Sake’s main ingredient is rice but before it is fermented it goes through a process of polishing and the brewer has the option of what level of polishing to work with. This is shown on the bottle as a percentage known as the rice polishing ratio or the seimaibuai 精米歩合. There are brewers who work with completely unpolished rice or brown rice; this is very rare and most choose to work with rice that has been polished. 

Traditional mills could only polish to around 90% remaining and most probably had a fuller body with more body, acidity and structure. The introduction of the vertical polishing machine Seimaiki 精米機 back in 1933, initially limited to competition sake, allowed brewers to work with polished rice well beyond the 90% remaining. This advancement in technology led to the birth of highly polished sake as well as new terminology for categorizing sake.

But why polish? Shaving off the outer portion of the rice removes proteins, fats, vitamins, lipids, the impurities if you will, leaving the starchy centre (the shinpaku 心拍) and also reduce the risk of off-flavours too.

Although limiting in its nature, the rice polishing ratio can give us a indication of the style of sake. Many brewers who work with highly polished rice (60% or less) aim for a lighter, aromatic style. 

But what happens when you start polishing to beyond 50% rice polishing ratio.

If the brewer aims for an aromatic style, fermenting at low temperatures, the style will be an extreme version of the above and since it’s a relatively new category and style of sake, many choose to brew this way.

A well-known sake brewery in Yamaguchi prefecture turned around a faltering company back in 1992 by brewing sake with a never-achieved 23% polishing ratio remaining. The idea was to produce a refined sake to appeal to discerning consumers in Tokyo and saw their sales grow both domestically and internationally with their sake on the menus of some top restaurants in Paris and New York.

So your next question is, do they still hold the record for sake using the most highly polished rice? The answer is a resounding NO.

Last year a brewery in Yamagata prefecture achieved 1% polishing ratio remaining with 99% of the rice NOT going into the tank to be fermented. For the never-achieved feat with the Yamagata Dewasansan rice variety, it took 1800 hours, around 2.5 months. “Komyo” meaning Zenith in English, went on sale on October 1st, 2017 priced at around $1000 for a 720ml bottle.

With only 150 bottles produced, I will never have the chance to try it but I can pretty much guess that it will be all about delicate aroma with very little flavour; not my kind of thing.

Judging by the price of highly polished sake, you would think that they are superior in quality. Is Junmai Daiginjo really better than Junmai like everyone keeps saying?

Contrary to popular belief, the lower the ratio does not equate to higher quality sake, it’s simply one tool of many available to brewers and an indication of the style. Junmai is premium sake just like Junmai Daiginjo.

But why are they so expensive?

One of the main reasons for high prices of these top tiers is that you simply need more rice since more is shaved away. Also, brewers often choose to work with more expensive sake-specific rice types known as sakamai 酒米. Other reasons include a very careful brewing approach from soaking the rice timed down to the second, colder fermentation temperatures to stress the yeast and bring out those Ginjo-ka 吟醸香 (think fruity and floral aromas), a longer fermentation period and slower and more time-consuming fukuro-shibori 袋搾りdrip pressing and well maybe marketing.  

So concluding, 1% is the lowest you can go with rice polishing and I don’t think anyone is going to beat that record; 0.5% just doesn’t have the same ring to it. And yes there can be more work involved in producing a highly polished sake with that low percentage that enthusiasts look for but it does not necessarily translate to flavour and quality per se. So just keep in mind that the rice polishing ratio and its associated categorisation has its limits. 

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