Determination of Amino Acidity in Japanese Sake Based on the Voltammetric Measurement of Surplus Acid by Quinone Reduction (Supporting Information)

In this paper, we propose voltammetry for determining amino acidity in Japanese sake. The measurement principle of this voltammetric method is based on a concept of acid-base back titration and a decrease of cathodic prepeak current of 3,5-di-tert-butyl-1,2-benzoquinone (DBBQ) caused by surplus HCl, which is obtained by the neutralization between excess HCl and amino acids in Japanese sake. In the comparisons of amino acidities in Japanese sakes (n = 10) obtained by this voltammetric method and the official titration, called the ethanol additional method, the correlation coefficient (r) was 0.946, indicating that the amino acidities in Japanese sakes by both methods were essentially the same.