Yeast density (koubo mitsudo)

Yeast density refers to the number of yeast cells contained in 1 g or 1 ml of shubo (yeast starter) or moromi (fermentation mash). Yeast plays a key role in sake fermentation, producing alcohol and aroma compounds. A high yeast density means more active fermentation and can affect the character of the sake, so it is an important indicator that is measured regularly during brewing. By adjusting yeast density, brewers can control the taste and flavor of the finished sake.