Mixed indicator (kongo shijiyaku)

A mixed indicator is a mixture of substances that change color within specific pH ranges. When measuring the acidity of sake, a solution of bromothymol blue (BTB) and neutral red (NR) dissolved in alcohol is used. This solution serves as an indicator for evaluating the acidity of sake. The point at which it turns pale green marks the neutralization point (around pH 7.2), which makes it important for measuring acidity accurately. Mixed indicators are useful for quality control of sake and for adjustments during the brewing process.