As you have learned in the previous steps, one of the principles of sake making is to extend or hold back a step in the process. Rice is washed in cold water for a limited time so it doesn’t absorb too much of it. Rice is steamed, not boiled, so it doesn’t break down completely. Koji is also only developed so there is still starch and “more to do.”
Fermentation starts with a similar process of gradually adding ingredients, literally “step by step.” Sake also goes through cold fermentation which further stretches out the process.
As you learned in koji making, typically 25% of the steamed rice is used to make koji. The remaining 75% goes directly into the brewing tank after the shubo has been added to the tank. This doesn’t happen all at once, but, rather, in three steps over four days. This is called “san-dan shikomi,” or “three-step combining.” In this combining, the volume of the brew is roughly doubled each time until there is a full brew.
Multiple parallel fermentation is another aspect of sake making that makes it different from every other alcohol in the world. Because the ingredients are added in three stages, saccharification is occurring with some of the rice, while koji rice is already liquifying and converting to alcohol; yeast cannot break down starch but is breaking down sugar, and so forth. Ultimately, all of the ingredients get on the same page, but, at first, there are multiple fermentations happening at the same time.
The remaining 75% of the steamed rice that is not used to make koji or shubo goes directly into the brewing tank.
Start – all ingredients added.
Liquifying and bubbling.
Developing, bubbling up.
Settling in and developing a “cap.”
Ready for pressing.
To eliminate the need for ladders and lots of climbing to look into tanks and test sake, sake makers build their breweries with two levels. The tops of the tanks are accessible from the second floor so rice can be added to the tanks and so brewers can easily monitor and clean them.
If sake makers are going to add distilled spirit, they do so at the end of fermentation, one to two days before pressing. The spirit is usually made from rice but it can also be made from wheat or even sugar cane. It is usually 40% alcohol by volume when added and neutral in taste and smell. Adding alcohol will end the fermentation. While this can make the sake fruitier because there is more residual sugar, the spirit itself can make the sake more dry. Spirit will make the sake lighter in weight on the palate and it will smooth out the “edges.” Junmais will be ricier, or grainier, while honjozos will be more rounded. Sake makers never want the alcohol to show and using it is an art.
The practice was used during World War II, when rice production fell and sake makers needed to bulk up yields. However, as sake making technology and quality advanced and competitions sprung up, sake makers found that their sakes with distilled spirit earned higher scores. The spirit sealed in and brought out flavors and aromas. Thus, the technique proved its merit.