The content below was provided by Sake One. For more details on Sake One products go to http://www.sakeone.com
Saké is brewed from rice (no other grain) with water, yeast and koji being the only other ingredients. What makes it very unique in the realm of beverage are two things:
Koji: Aspergillus Oryzae – a mold that is applied to the rice grains.
Multiple Parallel Fermentation: Saccharification and fermentation taking place at the same time.
Rice:
Rice, the foundation of saké, comes in many varieties but, like grapes are to wine, only a few are good for brewing saké. Varieties have been cultivated for centuries and today there are about a dozen that are highlighted for saké brewing due to their hardness (impacts milling), aroma and flavor. Regional varieties of rice differ and are the source of local pride, allowing a sense of terroir. It is important to know the variety of rice used in the saké you drink but not critical. Back labels & brochures are sources of rice clarity. Names that you will most commonly see include Yamadanishiki, Gohyakumangoku, Akita Komachi, Miyamanishiki, etc.
Polishing – aka Milling
Once rice is harvested and the hull removed, it is up to the brewer to define how much of the grain they want polished off. It is here that saké quality is measured, by how much of the grain is kept.
Specialty millers manage the polishing process to the exacting standards of the brewer. A key goal is to minimize cracking and breakage of the grain which will negatively impact the Koji process by allowing Koji mold to grow to quickly into the grain.
Milling/Polishing in another term: Seimaibuai. The Japanese term shows up frequently today so don’t be caught off guard. Seimaibuai = Milling/Polishing.
Washing & Steaming
Once the rice is polished it must be washed to remove all residual flour. Next, the rice gets a good soak. The length of soaking time is defined by the rice strain and water saturation goals. A stopwatch is used to be precise in timing down to the millisecond. Such precision is necessary to ensure to maximized koji growth and penetration into the grain.
The final step in prepping rice for either Koji or straight to brewing, is to steam. This is done at about 195° Celsius in either a belt steamer or kettle. If in a kettle, the rice is separated from the steel with thick cotton cloths and carefully layered to allow the steam to find its own path allowing for even steaming. A belt steamer moves the rice through a flat pressure steamer and provides even, steady steam for enhanced quality.
Once upon a time in a not too distant past, a critical step in making saké was to chew the rice and spit it into a bucket. This gathered enzymes that aided in breaking down the grain. Thankfully, that step is no longer needed but the process of making koji is still considered the most sacred step in production.
Enter Koji (aspergillus oryzae), a mold that grows on the steamed, but cooled, rice and in doing so digests it with enzymes that convert the starch into sugars. Koji spores are applied to the steamed rice which is then carefully managed with temperature and humidity controls. Slight shifts in temperature, length of time, or humidity can mean the difference between perfectly fragrant and rich yeast food and old smelly sneakers. Koji also adds a good deal of flavor to sake.
Yeast
Like beer and wine, saké needs yeast to ferment. It is to create food for the yeast that rice is polished, washed, steamed and covered with Koji. In doing this we convert the hard grain into soft, sweet kernels, perfect for consumption by yeast. There are about 14 commercial yeast strains available to brewers. Each has it’s own aroma and flavor profile and interacts with the rice in different ways. Yeast is selected for the desired end result.
Some of the older brewers in Japan also use proprietary yeast that has been cultivated at their kura for decades or centuries. This provides the kura with uniqueness and when combined with local rice and water provides a definition of terroir for saké.
Water
It might seem obvious that water is a necessary ingredient since rice has no juice to press out, but it is often overlooked. Sake is about 80% water. Ideal brewing water is low in minerals with little to no iron. Iron will cause saké to darken and create undesirable aromas and flavors. It is also known to hasten the aging process.
Manganese interacts with light causing saké to become discolored and dampen the overall look and character. Good elements in brewing water include potassium, magnesium and phosphoric acid. These aid propagation of yeast and development of Koji. The flavor of the water is also very important as the water used in brewing is also used in diluting sake. A majority of all sake is diluted to reduce alcohol and mellow flavors.
Moto & Brewing
The first place that steamed rice,Koji rice, yeast and water come together is the moto tank (first tank). Here, yeast begins to feed on the sugars and starches and the natural processes begin to do their thing. After a few days, the moto is added to a larger brewing tank where more Koji rice, steamed rice and water is added as desired.
The sakémaster’s role now is to carefully manage brewing temperature, food and time. A brew that is too warm will go to quickly, one that is too cool will be slow and could stop short of desired alcohol levels. Manipulating temp and time will help define flavor and body in the finished saké.
The Magic Of Multiple Parallel Fermentation
In beer or winemaking, saccharification and fermentation are sequential, but in sake, multiple steps take place at the same time – Multiple & Parallel. This is because the koji rice is in the fermenter at the same time as the yeast, both are functioning simultaneously. What is magical is that the enzymes are slowly releasing sugar to the yeast, which is in turn slowly eating the sugar. This natural management process allows the yeast to digest sugars over time instead of rapidly, therefore allowing alcohol levels to be much higher than beer or wine. Saké actually has the highest fermented alcohol level of all fermented beverages.
Pressing
Unless the saké is to be “Nigori,” the remnants of brewing need to be removed.
As noted, real old school pressing is simply allowing it to free run from a hanging cloth sack. This is called “Shizuku,” or free drip.
“Funashibori” is another old traditional style using a wood box filled with sacks of saké mash that are pressed with weight. There are three phases of this style. The first being “Arabashiri,” where saké flows freely from the sacks. “Nakadori,” is drawn from the first press. And, “Seme” is the last of the saké drawn out by hard squeezing to get the last drop.
The Yabuta press is a modern machine that pumps the saké through screens that catch the sediment and clarify the saké. About 90% of all saké is pressed this way. Also known as “Asakuki.”
Filtration
For saké, filtration is very much like the fining process in winemaking. The heavy bits have been removed leaving a fairly clear liquid but retaining small bits that can cause the liquid to be hazy. To remove this, an optional charcoal filtration is implemented. This stage is referred to as “Orisagé,” and is used to strip out particulates and coagulated proteins. Filtration may be done multiple times depending on the need or desired impact. This process can also remove desirable flavors so it’s use is managed carefully.
Muroka is a style of saké that has not been filtered. It is often hazy, yellowish and to old ideals it less than perfect. To Western standards it may taste richer and fruitier compared to it’s filtered version.
Pasteurization
Long before Louis Pasteur “invented” pasteurization, Japanese saké brewers were heat treating their brews to stabilize them and make sure they would not go bad too quickly.
Today, saké is typically pasteurized twice, once after filtration and once at bottling. Some high-end saké are bottled between pasteurizations and then pasteurized in bottle. This step allows saké to be stored for longer periods of time. Without this process it would quickly change in flavor and density.