delta C-13-Ethanol as a Potential Exclusionary Criterium for the Authentication of Scotch Whiskies in Taiwan: Normal vs. 3-Parameter Lognormal Distributions of delta C-13-Ethanol Found in Single Malt and Blended Scotch Whiskies

With the difference in the photosynthesis process between C3- and C4-plants, the C-13/C-12 stable isotope ratio of ethanol, i.e., delta C-13-ethanol, can potentially be a basis for the discrimination of Scotch whiskies derived from different raw materials. This study analyzed 51 authentic single malt Scotch whiskies and 34 authentic blended Scotch whiskies by gas chromatography-combustionisotope ratio mass spectrometry (GC-C-IRMS) and examined the resulting data by a series of fitting distribution processes. The evaluation result demonstrated that delta C-13-ethanol distribution of single malt Scotch whiskies fitted both normal and 3-parameter lognormal distribution. For blended Scotch whiskies, however, the data distribution of delta C-13-ethanol conformed with a 3-parameter lognormal distribution rather than a normal one. Moreover, 99.7% of the confidence intervals (CI) of delta(13)Cethanol for single malt Scotch whiskies would define between -23.21% to -30.07% for 3-parameter lognormal distribution, while from -11.19% to -28.93% for blended Scotch whiskies on the basis of the statistical properties. The simulative adulterated Scotch whiskies using more than 30% C4-derived edible distilled spirits can be effectively discriminated by means of CI of delta C-13-ethanol. Since the addition of rectified spirits produced from the C4 plant has been found in some cases of seized Scotch whiskies in Taiwan, establishing a CI of delta C-13-ethanol would be valuable for the purpose of Scotch whisky authentication.