- Association Yeast No. 7 (Kyōkai No. 7)
Isolated at the Miyasaka Brewing Company, Ltd in Nagano Prefecture in 1946, and also known as Masumi Yeast. Like No. 6 yeast, it stains red in the TTC test. Large colonies have a depression in the centre and rough radiating wrinkles. Sugar consumption is weaker than No. 6, but with splendid aromatics and strong ginjo-ka. It has characteristics in line with bottom fermenting yeasts (relatively weak respiration, strong fermentation, somewhat weak membrane formation), and is the most widely used yeast today.
When propagated in an inorganic nitrogen medium at 35℃ it has an absolute requirement for pantothenic acid, which cannot be replaced by beta-alanine as a substitute (unlike other sake yeasts under the same conditions). If propagated at below 25℃, growth in a beta-alanine medium is possible, so it is possible to distinguish No.7 from other sake yeasts (primarily No. 6) and to measure the level of purity of No. 7.