A novel approach to assess the quality and authenticity of Scotch Whisky based on gas chromatography coupled to high resolution mass spectrometry

Importance of the topic

Scotch Whisky is one of the most valuable spirits worldwide and is vulnerable to counterfeiting and adulteration. Authenticity controls are essential to protect brand reputation, ensure consumer safety and maintain regulatory compliance. The oak cask maturation process greatly influences whisky quality, making chemical fingerprinting of volatile and semi-volatile components a powerful tool for authenticity and quality assessment.

Objectives and overview of the study

This study aimed to develop a non-targeted fingerprinting strategy using gas chromatography–high resolution mass spectrometry (GC-HRMS) combined with chemometric analysis to:

• Differentiate Scotch Whisky maturation histories (cask types).
• Discriminate between malt and blended whiskies.
• Identify markers of genuine products and detect counterfeit samples.

Methodology and instrumentation

• Samples: 171 authentic Scotch Whiskies (malt, blended; bourbon and wine cask history) and 20 pre-identified counterfeit spirits provided by the Scotch Whisky Research Institute.
• Sample preparation: comparison of headspace solid-phase microextraction (SPME) with DVB/CAR/PDMS fiber and ethyl acetate liquid–liquid extraction with formic acid and NaCl salting.
• Chromatography–MS: Agilent 7200b GC-Q-TOF system with INNOWax column; electron ionization and positive chemical ionization modes; retention-time locking.
• Data processing: spectral deconvolution, peak alignment, normalization, and multivariate analysis (PCA, PLS-DA) to select discriminant markers.

Main results and discussion

• Ethyl acetate extraction enabled detection of ~493 compounds (after deconvolution) versus ~260 by SPME, improving coverage of semi-volatile markers.
• Cask maturation: PLS-DA separated whiskies matured solely in bourbon casks from those finished in wine casks (sherry, port, red or white wine). Key markers in bourbon-plus-wine casks included:

• N-(3-methylbutyl)acetamide
• 5-oxooxolane-2-carboxylic acid
• Ethyl 5-oxoprolinate
• 4-(2-hydroxyethyl)phenol

• Malt versus blended whiskies: PCA and PLS-DA distinguished malts (including peated Islay styles) from blends. Markers for malt and premium blends were:

• β-damascenone
• Ethyl 4-hydroxy-3-methoxybenzoate
• 1-propanone-1-(4-hydroxy-3-methoxyphenyl) (“propivanillone”)

Markers enriched in blends included:

• Vanillin
• Phenylmethanol
• 2,4-di-tert-butylphenol

• Counterfeit detection: PCA separated fake from genuine samples. Genuine markers such as syringaldehyde, ethyl dodecanoate and 1-(3-acetylphenyl)ethanone were absent or at low levels in fakes. Fakes often contained added aroma agents (e.g., ethyl vanillin, benzaldehyde) at abnormal levels.

Benefits and practical applications of the method

• Comprehensive non-targeted fingerprinting captures known and unknown markers of authenticity.
• High-resolution deconvolution resolves co-eluted analytes and improves compound coverage.
• Chemometric models enable rapid screening of cask history, whisky style and detection of counterfeits.
• Approach can be integrated into QA/QC and regulatory workflows for routine authenticity checks.

Future trends and applications

Advances in spectral databases and machine learning will enhance marker discovery and model robustness. Miniaturized or portable high-resolution MS systems and integration with isotope ratio analysis could allow on-site authentication. The methodology can be extended to other spirits and food products, and targeted quantitation of identified markers may support regulatory limits and labeling requirements.

Conclusion

The non-targeted GC-Q-TOF fingerprinting combined with multivariate analysis provides a robust strategy for assessing Scotch Whisky authenticity and quality. It enables discrimination of cask maturation, whisky style and identification of both genuine markers and counterfeit indicators, offering an effective tool for industry and regulatory control.

References

• Stupak M, Goodall I, Tomaniova M, Pulkrabova J, Hajslova J. A novel approach to assess the quality and authenticity of Scotch Whisky based on gas chromatography coupled to high resolution mass spectrometry. Analytica Chimica Acta. 1042 (2018) 60–70.