Application of gas chromatography-combustion-stable isotope mass spectrometry in the identification of exogenous alcohol in whisky

Using 129 whiskies from different regions such as Scotland, Ireland, America and Japan as research samples, the differences in carbon stable isotope ratios (δ¹³C) of isobutanol, n-propanol, amyl alcohol, ethyl acetate, acetaldehyde and ethanol among the volatile flavor components was detected, and a method for the identification of exogenous alcohol in whiskey was established by gas chromatography-combustion-stable isotope mass spectrometry (GC-C-IRMS). Results showed that the δ¹³C of ethanol in Scottish single malt whisky ranged from -27.84‰ to -25.04‰, the δ¹³C of ethanol in Scottish blended whisky ranged from -28.21‰ to -20.72‰, the δ¹³C of ethanol in whisky containing corn raw material ranged from -26.66‰ to -12.83‰, the δ¹³C of ethanol in whisky without corn raw material ranged from -28.86‰ to -24.04‰. Based on the fitted linear intercept deviation range (2SD) to discriminating adulteration, the δ¹³C of ethanol showed good linear relationship with that of n-propanol, isobutanol and acetaldehyde in whisky. The correlation coefficients (R²) was 0.876, 0.832, and 0.868, respectively. By combining the linear intercept deviation range with the δ¹³C distribution range of ethanol, the identification of whisky exogenous alcohol is more sensitive.