You may have seen that a label on a Sake bottle shows several numbers besides alcohol percentage. One of them is Seimaibuai, meaning rice polishing ratio and it mainly determine the Sake's flavor and aroma. In 'What is different from wine?' article, we explain how alccoholic fermentation for Sake occurs. Before alcoholic fermentation occurs, rice needs to be 'sweet'. Rice contains starch and Koji mold converts it into sugar. As you can see in the image below, rice for Sake has the white and opaque part at the center. It's called Shinpaku, literally meaning the white in the center, and most of its component is starch. The external part of rice contains protein, vitamin and lipids which interrupt nice Sake aroma and create off-notes flavor. Therefore brewers mill rice to remove the unnecessary external part to make sophisticated rich aroma and flavor. Rice polishing ratio (Seimaibuai) is the degree to which the rice used in brewing has been milled or polished and it's culculated as follows:
Weight or the remaining rice after polishing (kg) ➗ Weight of brown rice (kg) ✖️ 100 = Rice polishing ratio (Seimaibuai, %)
So if rice polishing ratio is 60%, it means that the rice had the outer 40% groud away. It's a bit confusing but remember; the smaller the rice polishing ratio is the more its rice was polished. The rice polishing ratio is important to grade Sake. For Daiginjo, its rice polishing ratio has to be below 50%. That's why Daiginjo tends to be expensive because brewers need to put much time and effort to polish the rice because Shinpaku is hollow and soft compared to the exterior. But it doesn't meant that Sake with lower rice polishing ratio is better. Although exterior of rice can interrupt aroma and flavor, it can also cause nice Umami if it's suitable amount. Therefore, you can remember like below: - If rice polishing ratio is low like below 60%, the Sake has rich aroma and refreshing, clear and sohisticated taste. - If rice polishing ratio is high like above 70%, the Sake has mellow and rich Umami taste. Our production page shows rice polishing ratio so please check and try Sake to find out how much rice polishing ratio you prefer!