Vinowa - Sake

BREWING SAKE

A general description of sake brewing looks something like this. Rice is washed and steam-cooked. This is then mixed with yeast and koji (rice cultivated with a mold). The whole mix is then allowed to ferment, with more rice, koji, and water added in three batches over four days. This fermentation, which occurs in a large tank, is called “shikomi”. The quality of the rice, the degree to which the koji mold has developed, temperature variations, and other factors are different for each “shikomi”.

This “Shikomi” then completes within 18 to 32 days, after which it is pressed, filtered and blended (non-blended sake is called “ki-ippon”). Now let us look at the main steps and each processes a bit more closely.

Rice Milling
A special kind of large grained rice called “Sakamai” is used for making premium sake. Costing 4 to 10 times as much as table rice, it has a higher starch content with little protein and fat. Most of the starch is in the centre of the grain, while the fats and proteins are around the outside. It is this starchy white heart of the grain that sake brewers use. First, the rice is polished. The outer surface is literally milled off, leaving the starch rich middle exposed. Depending on the quality of the sake, the grain may be reduced to less than half its original size. This is not as simple as it might sound, since it must be done gently so as not to generate too much heat (which adversely affects water absorption by milled grain) or not to crack the rice kernels (which is not good for the fermentation process).

Washing and Soaking
Next, the white powder (called nuka) left on the rice after polishing is washed away, as this makes a significant difference in the final quality of the steamed rice. Following that, it is soaked to attain a certain water content deemed optimum for steaming that particular rice. The degree to which the rice has been milled in the previous step determines what its pre-steaming water content should be. The more a rice has been polished, the faster it absorbs water and the shorter the soaking time. Often it is done for as little as a minute, or as long as a whole night.

Steaming
Next the rice is steamed. Note this is different from the way table rice is prepared. It is not mixed with water and brought to a boil; rather, steam is brought up through the bottom of the steaming vat (called a koshiki) to work its way through the rice. This gives a firmer consistency and slightly harder outside surface and softer center. Generally, a batch of steamed rice is cooled down and divided up, with some going to have mold spores sprinkled over it to develop koji, and some going directly to the fermentation vat.

Koji Making (Seigiku)
This is the heart of the entire brewing process, as Koji is the mould which converts the starch in the rice to fermentable sugar. Koji mould in the form of a dark, fine powder is sprinkled on steamed rice that has been cooled. It is then taken to a “kojimuro” a wood-lined room where the humidity and temperature are kept high. Over the next 36 to 45 hours, the koji is mixed and re-arranged constantly under the close monitoring. The koji rice looks slightly frosted, and smells faintly of sweet chestnuts. Koji is used at least four times throughout the process, and is always made fresh and used immediately. Therefore, any one “shikomi” goes through the "heart of the process" at least four times.

Yeast Starter (Shubo or Moto)
A yeast starter, or seed mash, is first created. This is done by mixing finished koji and plain steamed white rice, water and a concentration of pure yeast cells. Over the next two weeks, (typically) a concentration of yeast cells that can reach 100 million cells in one teaspoon is developed. The koji and yeast simultaneously work together to convert the rice starch into glucose and the glucose into alcohol. This parallel combined fermentation is unique to sake production.

The Mash (Moromi)
When the moto is matured, it is transferred to a larger tank. Then the butches of water, plain steamed rice, koji and water are added in three successive stages over four days, roughly doubling the size of the batch each time. This is the main mash, moromi, which ferments over the next 18 to 32 days, whose temperature and other factors are measured and adjusted to create precisely the flavor profile being sought.

Pressing (joso)
When everything is just right, the sake is pressed. Through one of several methods, the white lees (called kasu) and unfermented solids are pressed away, and the clear sake runs off. This is most often done by machine, although the older methods involving putting the moromi in canvas bags and squeezing the fresh sake out, or letting the sake drip out of the bags, are still used.

Filtration (Roka)
After sitting for a few days to let more solids settle out, the sake is filtered and resulting in fresh sake.

Pasteurization
Most sake is then pasteurized once. This is done by heating it quickly by passing it through a pipe immersed in hot water. This process kills off bacteria and deactivates enzymes that would likely adverse flavor and color later on. Sake that is not pasteurized is called namazake, and maintains a certain freshness of flavor, although it must be kept refrigerated to protect it.

Aging
Finally, most sake is left to age about six months, rounding out the flavor, before shipping. Before shipping it is mixed with a bit of pure water to bring the near 20 percent alcohol down to 16 percent or so, and blended to ensure consistency. Also, it is usually pasteurized a second time at this stage. The new trend for ageing is coming about last 10 years or so, however in limited quantity due to its tax regime in Japan that the sake which is brewed but not sold are levied till they are sold.