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

<p>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-<i>tert</i>-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 (<i>n</i> = 10) obtained by this voltammetric method and the official titration, called the ethanol additional method, the correlation coefficient (<i>r</i>) was 0.946, indicating that the amino acidities in Japanese sakes by both methods were essentially the same.</p>