Statistical Differentiation of Tequila Spirits Using ® SPME-GCxGC-TOFMS and ChromaTOF Tile Software

Význam tématu

Tequila is a commercially and culturally important distilled spirit whose sensory profile is determined by a complex volatile fraction. Robust characterization of tequila aroma is essential for product authentication, quality control, production optimization and understanding the impact of raw materials, terroir and aging. Comprehensive two‑dimensional gas chromatography coupled to time‑of‑flight mass spectrometry (GCxGC‑TOFMS) combined with headspace solid‑phase microextraction (HS‑SPME) addresses challenges of complex volatile matrices by increasing chromatographic peak capacity, improving deconvolution and enabling more confident identification of low‑level aroma markers.

Cíle a přehled studie / článku

This application study evaluated a workflow to differentiate ten commercial 100% agave tequila samples (various brands, regions and aging classes) using HS‑SPME sampling, GCxGC‑TOFMS analysis on a Pegasus® BT 4D and multivariate/statistical processing with ChromaTOF Tile software. Goals were to (1) maximize annotation of aroma compounds, (2) demonstrate the resolving power of GCxGC in separating coeluting species, and (3) identify chemical features and multivariate patterns (PCA) that discriminate samples by geography and aging.

Použitá metodika a instrumentace

Sample handling and analysis:

• Ten commercial 100% agave tequilas, sampled in triplicate.
• Aliquot: 250 µL per sample placed into 20 mL headspace vials for HS‑SPME extraction.
• SPME: headspace SPME Arrow sampling (incubation, extraction and desorption parameters optimized—see original note for exact timings and temperature conditions).
• Calibration/RI: n‑alkane standard C7–C30 analyzed to calculate linear retention indices.

Instrumental platform:

• GCxGC‑TOFMS: LECO Pegasus BT 4D comprehensive two‑dimensional GC coupled to time‑of‑flight MS, offering high acquisition speed and non‑skewed spectra for effective deconvolution and library matching.
• Data processing: ChromaTOF Tile software for tile‑based GCxGC alignment, feature detection, library (NIST) and retention index matching, F‑ratio comparisons, and multivariate analysis (PCA).

Hlavní výsledky a diskuse

Annotation and separation:

• Over 170 compounds were annotated in a representative blanco sample using thresholds of similarity ≥800, S/N >10 and ΔRI ≤10, demonstrating high identification coverage for a complex matrix.
• GCxGC dramatically improved separation of coeluting analytes that would overlap in 1‑D GC; for example, phenol and 1‑octen‑3‑ol shared first‑dimension retention but were resolved in the second dimension, with strong spectral matches (phenol 924/1000; 1‑octen‑3‑ol 884/1000).

Chromatographic class structure and interpretability:

• GCxGC contour plots showed structured elution patterns enabling visual class separation: aromatics and cyclo‑oxygenated compounds, monoterpenes, alcohols and esters occupied distinct regions—facilitating rapid interpretation of sample composition and chemical families contributing to aroma.

Statistical differentiation and markers:

• Data were processed with ChromaTOF Tile using an F‑ratio comparison to highlight discriminating features. Filtering excluded features with F‑ratio <75, spectral similarity <750 and column/fiber bleed.
• After filtering, 40 chemical features were selected for PCA. The first two principal components accounted for 57.71% of the variance.
• PCA revealed clear geographical clustering: samples from Jalisco grouped with positive PC1 values and were characterized by terpenoid markers (e.g., 1‑methyl‑4‑(1‑methylethenyl)cyclohexanol, α‑terpineol, 7‑octen‑2‑ol) associated with floral/herbal notes.
• Guanajuato samples (PC1 < 0) split into subgroups: one enriched in linear esters (propyl propanoate, 3‑methylbutyl esters, heptanoic acid esters) imparting tropical/banana‑like aromas; another subgroup (including an añejo) showed aging markers such as furfural, furans and oxygenated esters (woody, buttery, tobacco, fruity notes).

Workflow efficiency:

• End‑to‑end processing from raw GCxGC‑TOFMS data to statistical interpretation using ChromaTOF Tile required approximately 60–90 minutes for the described dataset, with actual times depending on sample count, method complexity and hardware.

Přínosy a praktické využití metody

The combined HS‑SPME GCxGC‑TOFMS and tile‑based data processing workflow delivers practical benefits for the beverage and flavor industries:

• Enhanced resolution and sensitivity allow reliable detection and identification of trace aroma compounds and coeluting species that are critical for sensory quality and authenticity.
• Structured chromatograms simplify class‑based interpretation and accelerate marker discovery for geographic origin, production process or aging.
• Fast, automated tile‑based comparison and PCA streamline routine screening, quality control, product development and reformulation efforts.

Budoucí trendy a možnosti využití

Potential developments and applications include:

• Scaling the approach to larger sample collections for robust fingerprint libraries and routine authentication workflows.
• Integration of machine learning and supervised classification models to translate chemical features into predictive origin or quality labels.
• Expansion of high‑quality spectral and RI libraries for improved automated identifications, including curated tequila‑specific entries.
• Adapting similar GCxGC‑TOFMS + tile workflows for other distilled beverages and complex flavor matrices; coupling with sensory panels to link chemical markers with perceived aroma.
• Further automation of sampling and processing to enable higher throughput QC laboratories to adopt comprehensive volatile profiling.

Závěr

This study demonstrates that HS‑SPME combined with GCxGC‑TOFMS on the Pegasus BT 4D, analyzed with ChromaTOF Tile, provides a rapid, high‑resolution analytical workflow for tequila aroma profiling. The platform resolved coelutions, annotated dozens to hundreds of volatile compounds, and—through multivariate analysis—identified geographical and aging‑related chemical markers. The methodology is directly applicable to authentication, quality control and flavor research in the beverage industry.

Reference

1. Huang X., Cadwallader K. R. A Critical Review of the Flavor Chemistry of Tequila. In: Chemistry of Alcoholic Beverages; 2023.
2. Peña‑Álvarez A., Capella S., Juárez R., Labastida C. Determination of terpenes in tequila by solid phase microextraction‑gas chromatography–mass spectrometry. Journal of Chromatography A. 2006;1134:291–297.
3. The Good Scents Company. Database of fragrance and flavor compound information.