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Kenbishi in Nada can do its own rice-polishing in-house. Many breweries cannot.
Polished rice at the Daishichi Brewery.
Rice used to be hand washed, but now compact machines like this at the Kamotsuru Shuzo Brewery in Saijo, Hiroshima make the job easier.
Not all rice polishing is the same, either. Typical milling results in little beads of rice for brewing. However, the starchy white cores in, for example, the Yamada Nishiki rice variety are not round, but flat spheres. If you cut open a grain of Hyogo-grown Yamada Nishiki, the starchy core looks like the filling in an ice-cream sandwich or a moon pie. If Yamada Nishiki is polished to 40 percent with a typical mill, the tips of each grain will be removed, but the midsection, with all its unwanted proteins and oils, remains. The flat rice-polishing method, devised by Tomio Saito of the Tokyo Regional Taxation Bureau in the late 1980s, aims to reduce that by polishing away the middle. The Daishichi Brewery in Nihonmatsu furthered that technique with its in-house method known as “super-flat rice polishing.” The average width of a Yamada Nishiki grain is 2.1 mm, and according to brewery president Hideharu Ohta, conventional rice polishing only brings that down to 1.9 mm. “So for Yamada Nishiki, with a 35 percent polishing ratio, lengthwise it’s actually polished to 20 percent, but the middle is only polished to 90 percent,” says Ohta. “It’s like you’re blending rice with two different polishing ratios.” Instead, the super-flat method can bring the width of a 2.1mm grain of Yamada Nishiki down to 1.5mm.
Washing, Then Soaking
The rice is washed to remove any fine powder (called nuka in Japanese) that may have been left on the grain during polishing, which would negatively affect fermentation, because the point of polishing is to remove the outer layers. Rice can be machine washed or washed as it’s piped through the brewery. The delicate grains of polished rice can be washed by hand or by hi-tech rice-washing contraptions.
After washing, the rice is soaked. Soaking slightly polished rice takes a bit of time, while finely polished ginjo grain soaks up water in minutes; the process is monitored by stopwatch. Brewers must make sure the grains absorb the desired amount. If the rice soaks too long, it becomes sticky once steamed, making it hard to work with during the koji making. Soaking is one of the most important steps in making sake.
Rice steams at Tamanohikari in Fushimi.
A brewer scoops out steamed rice at the Miyoshino brewery in Nara.
A peek inside an enclosed brewing tank.
Steaming
The soaked rice isteamed in a large tub or tank called a koshiki for around an hour. Water is not added, because the rice has already soaked in water and contains the necessary moisture. Ideally, the resulting steamed rice has a hard exterior and a soft inner core. The steam breaks down the crystalline molecular structure of the rice starch, setting the stage for the enzyme reactions that follow. Koji-mai is the steamed rice destined for koji making, while steamed rice that’s cooled and added to the main-mash is called kake-mai. Out of each steamed batch of rice, the breakdown between koji-mai and kake-mai is around 25:75, but a percent is also set aside for the yeast starter rice.
Koji Making
Steamed rice is high in starch, but doesn’t have enough sugars for yeast to eat and produce alcohol. Enter koji. In English, the word “koji” is used interchangeably to refer to the mold and the inoculated rice. In Japanese, koji-kin means the koji mold spores; in sake making, koji refers to rice inoculated with the mold. The term kome koji (rice koji) is also used, typically shortened to simply “koji.”
Around 20 percent of the steamed rice is cooled to 86–95°F (30–35°C) and transferred to a sauna-like room paneled with cedar or stainless-steel called the koji muro, where the temperature is 82–86°F (28–30°C) and the humidity is 80 to 90 percent. It is placed on a large table and covered with a cloth for a few hours so the temperature and moisture can equalize.
The steamed rice is unwrapped and spread out. Koji mold spores are then sprinkled over the rice; the mycelium will work its way inside the grain, seeking moisture in the starchy core. The rice is kneaded into a mound and covered with a cloth to prevent loss of heat and moisture. Another method is for breweries to sprinkle koji-kin on the rice as it comes down the conveyor belt on a cooling machine. For mass-produced sake, rice is inoculated mechanically with koji-kin spores as it passes through tubes.
Over the next 20 hours, the rice is unwrapped and kneaded twice more. When white mold dots the grains, the rice is moved into wooden trays or boxes. During the next eight hours, the rice is moved around in the trays, which are stacked and restacked in the koji muro to ensure uniform heat and moisture. Some breweries use cedarwood trays; others use plastic or metal. Koji for mass-produced sake can also be made in automated temperature-controlled koji chambers with large combines that turn the koji. There’s more than one way to make koji.
The chemical process continues to give off heat until the temperature surpasses 100°F (38°C). The koji muro becomes a sauna, fogging up your glasses and drenching your shirt, explaining why some brewers work shirtless and barefoot. Once koji-kin covers most of the grain and koji’s telltale chestnut aroma hangs in the air, the koji is removed from the room, spread out on cloths and raked. Some breweries make patterns in the koji to indicate that it’s finished, or to indicate which batch of sake the koji is slated for. Sometimes, however, the designs are just that—designs.
This is the traditional koji-making process. Another method is to place hand-inoculated rice in special temperature-controlled chambers that look like ovens. There are also automated machines that stir massive amounts of rice with giant rotators. Ultimately, what matters most is the quality of koji produced.
Yeast Starter
As previously mentioned, the Japanese word for yeast starter is moto (which means the “base” of sake), or shubo (which means “the mother of sake”). Good shubo means good sake, so brewers aim to make excellent (and healthy) yeast starter for brewing. This is why starter is used to create a small, pure yeast culture of lactic acid that protects the starter from undesirable bacteria. Lactic acid either propagates naturally or is added. The main starter styles are kimoto, its offshoot yamahai, and sokujo-moto.
Kimoto
Kimoto (literally “pure yeast starter”) is one of the oldest styles of moto still used, dating from the 1600s. There is no official definition of how to make kimoto, nor are there any regulations that define the style. Generally, it’s characterized by mashing the rice and koji together with the oar-like poles in a
