Wild yeast (yasei kobo)

Wild yeast (yasei kobo) refers to yeast that occurs naturally in the sake brewing process. These yeasts are not necessarily desirable in sake making. Particularly when using traditional shubo (yeast starter) methods such as kimoto and yamahai, it is important to cultivate a specific species of yeast. Because wild yeast is influenced by microorganisms originating from the brewing environment and the brewing water, it is often difficult to control and may harm the soundness of the sake's quality during fermentation. In particular, environmental conditions created by lactic acid bacteria and nitrate-reducing bacteria living in the brewery environment can make it difficult for wild yeast to survive. For this reason, sake brewing generally uses intentionally selected yeast, which is especially important when consistent quality is required.