Each step in the sake-brewing process is critical to sake production, but rice polishing in particular garners a lot of attention due to its influence on sake categorization like Junmai, Junmai Ginjo, and Junmai Daiginjo (official called : Junmai Type ) or Futsu-shu, Tokubetsu Junmai, Ginjo and Daiginjo ( official called : Ginjo Type)  and sake pricing. Rice polishing is the process by which the outer layers of a grain of rice are polished or milled away. Here, we discuss the purpose of rice polishing, how it’s done, and its effects on the categorization and flavor profiles of sake.


Rice Polishing Ratios (RPR)


What is seimaibuai or 精米步合?

“Seimaibuai” (rice polishing ratio) is a description of the percentage of grain that remains after a part of the rice has been polished away. For example, sake with 70% RPR means that about 30% of the rice’s outer layer has been milled away. You can usually find a sake’s rice polishing percentage on the sake label. Easy Dassai is directly related the product name to the rice Polishing Ratio, exp: Dassai 23 , meaning 23% RPR means that about 77% of the rice’s outer layer has been milled away.


Dassai 23 ( RPR:23%)


From Brown Rice to idea Seimaibuai level 40%


Why is rice polishing necessary?

 Rice polishing shaved away protein and fat, leaving the starchy interior (“shinpaku”心白) used in saccharification 糖化 (the conversion of starch to sugar), which is necessary to brew alcohol. Brewers determine the level of rice polishing and gently mill away these elements to achieve the desired taste profile of the final product.


Shinpaku ( Rice Starch）


These days, breweries use vertical rice polishing machines that are very precise and automated; these machines are a far cry from the traditional methods of long ago!

Rice Polishing Machine


Higher rice polishing ratio indicates that a greater percentage of the original rice grain remains after polishing. This type of sake typically boasts rich umami from the rice and fuller body. Beside that, lower rice polishing ratio represents sake brewed with more milled rice, which often results in cleaner and fruitier taste notes. Many brewers make products with different rice polishing ratios under the same brand to cater to different preferences and occasions.


Let’s see the below products from Niwano Sake for more easy to understand about what is Rice Polishing Ratio.




From Left to Rights:
Niwano Junmai Daiginjo 45 ( Seimaibuai :45%), Niwano Junmai Daiginjo 50( Seimaibuai :50%),  Niwano Junami Ginjo 60( Seimaibuai :60%)

Although a lot of attention is given to rice polishing ratio by sake professionals and industry competitions, it’s important to not get too caught up in analyzing digits. You might miss out on other good sake if you rely too heavily on it! Judging sake solely by polishing ratio is not the best way to find your favorite sake. Each sake has a character of its own that is reflective of where it was brewed and sourced in Japan. Trying sake from different categories is a great way to expand your sake knowledge and enhance your drinking experience.


Let’s enjoy the difference in rice polishing ratio sake to understand more！ Let’s Drink, Let’s Be Friends by Nomi Tomo Sake House.