In Defense of Koshu: Vintages, aging & bottle conditioning in Sake

With wine, we often hear about good vintages and bad vintages, or how long a bottle has aged. Now, there’s a new generation of brewers who are taking these ideas to sake.

For centuries, a sake brewer’s skill was said to be their ability to produce the same sake, year after year, no matter the conditions. Good rice, bad rice, wet year, dry year, you had to make a consistent taste. Aged sake, or koshu, has a reputation of being oxidative, funky or misunderstood as ‘unfresh’ sake. Regardless of your opinion of the ‘new breed’ of sake brewers and the sakes they make, there’s clearly some new things happening in the century-old world of sake:

Sake Vintages: there’s two main approaches to sake vintages – declaring the year that the sake was produced or declaring the harvest year of the rice. Since rice is harvested anywhere from September to November but brewing doesn’t usually start until November (not the top-level stuff), there is a difference between the production year and harvest year. Rice harvested in October of 2008 might not be used to brew until early 2009. What these producers are trying to do is show either the difference in rice harvest conditions of that particular year or the difference in aging potential. Some famous breweries doing this include Kuheiji, who declares the rice harvest year and also ages most of his sakes. What he’s trying to do is show the conditions of the growing season, as well as sake’s ability to age. Someone like Yamagata Masamune from Mitobe Brewery, on the other hand, bottles a particularly well made tank of their top-end Akaiwa Omachi Junmai Ginjo into a vintage ‘cuvee’.

Aging: I classify sake aging in two super broad categories, cold and warm. Aging in sub-zero temperatures is a direction we’re starting to see more and more of. It’s usually a Daiginjo, pasteurized only once (to retain the fresh, fruity flavours & aromas) and in bottle. I’ve heard anywhere from 0 to -8 degrees. This really slows down the aging process and really concentrates the flavours. I find that they are very silky on the palate as well. The sakes that are aged in warm or room temperatures are either very highly polished (Daiginjo level) or not very much (Junmai level). I think it’s safe to say that the latter is more common, as aging in warmer temperatures brings out the nutty, earthy flavours that a Junmai sake offers and is highlighted by the aging process. The fats and proteins of the rice are still there and in turn, those are the flavour components, like in the Momotose aged sakes. However, some of my favourite aged sakes are highly polished, like the Kirakucho Hizoshu, polished down to 35%. It’s clean, focused and utterly complex.

Bottle conditioning: this is done often in conjunction with the above methods. Traditionally, at classic breweries, sake was pressed –> pasteurized –> aged in tank –> pasteurized –> bottled. A lot of the new breed brewers are not tank aging or pasteurizing a second time. This can result in more characterful sake. The thought is that by only pasteurizing once, you’re leaving a lot of the flavours (ie. fruit, acidity, some effervescence) that a second pasteurization takes away. Charcoal filtering is another classic technique that removes colour and other aging agents that new breed brewers are opting out of. Why strip colour and flavour out of something you’ve spent a lot of time and effort on?

Try tasting each of these examples of aged sake and see for yourself!