The choice of yeast in sake brewing exerts marvelous leverage on the aroma and style of the final product. And, while creativity and diversity lead to better sake over time, things can indeed get out of hand. Today, there are so many different yeasts — and ways of combining them — that it almost ceases to be worth the effort to try and follow developments.
Without yeast, there is no alcohol. Yeast takes the sugars converted by the koji mold from the starches in the rice and breaks it down into alcohol and carbon dioxide. Yeast also creates an array of chemicals that give sake its body, fragrance and, to some degree, its flavor.
Over the past 100 years or so, the Japan Central Brewers’ Association has isolated these yeasts as they were discovered and made them available to breweries. The first half-dozen or so that were discovered are no longer being used, but at present there are still about a half dozen association yeasts that are commonly seen. These various yeasts are identified by number, such as Association Yeast No. 9 (kyokai kyu-go). Each has unique qualities, and inherent strengths and weaknesses.
For example, one yeast may produce a lot of flowery and fruity aromatics (such as No. 9), while another is particularly strong in fermentation at lower temperatures (such as No. 10). The amount and type of acids, too, make each one different. Brewers select the yeast based on how vigorous fermentation is (a function of rice, water and ambient temperature) as well as on the sought-after style, aroma and flavor.
Alas, gone are those simple and happy days when all we had to think about were the association yeasts. Ginjo was made with No. 9, almost everything else was No. 7. Today, almost every prefecture as well as many breweries have isolated unique sake yeasts, often for proprietary or local use. Now, beyond the 16 or so association yeasts, there are over 40 other well-known yeasts, and tons of offshoots, derivatives and proprietary yeasts. There is even sake brewed using yeasts derived from flowers!
Gone, too, are the days of simple naming. It used to be just a number. Now, there are funky names like F701, KKK-9 and ssu.
It is practically impossible to keep track of all of them, much less of the characteristics of each and the style of sake they create (at least with only seven days in a week and only one liver).
And, as if that weren’t difficult enough to follow, some brewers have begun to mix yeasts, mostly on an experimental basis for contests, but also to some degree for commercial sake. To make matters even harder to keep up with, the way the yeasts are mixed varies greatly.
Recently, I asked someone working at the Central Brewers’ Union about this mixing of yeasts. How do they do it?
“Well, some breweries mix the finished sake made with two different yeasts, some mix moto [yeast starter] made with two different yeasts, and some places just throw two pure cultures of different yeasts in at the start.”
So what you’re telling me, then, is that nobody has a clue, and everyone is just winging it, right?
The longer I write this column, the more I find the courage to be openly critical of certain aspects of the sake world. Not that I have earned that right; I have never brewed a drop of sake in my life. But still, I have to say this is a bit crazy. In the mad search for very subtle product differentiation, brewing is getting more difficult to understand.
Knowing the characteristics, pros and cons of sake yeast is interesting to a point for ordinary consumers, but after crossing a certain threshold, it calls for too much effort. For sake-drinkers, it’s best to remember just the most important yeast names and their main qualities.
For those that are interested, there is an in-depth description of many of the most important yeast strains, association or otherwise, at www.sake-world.com/html/sake-faqs.html
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Shigemasu (Fukuoka Prefecture)
Another fine Fukuoka sake. You will never go wrong with anything made by this kura. This junmai ginjo is full of contrasting flavors, with dry and spicy metamorphosing into richer, buttery notes. A moderately flowery nose with herbal and earthy tones.