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Sake's Flavor Wizard: Exploring the Magic of Yeast


When savoring sake, various elements come to mind: rice variety, polishing ratio, the brewer's skill, and more. Yet another crucial factor that significantly influences the flavor of sake is the enigmatic yeast.


<reference: 東京大学微生物研究室 >

What is Yeast?

Yeast, scientifically known as "S. cerevisiae," is a type of fungus. It's used in the fermentation of various alcoholic beverages, including sake, wine, and beer. Yeast breaks down sugars, transforming them into alcohol and carbon dioxide. In sake brewing, this magical ingredient is called "seishu kobo" (清酒酵母), and its role goes beyond mere alcohol production.


Yeast's Impact on Sake Flavor

In addition to alcohol, yeast generates a myriad of compounds, including aroma components and acids. These elements intricately intertwine, crafting the unique flavors found in sake.

  • Aroma Components

Two key aroma components that define sake's fragrance are:

  • Isoamyl acetate: reminiscent of melon or banana, imparting a fruity aroma

  • Ethyl caproate: reminiscent of strawberry or apple, contributing a sweet aroma

The ratio of these components greatly influences the overall aroma. For instance, a higher concentration of isoamyl acetate yields a more vibrant aroma, while ethyl caproate emphasizes sweetness.

  • Acids

Acids produced by yeast also play a crucial role in shaping sake's taste. Two notable acids are:

  • Malic acid: provides refreshing acidity

  • Succinic acid: imparts umami

Malic acid provides a pleasant tartness to sweet sake, balancing the flavors. On the other hand, succinic acid contributes an umami savor, enriching the complexity of the taste profile.


<reference: 月桂冠株式会社 >

Types of Yeast

A diverse range of yeasts are employed in sake brewing, each possessing distinct characteristics. Here's an overview of some key types:

  • Kyōkai Yeast

Distributed by the Japan Society of Brewing, Kyōkai yeast (協会酵母) is widely used by breweries. It ensures stable quality and fermentation, making it a cornerstone of sake brewing. Notable types include:

  • No. 6 Yeast: clean and dry

  • No. 7 Yeast: mild aroma

  • No. 9 Yeast: floral aroma

  • Prefectural Yeasts

These yeasts are developed and distributed by each prefecture's research institute. They often adapt to local rice varieties and terroir, yielding unique flavors.

  • Flower Yeast

Developed by Tokyo University of Agriculture, flower yeast (花酵母) is cultivated from flowers. It imparts a floral aroma and distinctive taste.

  • Wine Yeast

Traditionally used in winemaking, wine yeast (ワイン酵母) has recently found its way into sake brewing. It creates a taste profile akin to wine, with pronounced acidity and lingering notes.

  • 蔵付き酵母 (Kura-tsuki Yeast)

Residing in a specific brewery for generations, kura-tsuki yeast (蔵付き酵母) shapes the brewery's signature flavor. It holds the potential to produce highly個性的な日本酒.


Conclusion

Yeast acts as a magical wizard, orchestrating the flavors of sake. By utilizing various yeast strains, breweries craft a diverse range of unique expressions. So, the next time you sip on sake, take a moment to appreciate the wondrous work of yeast.

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