Yeasts: Singularity, Fragrances And Magic

  • By
  • 14 Jan 2021
  • 5 MIN
  • Level 201
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Selected yeast ampoules - Credit : Sake Tanaka 1789 X Chartier

We could define the creation of bread, beer, wine, and sake as a unique reaction to a magical fungus. 

Described as a living organism by Louis Pasteur in his 1857 treatise Mémoire sur la fermentation alcoolique, the yeast saccharomyces cerevisiae finds its roots in the Greek 

(sugar = saccharo/fish = myces) and Latin (cerevisiae = beer).

Without this yeast placed in an anaerobic environment (oxygen-free), alcoholic fermentation (transforming sugar into alcohol) would be impossible. The latter will consume the sugar and transform it into alcohol and, at the same time, create CO2. 

During this process, other reactions take place, including the creation of esters (aromas), various acids, and other aromatic compounds (molecules) that provide the taste and aroma profile. 

This development process is controlled by temperature, among other things. Temperature influences yeasts' reaction and for sake, development is essential at around 15 °C – 18 °C. 

Therefore, it is easy to assume that yeasts are associated with the notion of terroir, i.e. the singularity of the different types of sake. Few kuras (breweries) are heated or have thermo-regulated tanks, so the climate of the prefecture and the off-season's climatic conditions will directly influence the yeasts chosen. 

Remember that the Japanese archipelago stretches from the 45th parallel to the 31st parallel, the distance between Lyon and northern Egypt, with temperature differences that can be as much as 10 °C in winter.

Yeasts can be indigenous (naturally present in the air) or selected, as in the winemaking world. With sake, most yeasts are chosen for historical reasons and reflect the philosophy of each kura.

THE SELECTED YEASTS

The National Research Institute of Brewing (NRIB) has enabled the commercialization of selected yeasts, improving the overall aroma quality of the various sake products. The goal of the research center is to harmonize sake quality and avoid possible deviations. 

Since taxes for sake production represent a significant revenue source for the government, it has made support for this industry a priority.

In 1895, Dr. Kikuji Yabe isolated the first yeasts from a moromi (a fermenting sake batch); later, the NRIB had the idea of asking the country's kuras to send in their yeasts to identify the top performer, clone it and sell it. 

In 1906, NRIB marketed its first yeast from the Sakura Masume kura in Hyogo and named it simply "Kyokai 1". Over the years, the NRIB added new yeasts to the "catalogue" and discontinued others. 

The overall trend since 1906 has been to find more aromatic yeasts that produce less acidity. 

This evolution of yeast styles reflects consumer tastes (which demand aromatic, less acidic sake) and the development of sake styles (such as the advent of daiginjo in the 1980s). 

From an aromatic point of view, the new yeasts help create two dominant molecules: ethyl caproate and isoamyl acetate; these offer very fruity aromas of melon, apple, pear and banana.

In the world of sake, the use of yeasts has been continuously evolving for more than 100 years. This evolution is not yet complete, and many research projects are still in progress. Japan is often at the forefront of research in yeast development, thanks to its many research centres and laboratories. 

This ability to evolve allows kuras to have additional resources at their disposal to mark their identity and participate in creating an inevitable (r)evolution.


For more information about natural yeast, ultra aromatic yeast and a yeast summary table click here.

Selected yeast ampoules - Credit : Sake Tanaka 1789 X Chartier