Analysis of Scotch Whisky by 1H NMR and chemometrics yields insight into its complex chemistry

Abstract

Scotch Whisky has been analysed as a complex mixture in its raw form using high resolution Nuclear Magnetic Resonance (NMR) and previously developed water and ethanol suppression techniques. This has allowed for the positive identification of 25 compounds in Scotch Whisky by means of comparison to reference standards, spike-in experiments, and advanced 1D and 2D NMR experiments. Quantification of compounds was hindered by signal overlap, though peak alignment strategies were largely successful. Statistical total correlation spectroscopy (STOCSY) yielded information on signals arising from the same compound or compounds of similar origin. Statistical analysis of the spectra was performed using Independent and Principal Components Analysis (ICA, PCA) as well as Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA). Several whisky production parameters were successfully modelled, including blend or malt status, use of peated malt, alcohol strength, generic authentication and maturation wood type, whilst age and geographical origin could not be modelled.

Keywords: 2-Methylbutanol (PubChem CID: 8723); 2-Phenylethanol (PubChem CID: 6054); 3-Methylbutanol (PubChem CID: 31260); 5-HMF (PubChem CID: 237332); Acetaldehyde (PubChem CID: 177); Beverages; Chemometrics; Complex mixtures; Ethanol (PubChem CID: 702); Ethyl acetate (PubChem CID: 8857); Ethyl formate (PubChem CID: 8025); Formic acid (PubChem CID: 284); Fructose (PubChem CID: 5984); Furfural (PubChem CID: 7362); Gallic acid (PubChem CID: 370); Glucose (PubChem CID: 5793); Isobutanol (PubChem CID: 6560); NMR; Scotch Whisky; Syringaldehyde (PubChem CID: 8655); Syringic acid (PubChem CID: 10742); n-Butanol (PubChem CID: 263); n-Propanol (PubChem CID: 1031).