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Jan 24, 2023

HOW TOHow Rice Polishing Rate Leads More Refined Sake

All rice must be polished before brewing into sake, but the amount removed first – often called the polishing or milling rate – helps create a diverse flavor profile that rewards exploration.

Jan 24, 2023

How rice becomes sake in the first place

If you’ve ever tried a fruity sake, you might wonder how simple rice can result in a flavor profile so different from what rice actually tastes like. Brewing sake is a complex process that starts with whole grain rice and ends with an alcoholic beverage, and the simple terms below describe the process in general.

Rice is harvested, dried and polished to remove the husk and some outer layers. Then, it’s washed, soaked and steamed. Part of the rice is sprinkled with Aspergillus oryzae mold spores to make rice koji, while some is held back for the main fermentation. When the rice koji is ready, it is mixed with water, steamed rice and yeast, and the fermentation  process can begin.

The magic of koji

Rice koji is really the heart of sake brewing. The mold makes enzymes to convert starch into sugar for the yeast to make into alcohol. Without it, sake wouldn’t exist. Although this is koji’s most important job, it isn’t the only one. Some koji enzymes also digest proteins and fats, which results in many complex flavor profiles. This is where the impact of rice polishing is most prevalent.

Beneath the husk, rice grains have a layer of fats and proteins around a core of pure starch. More polishing removes more of that layer, exposing more starch. The polishing rate can dramatically influence the sake’s taste because the koji enzymes will create less complex flavor profiles, resulting in a cleaner, more refined sake. 

The power of numbers – what does “daiginjo” mean, anyway?

When you buy a premium sake with a class name like junmai or ginjo, Japanese law requires the polishing rate on the label. This will be marked as a percentage, usually 70% or lower, and represents the amount of the original rice grain left after polishing. So, a polishing rate of 70% means that 30% of the grain is gone.

The ginjo and daiginjo classes are essentially defined by their polishing rates. To be a ginjo class sake, the rate must be 60% or lower, and for daiginjo it must be 50% or lower. These are upper limits, so you might see both classes with lower numbers, like a 55% ginjo or 35% daiginjo, as brewers adjust their refinement.

Wax on, wax off: the nuanced world of rice polishing 

As mentioned, removing more of the rice creates more refined sake, with less of the complex flavors from the proteins and fats. Daiginjo, in particular, is known for crystal clear flavors that don’t interfere with its signature fruity aromas.

To see for yourself how polishing influences sake, find a range of sake from a given brewery for a taste test. Be sure to choose the same rice variety and take note of the polishing rates to see the change in flavor and aroma.

The brand Dassai is almost tailor-made for this, since all Dassai is junmai daiginjo made from Yamadanishiki rice with three different polishing rates: 45%, 39% and 23%. A quick sip will show just how much impact the simple act of polishing has on sake flavor.