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

Significance of the Topic

Scotch Whisky is one of the world’s most traded and valued spirit drinks, yet it remains highly vulnerable to fraudulent practices and mislabeling. The authenticity and quality of whisky—including its geographical origin, maturation period and cask history—are critical for consumer protection, regulatory compliance and brand integrity. Modern non-targeted analytical strategies, combining comprehensive chemical fingerprinting with advanced chemometrics, offer powerful tools to detect counterfeits, verify production attributes and support generic as well as brand-specific authentication.

Objectives and Study Overview

The study aimed to develop and validate a novel non-targeted fingerprinting approach for the authentication and quality assessment of Scotch Whisky. Key goals included:

• Comparing two sample preparation techniques (HS-SPME vs. ethyl acetate extraction) for capturing whisky (semi)volatile profiles.
• Acquiring high-resolution chromatographic fingerprints via GC coupled to Q-TOF mass spectrometry.
• Applying unsupervised (PCA) and supervised (PLS-DA) chemometric models to distinguish whisky according to cask maturation, category (malt vs. blended) and authenticity (genuine vs. counterfeit).
• Identifying characteristic marker compounds indicative of cask history, whisky type and evidence of adulteration.

Methodology and Used Instrumentation

• Sample Set: 191 samples (71 authentic malts, 77 authentic blends, 23 malts with dual cask history, 20 known fakes) provided by the Scotch Whisky Research Institute.
• Sample Preparation: Comparison of fibre phase HS-SPME (DVB/CAR/PDMS) and liquid–liquid extraction into ethyl acetate, followed by concentration under nitrogen.
• Chromatography–Mass Spectrometry: Agilent 7890B GC with HPeINNOWax column; splitless injection; temperature program 60 °C→240 °C. Detection by Agilent 7200b Q-TOF MS (EI mode, 50–550 m/z, resolution >12 500; PCI for molecular ions).
• Data Processing: Automated deconvolution (MassHunter Unknowns), alignment and frequency filtering (Mass Profiler Professional), recursive peak integration, followed by PCA and PLS-DA (SIMCA) with VIP scoring for marker selection.

Main Results and Discussion

• Ethyl acetate extraction outperformed HS-SPME by capturing both volatile and semi-volatile compounds, yielding up to 493 deconvoluted features per sample.
• Cask Differentiation: PLS-DA separated whiskies matured solely in bourbon casks from those finished in wine-seasoned casks (sherry, port, etc.). Four markers were tentatively identified: N-(3-methylbutyl)acetamide, 5-oxooxolane-2-carboxylic acid, ethyl 5-oxoprolinate and 4-(2-hydroxyethyl)phenol, reflecting wood and wine extractives transferred during finishing.
• Malt vs. Blended: Multivariate models distinguished single malts from blended whiskies and highlighted “premium” blends approaching malt profile. Key markers for malt/premium blends included ethyl vanillate, propiovanillone and β-damascenone, while blended-specific markers were vanillin, phenylmethanol and 2,4-di-tert-butylphenol.
• Authenticity Assessment: PCA of genuine versus counterfeit samples revealed clear grouping. Genuine whiskies were characterized by higher levels of syringaldehyde, ethyl dodecanoate and 1-(3-acetylphenyl)ethanone—lignin-derived maturation compounds. Counterfeits often contained synthetic flavoring agents such as ethyl vanillin and benzaldehyde at abnormal levels.

Benefits and Practical Applications

• The non-targeted GC-Q-TOF fingerprinting approach provides a comprehensive, high-throughput method for generic and brand authentication of Scotch Whisky.
• Identified marker compounds enable the development of simplified targeted assays for routine quality control laboratories.
• Models distinguish product categories, cask maturation regimens and detect deliberate adulteration, supporting regulators, producers and customs authorities.

Future Trends and Applications

• Integration of larger sample libraries covering diverse whisky styles, cask origins and vintages to enhance model robustness.
• Coupling with isotope-ratio MS and portable spectroscopic techniques for multi-layered authentication workflows.
• Application of machine-learning algorithms to improve predictive accuracy and automate fingerprint interpretation.
• Extension of non-targeted fingerprinting to other spirit categories and fermented beverages for broader food-fraud detection.

Conclusion

The GC-Q-TOF non-targeted fingerprinting strategy, combined with multivariate chemometrics, successfully authenticated Scotch Whisky samples by cask history, product type and counterfeit status. Ethyl acetate extraction captured a comprehensive profile of (semi)volatiles, while PCA and PLS-DA models identified robust marker compounds for key quality attributes. This methodology offers laboratories a powerful platform for rapid, high-resolution screening and targeted follow-up assays, strengthening defenses against whisky adulteration and mislabeling.

Reference

Stupak, M., Goodall, I., Tomaniová, M., Pulkrábová, J., Hajšlová, J. (2018). 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, 60–70. DOI:10.1016/j.aca.2018.09.017