What is "brewery yeast"?

In the sake brewing process, yeast breaks down sugar in the yeast starter and mash to produce alcohol (fermentation). Nowadays, purely cultured yeast is generally added, but in the past, brewing was done with wild yeast that floated in nature. This yeast was called "kuratsuki yeast" (brewery yeast), meaning yeast that lived in the brewery, and is thought to grow by attaching to the beams and walls of the brewery. However, natural yeast is unstable, so there was constant concern about spoilage.

The birth of "Kyokai Yeast"

So in the early 1900s, "Kyokai yeast" was developed. In 37, the Brewing Research Institute was established by the Ministry of Finance, and research into sake brewing was promoted. As a result, a high-quality yeast was collected and isolated from the Sakura Masamune brewery in Nada in 1904, and became the first Kyokai yeast. Currently, the yeasts used in many breweries are Kyokai No. 1906 (from Aramasa, Akita Prefecture), Kyokai No. 1 (from Masumi, Nagano Prefecture), and Kyokai No. 6 (from Koro, Sake Brewing Research Institute, Kumamoto Prefecture). It is cultivated in pure culture by the Brewing Society of Japan, a public interest incorporated foundation, and distributed in ampoules and powder form only to breweries with sake brewing licenses.

Each Kyokai yeast has its own characteristics: No. 6 has strong fermentation power and a mild aroma, No. 7 has a clean, delicate ginjo aroma, and No. 9 has a gorgeous ginjo aroma and tends to have less acidity.

There is a movement to reconsider the brewery yeast that creates unique characteristics

The widespread use of Kyokai yeast has enabled all sake breweries to produce a stable supply of sake. Furthermore, depending on the choice of yeast, it is possible to produce sake with the desired taste and aroma to a certain extent. However, on the flip side, this can weaken the individuality of each brewery, and we may end up with a situation where all the sake produced is delicious but similar in taste.

Thinking that this was not interesting, some breweries reconsidered their roots and started brewing using only their own yeast, without adding any yeast. Recently, an increasing number of breweries are isolating and cultivating their own yeast for use in their sake. In the case of one brewery whose building was washed away by the tsunami during the Great East Japan Earthquake, they were able to resume the same sake brewing practices in their new location thanks to having entrusted their own yeast to a research institute. Stories like this show that brewery yeast is what gives a brewery its uniqueness, and is part of its identity.

Writer/Sake Master Eriko Fujita
Expand your world to a sake specialty store in Osaka and encounter a variety of sake and sake breweries. Favorite sakes are Akishika, Ohgi, and others.
Other than drinking, my hobbies include collecting minerals and raising swallowtail butterflies.