Sake Brewing Process
Even sake is referred to as "rice wine" it is not made the same way as wine. In wine the grapes are pressed for the juice and then yeast is added for it to ferment. Sake on the other hand is brewed more like beer. In beer grains are mixed with water to make a wort. That wort is then mixed with yeast and fermented. Sake does similar with rice.
The following steps are the bare bones steps for the brewing process. Much like making beer or wine it is a complicate process and much more goes into it. So let's begin!
Step 1: Polishing the rice (Seimaibuai)
This is part of the process in which the brewery determines how much of the outside of the rice to remove. The type of sake the brewery decides to produce will determine how much to polish the rice.
Step 2 : Cleaning and Steaming the rice
Cleaning the rice removes a white powder that is a result of the milling process. This powder is called "nuka". After, the rice is cleaned it will be allowed to soak in the water. This allows the rice to get to a predetermined water content (around 30% of the weight of the rice). Depending on the type of rice and how much it is milled will determine how long the rice will soak.
After the toji (brew master) determines the rice has soaked long enough the rice is then steamed. This is where the rice is typically in a big wooden vat made out of Japanese cedar. This vat is a called a "koshiki". Steam is shot up through the koshiki allowing the steam to surround the rice.
Step 3: Making Koji
After the rice is steamed the brewery will take a batch of that rice and bring it to a temperature controlled room. They will then add the koji-kin to the rice. The rice is then monitored over the next 1.5 - 2 days. The rice will be inspected and mixed to allow the koji to grow on the rice.
Step 4: Shubo
The koji will now be mixed with more steamed rice, water, and yeast. This mix is temperature controlled to allow the yeast to multiply. This typically referred to as a fermentation starter.
Step 5: Moromi
The shubo will be moved to a bigger vat. During this step more koji, steamed rice, and water will be added. This will happen a couple more times over the next 4 days.
Step 6: Fermentation
The moromi will now be allowed to sit and ferment. This is the stage where the koji turns the rice starch to sugars and then the yeast turns the sugars into alcohol. This conversion from starch to sugar and sugar to alcohol is happening at the same time. This is unique to sake and is called parallel fermentation. During this stage the moromi is monitored and has its temperature controlled. This process can take approx. 2 weeks to a month.
Step 7: Pressing the Sake (Joso)
Now the moromi that is all fermented is pumped into cloth bags. The bags are now stacked up and a giant press is used to separate the sake from the rice. Also, there is a method where the sake is not pressed, but rather the bags are hung and the sake drips out.
Step 8: Filtering, Pasteurizing, and Aging.
After being pressed the sake will typically allowed to sit to allow some of the sediment from the pressing to settle. The sake is then filtered depending on the type of sake it is. (For example nigori is coarsely filtered allowing some sediment to remain). All sake is required to be filtered by law.
Breweries also have an option to pasteurize the sake before bottling.
Step 9 : Bottling
Now the sake will be will typically be pasteurized again(but this is optional). It will be mixed with water to reduce the alcohol content to the 15-17% range. It will then be bottled and shipped out to be sold.
Step 10: Enjoyment!
All of that hard work and skill the toji and the kurabito put into brewing the sake is sold to you. This is the part where you enjoy that work with by yourself, with family, or friends. Kanpa!
As I stated earlier this is just an outline on how sake is produced. It takes a lot of skill and knowledge to make the drink we enjoy. The toji and kurabito put their heart and souls into this drink.
I did find a nice video on YouTube that does explain the process well. It also pays off to actually see the steps I think. Please check out the Making Japanese Sake video by the Japan Sake and Shochu Makers Association.