Bacterial acidity (saikin sando)

Bacterial acidity (saikin sando) is an indicator that measures the level of contamination by acid-producing bacteria during the sake brewing process. Samples are taken from materials such as water, koji, shubo (yeast starter), and moromi (fermentation mash), and are cultured under specific conditions to encourage the growth of acid-producing bacteria. The cultured liquid is then titrated with a one-tenth dilution of sodium hydroxide solution, and the bacterial acidity is calculated from the amount required for the titration. In general, a bacterial acidity of 1 ml or less for brewing water, koji, shubo, and moromi is considered normal, while a value of 2 ml or more suggests possible contamination by acid-producing bacteria. Managing this indicator is important for maintaining the quality of sake and for producing safe, delicious sake.