Sake Making Basics
The word ”sake” is synonymous with Japan and its culture. As the country’s traditional alcoholic beverage, it has been tentatively dated all the way back to the Yayoi Period (300 BC-250 AD), as the era when rice cultivation itself was introduced to Japan from China, thus providing one of its main, and essential, ingredients.
Unlike wine, which goes through a single stage of fermentation, sake is more akin to beer in some respects. Making use of grain as the base ingredient requires the conversion of starch into sugar before brewing can commence, in a chemical process known as saccharification. Unlike beer, where this process takes place in a separate stage — commonly known as “malting” — sake is unique in the world of brewing through its use of a complex process referred to as “multiple simultaneous fermentation”. In short, this requires the conversion of starch into sugar (saccharification) and that sugar into alcohol (fermentation) to occur at the same time within the same brewing vessel. This process also allows sake to achieve the highest natural alcohol content of any fermented beverage in the world.
At its most basic, there are three primary components that go into making sake: rice, rice koji, and water. In less tangible terms, credit must also be given to the years of experience and finely-honed skills required for the “toji” (brew master) to produce a good sake, as the entire brewing process is essentially carried out by hand and with a high degree of precision. In terms of physical commodities, however, bottled sake is made up of at least 80% water, so selecting the right water source and properties is crucial if you want to brew a really good sake. Choosing which rice variety to use and how to process it also contributes greatly to the quality of the finished sake. All of these decisions rest with the “toji”, and require their skills and experience to successfully navigate them.
From raw materials to bottle, the sake-making process can be broken down into five broad stages:
- Rice processing
- Rice koji production
- The “shubo” (fermentation starter)
- The “moromi” (fermentation mash)
- Pressing and bottling
Overall, the whole process takes around four-to-six weeks before pressing, after which it is generally aged in tanks for between two weeks and up to a year (or sometimes even longer) before final bottling.
Stage 1. — Rice Processing
The first stage involves polishing the harvested rice in order to prepare it for brewing. Unlike your typical table rice, where about 10% of the outer layer is removed before packaging, sake making begins with about 30% of the original kernel being polished away — and for the really premium sake, sometimes as much as 70% or more, leaving only 30% of the original rice kernel.
After polishing, the rice is washed, to remove the “nuka” (bran powder), and then soaked in water until it absorbs enough moisture for steaming. Aside from the obvious matter of scale, there are differences with domestic cooking here as well, as the rice itself never comes into direct contact with the boiling water. Instead, a “koshiki” (steaming vat) is used to funnel steam up from below and through the vessel, literally “steaming” the rice. The end result is a firmer consistency than culinary rice, with a slightly hard surface and a soft center.
After steaming, the rice is then cooled and divided into two batches, with about 20% of the total going into making rice koji and the remainder destined for the moromi. Around 5-to-6 % of the total on each side is then taken to be used in making the initial “shubo” (fermentation starter).
Stage 2. — Rice Koji Production
The initial step in the all-important process of making rice koji is to transfer the cooked rice to a dedicated koji-making room, where the humidity is carefully regulated and the temperature controlled at 35°C. After being laid out on a flat surface, the steamed rice is dusted with the koji mold (aspergillus oryzae) before being loosened up and kneaded together to fully incorporate them. Variations on this process are also essential in the production of a wide range of other Japanese foodstuffs and beverages, such as spirits (shochu), soy sauce, vinegar, and miso — all requiring the use of certain strains of koji mold.
Following the initial inoculation phase, the batch is constantly checked, re-arranged, and mixed to ensure that the koji mold is distributed evenly throughout the rice. This process takes around 48 hours to complete.
Stage 3. — The “Shubo” (Fermentation Starter)
With the koji mold beginning to convert rice starch into sugar, we come to the “shubo” (fermentation starter) stage, in which yeast will play an important role. This process begins with mixing a portion of rice koji, steamed rice, and water in a small tank, along with a culture of pure brewing yeast. At this point, either a small amount of lactic acid is added (according to the modern, accelerated method) or lactic acid is allowed to propagate naturally within the brew (the traditional way). Lactic acid both protects the yeast from other unwanted bacteria and provides an acidic environment in which the yeast itself will thrive. Depending on which method is chosen, this starter phase will take about two-to-three weeks to complete.
Stage 4. — The “Moromi” (Fermentation Mash)
Once the fermentation starter is ready, the next step is to scale it up to form the “moromi” (fermentation mash). This is prepared by transferring the “shubo” (fermentation starter) to a larger fermentation tank, where the remaining rice koji and steamed rice from previous stages are gradually recombined, along with extra water. This scaling up process takes place at three intervals spread over four days, after which the “moromi” is complete. This “three-step brewing method” — or “sandan jikomi” — is followed in order to avoid diluting the acidic environment within the “moromi”, which protects and aids the yeast throughout fermentation.
Once the scaling up process is complete, the combined saccharification and fermentation process (or “multiple parallel fermentation”) continues for the next two-to-four weeks, throughout which the temperature and various other factors are closely monitored and adjusted accordingly. Depending on the type of sake being produced, a small amount of distilled alcohol may be added to the “moromi” at the end of this stage, just before pressing.
Stage 5. — Pressing and Bottling
Once the alcoholic fermentation is complete, the “moromi” (fermentation mash) is pressed in order to separate the sake from the undissolved remnants of the rice grains (sake lees or “kasu”). This is done either using an automatic pressing machine or — in the more traditional method — using a “fune” (a large wooden box in which the “moromi” is placed in cotton bags, with a weighted press bearing down on the lid). The leftover sake “kasu” is separated after the pressing is complete, but still contains around 8% alcohol, and is considered a nutritious ingredient in various traditional dishes or for pickling.
After pressing, the sake is allowed to sit in a tank for around 10 days, to allow any remaining sediment to settle. It then proceeds to the filtration process, where bamboo charcoal is used to remove certain unwanted flavour elements and clarify its natural amber hue. Next comes pasteurisation, where the sake undergoes heat sterilisation (usually through immersion in hot water, like a double boiler) in order to deactivate certain enzymes and kill any bacteria that may result in unfavourable flavours, colours, or outright spoilage.
Following this, the sake is generally stored in tanks for around six months, in order to enhance the flavour profile before bottling. Once sufficiently matured, the sake is then “cut” with pure water — bringing the alcohol content down from nearly 20% to around 16%, on average — and also blended between batches for consistency. A second pasteurisation is undertaken just before bottling, to avoid refermentation or spoilage, before the finished sake is finally shipped.
As you can see, the art of sake-making is a process steeped in both tradition and a high degree of complexity. We hope this brief guide to the major elements and step by step processes of sake-making will give you a greater understanding and a deeper appreciation of this truly unique world beverage.
Feel free to check out our other blog posts here. Until next time, kanpai!