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Yeast and Moto Controlling Sake Quality

What makes the most powerful impact on sake quality, such as aromas, tastes and flavor, is yeast. There are Kyokai (or Association) yeast No.6 (also known as Aramasa Yeast), Kyokai (Association) Yeast No.7 (also known as Masumi Yeast), and Kyokai (Association) yeast No.9 (also known as Kumamoto Yeast), and others. The names of yeast show a broad outline of sake properties. However, this system started from around Meiji period (1868-1912) i n Japan. Before that, people just had to rely on the function of microorganisms called ie-tsuki-kobo (literally, house yeast), which float in the environment of breweries.
To resolve such instability, breweries started to share yeast collected from moromi of sake, from time to time, at the National New Sake Awards sake contest. Now, the yeast is grown and distributed by the Brewing Society of Japan and it is called Kyokai (or Association) Yeast.
The yeast, rice koji made from koji mold, local water and steamed rice are used to make shubo (or moto) by growing large amounts of yeast to activate moromi fermentation. After this shubo is made, then the shikomi process starts. Shubo is literally the “mother of sake”. A good mother is important for growing a child and making sake.