酒質を決める酵母と酛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.