Lactic acid (Nyusan)

Lactic acid is an organic acid that plays a very important role in sake brewing. It is especially important in preparing the shubo (yeast starter, also called moto), where it helps promote the pure, large-scale cultivation of yeast. The shubo is the foundation of fermentation, and the production of lactic acid within it is particularly significant. In kimoto-style shubo (kimoto-kei), lactic acid bacteria that occur naturally in the environment are taken in, and their activity produces the lactic acid. In sokujo-style shubo (sokujo-kei), by contrast, lactic acid made for brewing use is added in advance, allowing the shubo to be started up in a short time. In the early stages of the moromi (fermentation mash), when the risk of contamination is high, lactic acid prevents spoilage bacteria from multiplying and provides an environment in which yeast can multiply smoothly and carry fermentation forward. It is also one of the most abundant organic acids in sake, and together with succinic acid it is an important component. In this way, lactic acid is an indispensable element in maintaining the quality of sake.