How Is Sake Made?

In Portland, OR this week, I went to go to a great sushi restaurant named Bamboo Sushi. While the sushi was delicious, the sake was out of this world. And it made me realize two things. First, that nine times out of ten, the sake I drink at sushi restaurants sadly is nothing to write home about. Second, that in all my years of studying wine, I’ve never studied sake. I’m a complete beginner. So I took it upon myself to do a little research. And I found so much incredible information that I’m going to devote several articles to this topic. The focus this week: what is sake and how is it made? Over the next two weeks, we’ll cover topics including the different types and how to enjoy it.

An Overview of How It’s Made

esake.com says that the “Five crucial elements… involved in brewing sake [are] — water, rice, technical skill, yeast, and land/weather. More than anything else, sake is a result of a brewing process that uses rice and lots of water. In fact, water comprises as much as 80% of the final product, so fine water and fine rice are natural prerequisites if one hopes to brew great sake. But beyond that, the technical skill needed to pull this all off lies with the toji (head brewer), the type of yeast they use, and the limitations entailed by local land and weather conditions.”

esake.com continues with a high-level description of the brewing process: “Rice is washed and steam-cooked. This is then mixed with yeast and koji (rice cultivated with a mold known technically as aspergillus oryzae). The whole mix is then allowed to ferment, with more rice, koji, and water added in three batches over four days. This fermentation, which occurs in a large tank, is called shikomi… This mash is allowed to sit from 18 to 32 days, after which it is pressed, filtered and blended.”

The Details

Now we’ll go through a few more details, using information gleaned from Urbansake.com, boutiquejapan.com and esake.com.

Step 1: Rice Milling

The rice is gently polished down to isolate the starch in each grain. What does polishing mean? Well, when you polish brown rice to turn it into white rice, you need to polish off 10% of the rice. To produce good sake, you need to polish off between 30% and 50% of the rice!

Step 2: Rice Washing and Soaking

The rice is then washed and soaked to begin introducing moisture into the grain and prepare the rice for steaming.

Step 3: Rice Steaming

Rice is then steamed for about an hour. Sake rice isn’t mixed with water and brought to a boil, as is done with table rice. Instead, steam is brought up through the bottom of the steaming vat to work its way through the rice. This gives a firmer consistency and slightly harder outside surface and softer center. The heat and moisture of the steam actually changes the molecular structure of the starch in the grain, allowing easier breakdown of that starch.

Step 4: Koji Making

This is the key part of the brewing process. Monica Samuels, a Sake Educator for New York Vintners in Tribeca, explains this step as follows: “In order to brew beer, barley… goes through a malting process, where enzymes within the barley help to break down starch molecules and begin converting them into sugars. One of the fundamental differences between sake and beer is this: sake rice does not contain the kinds of enzymes that barley does, so an additional ingredient is needed to help convert the rice’s starch into sugar. Koji-kin is a mold that’s commonly used in Chinese, Korean, and Japanese culture to ferment soybeans as well as to make alcohol. There are many varieties of koji-kin, but Japanese sake is almost always made from yellow koji-kin. To convert sake rice into sugar that can be fermented, koji-kin is delicately distributed over steamed sake rice in a very hot, humid room. Over a period of 48 to 72 hours, the mold is carefully cultivated to grow evenly onto the sake rice. When the ‘moldy rice’ is ready to be incorporated with the other elements of the sake, there is a noticeable, sweet chestnut-like aroma coming from the rice. To the naked eye, each grain of rice appears to be coated with a white frost.”

Step 5: Moto or Shubo

Next comes what is known as the shubo or moto, a seed mash of sorts, which is the fermentation or yeast starter. In a small tank, yeast, water, steamed sake rice and koji rice are mixed together. Over the next two weeks, a concentration of yeast cells that can reach 100 million cells in one teaspoon is developed.

Step 6: Moroni

Finally all the prep work comes together. In the main brewing tank, water, rice, koji rice and the fermentation starter are added. In a process known as san-dan-jikomi, three additions of ingredients are made over the course of 4 days. After the third addition of rice, water yeast and koji, the mash is left to ferment for an additional 20-25 days.

Step 7: Pressing

Once the brewing is complete, the newly created alcohol is separated from the unfermented rice solids left in the mash, usually using an automatic pressing machine known as a Yabuta.

Step 8: Filtration

After pressing, the fine particulate is removed by filtration.  This is often done with a charcoal powder. The charcoal bits have many nooks and crannies that trap particulate, dead yeast, enzymes and any tiny bits of remaining starch.  The charcoal powder is mixed with the sake and run through a chambered filter lined with special filter paper.  The resulting sake is clear and bright.

Step 9: Pasteurization

The next step is pasteurization, where you quickly heat the sake to around 150˚F to deactivate enzymes and kill off any remaining bacteria and yeast. The end result is a shelf-stable product that doesn’t require refrigeration.

Step 10: Storage and Bottling

Most sake is left to age for about six months. Before bottling, it is usually pasteurized again, and water is added to bring the alcohol content down from 20% to about 15%. Machines fill and seal the cap on each bottle. After the bottles have cooled down, they are labeled and boxed for shipping.

I hope you enjoyed this overview of how sake is made. Next week, the different types. The following week, enjoying it!