On making the Japanese traditional spirits
Shochu, the pitching is commonly carried out by the addition of a volume of about 0.6% of fermenting mash. The re-pitching procedure is called“
Sashimoto”. By the repetition of
Sashimoto, the wild yeasts which invade the
Shochu mash multiply and become dominant because the growth rates of most wild yeasts are faster than that of pure
Shochu -yeast. Consequently, this brings about a decreased purity of
Shochu -yeasts and undesirable quality for the resulting
Shochu.
We studied the changes in the purity of
Shochu-yeast S4 during repeating
Sashimoto and evaluated the qualities of resulting
Shochu. Since S4 yeast is a cerulenin tolerant and ethyl caproate high producing strain while most wild yeasts are cerulenin sensitive strains, we confirmed that changes in S4 purity during the repeating
Sashimoto were possible by detecting its cerulenin tolerance as the yeast purity index.
We also confirmed that, in conditions of the wild yeast, the specific growth rate is from 1.2 to 2.4 times faster than that of
Shochu-yeast, and it was necessary to keep yeast purity higher than 50% to maintain a high ethyl caproate content.
A cerulenin sensitive wild yeast(WS1)isolated from the
Shochu mash in this study was identified as
Saccharomyces cerevisiae by its physical properties and the homologous analysis of the ITS domain.
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