Continuing from the first article in our series on sake, we look in more detail at the process of making the quintessential Japanese alcohol.
Step by step
The production of sake involves seven steps.
The differences in the end products depend on the quality of the rice and water, the variations of temperatures, the koji mould, and the skills of the sake maker.
The process begins with polishing the main ingredient – hulled rice. The rice is polished to remove any impurities and to give a smoother taste.
As it passes through a special polisher, the rice kernel is milled to remove the outer layer of each grain, exposing its starchy core.
Sake is often categorised by the “rice polishing ratio,” which measures how much of the outer grain is removed through polishing.
Rice is polished down to a certain percentage, affecting the final taste of the sake.
A lower number indicates a high milling rate and a more “premium” product that is lighter in body and subtler in aroma.
The more rice has been polished, the higher the classification level.
Good sake is usually polished to about 50% to 70% (i.e., from 30% to 50% is polished off).
Two common terms are ginjo—which specifies that 60% or less of the grain is left – and daiginjo, meaning 50% or less.
Saito Junmai Ginjo Genshu and Saito Junmai Daiginjo
While more polish means a higher grade—and usually a higher price—it does not definitively make for “better” sake.
2. Washing, rinsing and soaking
The next process is to wash and rinse the polished rice to remove the bran. It is then left to soak in water. Rice that has been milled more will absorb water faster, reducing its soaking time. This process can be done in a few minutes or overnight.
The soaked rice is then steamed in a steamer. Then the steamed rice is usually divided into two batches – one for fermenting and the other to become koji.
4. Creating koji
Koji is steamed rice inoculated with koji mould. This secret ingredient will become the sugar for the yeast, creating alcohol and carbon dioxide.
To create koji, the steamed rice is laid flat on sheets in a very humid room with dead air; this room is called the “koji room” and is regarded to be sacred by sake brewers.
To make good koji, the room temperature needs to be optimal. The spores of the aspergillus oryzae mould – which is also used in the fermentation of soy sauce - need to be spread out evenly over the steamed rice.
After a few days, koji is created, giving the rice a sweet chestnut aroma.
Fermentation occurs in different steps; depending on the brewery. All the steps can happen in the same tank.
The fermentation starter is called shubo: a mix of steamed rice, water, yeast and koji. This basic mixture will increase over the days as the yeast multiplies.
After several weeks, the shubo becomes the “mash” or moromi, basically the cake on the top.
More water is added regularly over the days.
The yeast will then convert into sugar and alcohol; this is when fermentation occurs. The entire process usually takes around 35 days.
6. Sake pressing and filtration
Once the moromi is completely fermented, it is passed through a press that will remove the moromi and leave a translucent liquid – the sake.
The sake is then filtered.
7.Sake pasteurisation and bottling
The sake is heated to 60°C -65°C to kill bacteria and placed in cold storage where it matures before being bottled.