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What is Sake?
Sake, commonly referred to as Japanese rice wine, is an alcoholic beverage produced from fermented rice, water, koji mold and yeast. Sake (酒), in Japanese, refers to any alcoholic drink. However, the English term for sake is referred to as nihonshu (日本酒), which means Japanese rice wine and is the actual topic of discussion here.
How Sake Is Made
In contrast to its nickname of Japanese rice wine, the brewing process for sake is more similar to beer than to wine. In both sake and beer, starch coverts to sugar and then ferments into alcohol, while wine relies on the natural sugars in fruit to ferment. The process of making sake does have other differences to making beer. The first difference is that it is made from rice and choosing one of the dozens of different types of sake rice is the first step in making sake. After the rice is chosen, it then needs to undergo polishing.
Polishing the Rice
Polishing rice is the term used to describe the removal of the outer layers of the grain of rice. The husk, bran and germ are removed, which does result in a loss of some nutrients. However, these produce undesirable flavors when brewing. Thus, the amount removed for sake rice is typically much larger than for rice used for food. The amount of grain remaining after polishing is referred to as the rice polishing ratio. For example, food normally has around 8% removed in polishing and therefore has a ratio of around 92%. Sake, on the other hand, normally has ratios around 70% to 50%. Typically, the more polished the rice, the better the taste and the more expensive the final product.
Rinse, Soak and Steam
With the appropriate rice obtained and polished, it is then time to clean it and steam it. To do so, the rice is first rinsed off and then soaked. After washing, the rice is then steamed and cooked. With the rice prepared, most of it will be used directly for fermentation. Some of the rice, about 20% or so, is used to create koji rice using the koji-kin mold spore.
Adding the Mold (Koji-kin)
Koji-kin is a type of mold used in making many fermented foods in Japan, like miso paste, soy sauce, and sake. The koji-kin mold spores are spread across steamed rice and are kept in a warm and humid environment so they can germinate. This causes them to release enzymes that covert the starches in the rice into sugar instead. The rice made from this process is simply called koji and is used in the yeast starter, shubo, during fermentation.
Fermentation Process
The fermentation process is broken down into three steps called the sandan shikomi. The three steps are referred to as the hatsuzoe, nakazoe, and tomezoe.
The first step in the fermentation process starts with our shubo yeast starter, which consists of steamed rice, water, yeast and the koji rice that was made in the last step. More steamed rice, water and the koji-kin are then added to our shubo starter to create a mixture known as the mash or moromi. With this mixture the yeast now has food from the sugar to start producing alcohol and the koji-kin added can continue to germinate and turn the starch in the steamed rice into more sugar for the yeast.
The fermentation process is conducted at a much lower temperature than the original creation of the koji rice. This is to ensure the yeast has a steady gradual supply of sugar to eat. The simultaneous creation of sugar and alcohol is what differs when creating sake compared to beer. The process is called multiple parallel fermentation and is unique to sake.
After allowing the mixture to rest for a day, the second step begins, which is the addition of more koji, steamed rice, and water added to the mixture. The same goes for the third step, which sees the final addition of koji, steamed rice, and water added to the moromi.
After the third step, the mixture is then left to ferment. The length of fermentation varies, but is normally around 20 days with some taking as long as 35 days. The fermentation length varies because it depends on when the yeast has died out from the alcohol. The yeast produces both alcohol and carbon dioxide and the release of carbon dioxide creates bubbles in the mixture. Thus, you can tell the yeast has mostly died when all of the bubbles have disappeared.
Time to Press and Pasteurize
Once the fermentation is complete, the moromi needs to be pressed to extract the sake. The leftover solids are the sakekasu (酒粕) or sake lees, which consists of the dead yeast and other particles. The sake lees aren’t wasted and can be used in cooking, or oddly enough, even skincare products.
Once pressed, the sake is then filtered to remove unwanted color and flavor.
At this point the sake is still ‘alive’ as some yeast may still have survived up until this point. Also, bacteria can grow and turn the drink sour if it’s not pasteurized. To pasteurize, it is heated to around 65°C (149 °F) for 30 minutes. However, not all sake is pasteurized. Namazake (生酒), which means raw sake, is left unpasteurized and has a sharper taste and stronger smell. The trade off is that it also needs to be kept under 0°C to prevent it from spoiling.
Sake also benefits from being left to mature, so it’s kept in storage for around 6 – 12 months. That’s not to say that vintage is important in sake. Most sake is drunk within a year and its flavor doesn’t change with long term aging like wine. After storage, most sake is pasteurized a second time, which ensures its shelf life.
Once the pasteurization and aging is finished, it is then time to bottle, label and sell the finished product.
