Magic of the Sake Yeast

日本酒造りにおける「酵母」の魔法

Sake酒= Rice米 +Water水+Koji麹+Yeast酵母+Lactic Acid乳酸菌 (Although not always)

The only simple thing about how sake is made is perhaps the few ingredients it requires.

Why is yeast necessary?

Koji makes sugar from rice starch and yeast eats the sugar and churns out alcohol.

In the finished product, Yeast imparts mainly the aromas which are prominent in Sake. Sure, they also can affect the flavour but most of their work shows in the way the sake smells.

Once upon a time, Sake was made with just Rice, Water and Koji (A moldy rice, don’t worry, we’ll explain more next time).

At that time, yeast just fell into the fermenting vats from the air and microbiology did its thing with the help of some human brawn and brains.

As fermentation technology advanced, people realized that they could isolate the yeast strains which hung around the breweries waiting for a pot of rice, water and koji to get cozy with.

Researchers isolated the first strain of sake yeast in 1898. They continued to discover new strains from then on and soon yeast were bottled in liquid form and distributed by The Brewing Society of Japan, 日本醸造協会.

This made the process of brewing a much more consistent and controlled practice, leading to most brewers abandoning the traditional way of working with the ambient yeasts that hung in the rafters of their brewery.

Why does the search for new sake yeast continue?

Because yeasts primarily drive the aroma of the brew and the aroma is what makes the first impression. Especially when it comes to Sake appraisal competitions, those which are working with new and not commonly recognized aromas, tend to stand out more and win more medals.

But beyond contests, a very essential component to our enjoyment of sake is the wide range of fruity aromas we can enjoy while imbibing. For this we can thank the tireless research and development of sake yeast varieties.