Compound Specific Carbon Isotope Analysis in Sake by LC/IRMS and Brewers' Alcohol

Sake is a traditional Japanese alcohol. Nowadays, the consumption for Sake is increasing in worldwide and its popularity is growing. However, there are act of fraudulence by additional brewers' alcohol and sugar. Therefore, a method is needed to find illegal fraud on label. In this work, we analyzed the delta C-13 values of the ethanol (delta C-13(eth)) and glucose (delta C-13(glu)) in Sake by liquid chromatography combined with isotope ratio mass spectrometry for the first time. Further, we developed the criteria using delta C-13(eth) and delta C-13(glu) to check brewers' alcohol and sugar. In addition, there are some sake categories (Ginjyo and Futsu-shu) allowed to additional brewers' alcohol up to legally determined percentage. The experimental additions of brewers' alcohol from a C4 plant were conducted to Junmai, as sake by C3 plants. There was a strong correlation (R = 0.98, P < 0.05) between the percentage of added brewers' alcohol and the delta C-13 values. We developed the method using the relationship for calculating percentage of brewers' alcohol for the first time and estimated the percentage for commercial sake. Further, the price of sake was found to be inversely related to the percentage of brewers' alcohol in the sake.