Premium Sake is crafted solely from Rice, water, yeast and Koji – all details about ingredients here.
The brewing process: Similar to beer – just very different…
Like beer, Sake is made in a two-step process involving saccarification (converting starch into sugar) and fermentation (using yeast to convert sugar to alcohol). Unlike beer, however, these two processes occur not in two distinct steps but simultaneously!
The saccarification is started by adding ‘Koji’ (a special mold that converts rice starch into sugar) to a small part of the rice; shortly after, the actual fermentation is started by mixing this Koji rice with additional fresh rice, water and yeast – but during the ensuing Fermentation, the saccarification process continues and propagates throughout all of the rice in the batch. This ‘multiple and parallel’ fermentation process is extremely complex and volatile, places high demands on the skills of the ‘Toji’ (brewmaster), and results in the highest alcohol content of any non-distilled alcoholic beverage!
Brewing Sake – The key steps
Polish – remove the outer layers of the rice corn
Steam - steam the polished rice
Koji – start the saccarification process by adding the special mold ‘Koji’
Moto – create the Sake-starter
Fermentation - add more raw material
Filtration - separate the Sake from solid particles
Pasteurizing - conserve Sake with a mild pasteurization!
Rice is the central and most important ingredient of Sake – for premium grade Sake only very special breeds of ‘Sake Rice’ that have abundant starch in the core (e.g., YamadaNishiki or Bizenomachi) are used. The outer layers of each rice corn, which contain unwanted, taste distorting elements such as wild amino acids, are then removed, so that we only use the pure inner core* of the rice for the actual brewing process!
For the highest quality Junmai DaiGinjo – our Limited Edition – at least 50% of the rice corn needs to be milled away; the next quality level, Junmai Ginjo, requires that at least 40% of the rice is polished away – our Premium Select is part of this quality level with a polishing rate* of 45%. See here for more information on Sake quality levels.
Polishing the rice allows us to literally start with the purest of raw materials and create one of the most refined and, well, ‘pure’, of all alcoholic drinks!
* Note: the milling residue is usually not thrown away but used in the cosmetics industry (e.g., for skin cremes) or as animal feed.
* Note: in Japan, the polishing rate is usually expressed the other way around, i.e., if 45% is polished away, Japanese would speak of a 55% polishing rate or ‘seimai-buai’.
After polishing the rice, it is then prepared for the next steps by first washing (picture) and then simply steaming it (like you would do in your kitchen…)
Since the outer layers have been removed, the polished rice does not contain any natural enzymes that could start a saccarification process. Because of that, we need to add a very special mold called ‘aspergillus oryzae’ or simply ‘KOJI’ to a small batch of the polished and steamed rice. For this process, the rice is spread out over linen cloth on a table in a warm room that has been lined with cedar. After mixing the Koji spores into the rice, the linen is closed and the Koji is left to propagate through the rice over the course of 2-3 days, in the process converting the starch into sugar.
When the Koji rice is finished, the fermentation starter ‘Moto’ is prepared by mixing Koji rice, additional steamed polished rice, spring water and a special Sake brewing yeast.
After approximately 2 weeks, the Moto is transferred into a bigger tank. Within the following 5-6 days, three increasingly larger additions of Koji rice, fresh steamed rice and Water bring the mash to its full intended volume. The total brewing time will be around 20-30 days, depending on quality and style of the intended finished product. Generally, the lower the temperature, the longer the process.
After the Fermentation period is over, the Sake is filtered to separate the particles (especially rice) from the liquid. The picture shows an old-fashioned tune, where Sake mash in linen bags receives careful pressure from a wooden beam – an even more involved method to gather the most delicate Sake is to hang the mash in linen bags high up and let gravity bring out the Sake drop by drop – a great but utterly expensive way to get the best Sake. More typically, however, premium Sake is filtered using a mechanical press.
Not every Sake is filtered - ‘Nigori’ Sake, for instance is little or not at all filtered and thus contains a lot of particles for a milky/creamy consistency; Île Four ‘White’ is a particularly tasty version of this category.
Depending on the type of Sake, after filtration and/or before bottling (or not at all) the Sake is carefully pasteurized at low temperatures to preserve its quality.
The finished Sake is typically aged for a short period (up to 6 months) either in tanks or already in bottles to allow it to mellow and develop its final, refined taste. Before bottling, Sake is typically diluted by using the same spring water that has been used for the brewing process itself. In that way, the alcohol content is reduced from about 20% Vol. after brewing to the typical 16% of premium Sake.