In a previous blog, What is Sake we discussed that sake is a fermented rice beverage made from polished rice, water, yeast, koji mold and, sometimes, brewer’s alcohol. This blog is an in-depth explanation of how sake is brewed.
1. Rice polishing/milling “Seimai” － The exterior ‘brown’ part of rice grains contain protein and fat, which are not desirable traits in sake. The exterior of the grain needs to be milled away for a cleaner flavour and to access the rice’s concentrated starchy centre. The amount of rice polished away varies, resulting in a different style and flavour of sake. If more rice grain is polished away, then the flavour will be purer. A higher polishing rates does not necessarily mean the sake is of higher quality, just a different style. Here is a list of the classifications of sake and their corresponding polishing rates. For reference, white table rice is polished down by only 5%.
- Sake with Brewer’s Alcohol
- Honjozo (min. 70% remaining)
- Honjozo Tokubetsu (more rice polishing than standard Honjozo or made using a special production method)
- Ginjo (min. 60% remaining)
- Daiginjo (min. 50% remaining)
- Sake without Brewer’s Alcohol
- Junmai (not regulated but typically 70-80% remaining)
- Junmai Tokubetsu (more rice polishing than standard Junmai or made using a special production method)
- Junmai Ginjo (min. 60% remaining)
- Junmai Daiginjo (min. 50% remaining)
*There is more info on brewer’s alcohol below.
2. Washing and soaking the rice － Rice is washed and soaked to clean away residue from polishing and increase the grains’ moisture levels. The moisture will be beneficial later in the brewing process by encouraging koji mold to work towards the grain’s moist starchy centre.
3. Steaming the rice － Sake rice is steamed in vats. The brewers want the rice to have a firm exterior and a soft interior. This encourages koji mold to work towards the grain’s moist starchy centre.
4. Rice is separated in two and prepared for fermentation － The rice is separated for the Koji and Moto.
- Preparing Koji (rice at the top of the tank) － sake rice does not have easily accessible sugars for fermentation. To solve this problem, brewers make Koji Mold, rice inoculated with a fermentation culture called Aspergillus Oryzae. Aspergillus oryzae is a key ingredient in many Japanese staples like soya sauce, miso and mirin. The Koji Mold will then break down the rice starch into sugars, and then those sugars are ready to be fermented with yeasts.
- Preparing the Moto/Shubo/Yeast Starter (rice from the bottom of the tank) － For the Moto, yeast, rice, water and Koji are combined. There are two goals: to create a high enough concentration of yeast cells to support further addition of rice and to create lactic acid. Lactic acid can be created in four ways and results in different profiles in the finished sake:
- Kimoto － The original Moto production method that allows for the natural build-up of lactic acid and requires mashing the rice with long poles to encourage scarification. Kimoto sakes have rich umami flavours and higher acidity.
- Yamahai － Created in 1909, this is an update/alternative to the Kimoto method that still allows for the natural build-up of lactic acid and does not require mashing the rice with long poles. Yamahai Sake, while milder than Kimoto, has rich umami flavours and high acidity.
- Sokujo － The so-called “modern” or “fast” Moto method where lactic acid is added manually at the beginning of making the Moto. Sokujo sakes are aromatic, clean and dry.
*Note that Koji is required in the Moto to create sugars for the yeast. Sake undergoes parallel fermentations: koji mold (starch to sugar) and yeast (sugar to alcohol).
5. Sandan Shikomi － After the Koji and Moto preparation, brewers combine the Koji, the Moto, water and more steamed rice. Further additions of rice, water, and koji are done in three stages so that there is a high enough concentration of yeast cells to support further addition of the rice.
6. Moromi Fermentation － Once the final addition to Shikomi is complete, the main fermentation takes place for 15 to 25 days.
7. Jozo － At this stage, brewer’s alcohol can be added for Honjozo styles. Why is brewer’s alcohol used? In modern times, brewer’s alcohol fine-tunes aromas and flavours in sake. The alcohol is essentially tasteless and can make a sake rounder, drier, smoother and lighter. Just because brewer’s alcohol is used does not mean the sake is higher in abv because sake can still be diluted with water. For a high abv bottle (20% abv), look for the term Genshu = not diluted.
8. Pressing － Pressed with Assakuki (balloon-press air compressor not gentle enough for high-quality sake), Fune (box press) with shibori fukuro (porous cloth filter bags), Shizuku teardrop (gravity press), or Fukuro-tsuri (hanging bag, the free run sake used for most exclusive Junmai Daiginjo)
9. Filtration －Once sake has settled, the brewers often filter it through activated charcoal. Non-filtered, ‘freshly squeezed’ sake called is called Shiboritate.
10. Pasteurisation － Pasteurisation deactivates heat-sensitive enzymes and kills microorganisms left over from fermentation. Unpasteurised or raw/fresh sake is called “Nama”. It must be stored between -8 to -5C.
11. Blending －Blending multiple batches of sake that use the same ingredients and methods or like HeavenSake blending completely different sakes (rice and style) to make something new and complex. Water is often added at this stage to dilute sake. In Japan sake must be below 22% abv by law.
12. Maturation －Sake rests in tank or bottle for 2-6 months. Taru Sake is aged in cedar barrels.
13. Release － Most sake is meant to be consumed 6-18 months after release.
- Brewing year (BY) from July 1 to June 30. Sake releases are sold by season.
- From the current year, sake is called Shinshu = new sake.
- The fall release, which has been resting in tank, is called Hiyaoroshi. This is a rounder and mellower sake.
- The summer release is called Natsunama.
- Made in 1st BY but released in the next BY is called Koshu “aged sake”. Sake oxidizes so these will often be a dark amber colour.
- Sake release in the following 3rd BY is called Ogoshu “extra aged sake”.