and water are added in phases over a four-day period to create what’s called Moromi.  The Moromi is then allowed to ferment for 18 to 32 days.  The brewer must take care to stop the fermentation process at the proper time as too long or too little fermentation will dramatically impact the sake flavor.

The next phase is pressing.  Pressing has changed radically over the years and is automated in many breweries today.  In olden times the Moromi was put in cloth bags which were then put into presses and squeezed to eject the liquid which was in fact the sake.  Modern breweries use an accordion-like machine to press the sake but there exist breweries today that still use the manual method and many people find that the flavor is noticeably better.  Sake typically sits for 10 days after pressing to allow sediments to settle and chemical processes to finish.

The next step is filtering where the bits of rice are removed from the sake.  After this the sake is pasteurized by heating it to 150 degrees Fahrenheit.

Finally, water is added to the sake to bring its alcohol content down from its natural amount of 20% to around 16%.  Most sakes then age for 3-6 months before bottling.

This is an extremely simplistic overview of the brewing process.  Sake has been being made for thousands of years and the evolution of the brewing process is a complex and fascinating topic.  There are numerous web sites and resources that go into much more detail about the sake brewing process including:

http://www.sake-world.com/html/brewing-process.html
http://en.wikipedia.org/wiki/Sake

I hope this post was informative.  Next I’ll be reviewing a delightful little sake that I picked up locally and can’t wait to open.  Stay tuned.

Yama