Sake School: All About Sake Rice

For thousands of years, rice has been Japan's most important agricultural product. Once a form of currency in Japan, rice is now used to produce many other goods, such as flour, vinegar, mochi, and of course, sake. However, the type of rice usually used for making sake, called sakamai, is pretty different from the kind of rice that we are accustomed to eating. The main difference is that the pure starch component of sakamai, called shinpaku, is separate from the rice's protein and fat. Because of that, it's possible to polish the rice, removing proteins and fats and isolating the pure starch.

How Sake Is Made

The sake brewing process starts in the fall, when the rice is harvested. The rice is polished in a process called seimaibuai. As the outer layers of the sake rice (consisting of mostly proteins and fats) are removed, the starch is exposed. Then the rice is washed, soaked, and steamed. At this point, a type of mold called koji-kin is introduced into the steamed rice and encouraged to grow. This mold helps convert the rice's starch into the sugar that's needed for fermentation. Once the koji is established, sake brewers create a yeast starter: They add yeast to a small batch of rice, koji, and water, so that the yeast cells can begin to eat and reproduce. The brewers then add gradually increasing amounts of rice, koji, water, and yeast to the fermenting tank. After fermentation is complete, sake brewers take additional steps depending on the style of sake they wish to produce, including adding distilled alcohol or diluting with water, filtering, and pasteurizing. We'll cover these processes in more detail later.

A Guide to Sake Rice

Different types of sake rice each behave a bit differently during the brewing process and result in different-tasting final product. The end result also depends heavily on the skill and intent of the brewmaster. Here are a few notable types of sake rice. Please note, the locations mentioned are simply locations of rice fields—any region of Japan can use any type of rice, and there isn't a sake appellation system.

Yamada Nishiki

A large majority of sake brewers consider Yamada Nishiki to be the best possible rice for brewing daiginjo, which is the highest grade of premium sake. It is known for producing delicate, fragrant, feminine styles of sake. Its ability to absorb water and dissolve quickly into the sake fermenting mash continue to make it a favorite amongst brewers. Since it's a softer rice, Yamada Nishiki must be polished much more slowly than other types of rice to avoid breaking. This is the most expensive strain of sake rice. Hyogo is the most prolific region for Yamada Nishiki, although it can also be found in Fukuoka, Tokushima, and Okayama. Yamada Nishiki is not a pure strain of rice, but a hybrid between parent strains yamadabo and wataribune.

Gohyakumangoku

Gohyakumangoku is the second most popular sake rice in Japan, with the earliest harvest I have heard of (this year's harvest began in mid-August, while Yamada Nishiki is typically harvested in October). This rice is most commonly found growing along the northwestern coast of Japan, although the region of Niigata is often credited with putting this rice strain on the map. This type of rice helps sake brewers in Niigata produce their classic style of sake, which is clean, light, and refreshing.

Miyamanishiki

This rice is widely used in northern Japan and is known for producing rich, full bodied sakes. Known for its prolific growth and resistance to cold weather, Miyamanishiki is often used to create hybrid rice strains for very cold climates. Some examples are Dewasansan in Yamagata, Aki no Sei in Akita, and Yume no Kaori in Fukushima.

Koshi Tanrei

This is a relatively new hybrid rice strain, used almost exclusively in Niigata Prefecture. Koshi Tanrei is a hybrid of Yamada Nishiki and Gohyakumangoku, and can be polished very far down. The resulting flavor is a marriage of Gohyakumangoku's clean and dry style with Yamada Nishiki's fragrant, floral characteristics. Brewers in Niigata have been working to use local ingredients in their sakes, but because Yamada Nishiki is predominantly grown outside of Niigata, it was difficult until the development of Koshi Tanrei for these brewers to make daiginjo grade sakes using local rice.

Omachi

Omachi is known for rich, earthy flavors that are some of the easiest to identify when tasting sake. This rice has a bold character and a reputation for being more difficult to use than Yamada Nishiki. Omachi is softer than Yamada Nishiki and dissolves into the mash more quickly. It is said to have originated in Okayama.

There are certainly many more types of sake rice being used today; what I've listed here are simply some of my favorites and some of the most commonly used strains. Though I've noted some characteristic flavors, each type of rice can produce a myriad of different styles, aromas, and flavors, and many sake producers use more than one type of rice in a single sake, often saving the premium rice for the koji, but using a lesser rice for the rest of the process.

Confused about koji? Don't worry, we'll cover it in further detail next week.