Traditional Culture of Japan - Portal site of traditional crafts and culture

Making sake: rice polishing


Making sake begins with rice polishing, or seimai. The rice is milled to remove the unwanted constituents in the outer layers of the rice grain.


Polishing rice for sake brewing is more time-consuming than polishing rice intended to be eaten, and also subject to more rigorous production control, because much more of the grain is removed when the rice is to be used for making sake.


Shiny polished rice
When rice is harvested, it is whole grain brown rice (genmai in Japanese). Normally, rice is not eaten in this form, but is polished to remove some of the outer layer of the grain, making it easier to eat. Rice that is to be eaten generally has a rice polishing ratio of 90%, meaning that 10% of the grain is removed by polishing, and 90% remains.


Rice intended for use in sake production, on the other hand, has a rice polishing ratio of less than 70%, and in some cases, less than 50%. In other words, considerably more of the grain is polished off.


The outer layer of brown rice contains constituents such as protein and sugar that would have an adverse effect on sake brewing. If unpolished rice were used for brewing sake, the final product would have unpleasant flavors. To avoid this, rice is polished. The flavor of sake varies depending on how much the rice used to make it was polished.


Among the varieties of rice there are some that are particularly suited to sake brewing. These are called shuzō kōteki-mai. They have a large grain size, and the cloudy white portion at the center of the grain, called the shinpaku, is also relatively large.


Because the shinpaku portion of the rice grain is the most important part for sake brewing, it is wasteful to polish so much that some of the shinpaku is discarded. In other words, up to a point, the more the rice is polished, the finer the flavor of the sake, but over-polishing is inefficient.


Sake rice that has been polished to reveal the shinpaku portion at the center of the grain has a shiny white appearance.


To polish rice to a ratio of 70% is a quick, easy procedure. Beyond 70%, however, the speed is reduced. In addition, by the time the ratio reaches around 50% to 60%, almost all of the non-starch constituents of the grain found in the outer layers, such as sugar, have already been removed.


As more of the grain is polished off, the likelihood of splitting the grain becomes higher. It becomes difficult to keep the shape of each individual grain when a large proportion of it is polished off.



When a large proportion of the grain is polished off, there is a lot of unwanted material made up of polishings and broken pieces of grain. So while it is possible to make better sake by removing more of the outer layers, the amount of wastage also increases at the same time.


After polishing, rice is set aside for “karashi”
Rice, having been polished, is not immediately used in the next step of the brewing process. The reason is that during the polishing process, the rice grains lose moisture because of factors such as the heat of friction.


In the next stage of the brewing process, the polished rice needs to be immersed in water. If the rice is placed in water in its dry, weakened state, it absorbs water very quickly and becomes sticky. Rice in this moistened condition is tender and easily damaged.


So instead, the rice is placed in bags and set aside for some days at room temperature, and then chilled. During this period, the rice absorbs moisture from the air. This process is called karashi.


If the karashi process is performed, the rice, which is dry after the polishing process, will gain moisture so that when it is eventually immersed in water, the water will not so rapidly penetrate the rice. The rice will expand but it will not be so fragile. The likelihood of damage is much lower. For this reason, the karashi process is an essential step in brewing sake.


Karashi takes about one month. To make good sake, it is necessary to allow for this period of time.

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