Analysis of Volatile Organic Compounds in Wine by Purge and Trap Concentration and Gas Chromatography/Mass Spectrometry (GC/MS)

Significance of the Topic

Volatile organic compounds (VOCs) are key determinants of wine aroma and flavor, influencing sensory descriptors such as fruity, floral or spicy notes even at trace levels. Chemical profiling of these compounds complements traditional sensory evaluation by providing objective, quantitative data to guide viticulture and enology decisions.

Objectives and Study Overview

This study aimed to develop and validate a purge-and-trap gas chromatography/mass spectrometry (GC/MS) method for the identification and quantitation of VOCs in various wine styles. A seven-point calibration was established for target analytes, and library searches were performed to tentatively identify additional compounds (TICs). A range of commercially available wines was analyzed to demonstrate method performance and compositional trends.

Methodology and Instrumentation

Analytical method based on EPA Method 8260B:

• Purge-and-Trap Concentration: OI Analytical Eclipse 4760 P&T concentrator with Tenax/Silica-gel trap, zero-grade helium purge gas, 45 °C purge and bake temperatures, 11 min purge time, 5 min bake.
• Autosampler: OI Analytical 4100 water/soil processor in soil mode to minimize foaming and water carryover.
• Chromatography: Agilent 7890A GC, Restek Rtx-VMS column (30 m × 0.25 mm ID, 1.4 µm), helium carrier at 0.8 mL/min, split 150:1, temperature program from 40 °C to 220 °C in three ramps over 15.5 min.
• Detection: Agilent 5975C MS in scan mode (35–300 amu), transfer line 240 °C, source 300 °C, quadrupole 200 °C.

Main Results and Discussion

Calibration and precision were acceptable for key analytes (e.g., ethyl acetate, isoamyl alcohol, n-propanol) with most %RSD ≤ 15%. Retention times ranged from ~4.2 min (n-propanol) to ~12.8 min (ethyl caprate). In wine samples, concentrations of esters and higher alcohols varied by style: light-bodied white wines exhibited 15–30 ppm ethyl acetate and 50–110 ppm n-propanol, while full-bodied reds reached up to 75 ppm isoamyl alcohol and 270 ppm ethyl acetate. TICs included sulfur dioxide (preservative marker) and ethyl butanoate. Ethyl acetate levels near or above its sensory threshold (90–150 mg/L) can shift aroma from fruity to solvent-like, underscoring the need for precise control.

Benefits and Practical Applications of the Method

This GC/MS approach enables:

• Objective quantitation of flavor-impacting VOCs to support quality control.
• Identification of process or varietal markers for blend formulation.
• Monitoring of sulfite levels for regulatory compliance.
• Data-driven optimization of fermentation and aging practices.

Future Trends and Potential Applications

Advances may include:

• Expansion of non-target screening libraries to uncover novel aroma compounds.
• Integration with sensory panels and chemometric models for predictive profiling.
• Miniaturized or portable purge-and-trap systems for in-field analysis.
• Automation and high-throughput platforms to accelerate vintage comparisons.

Conclusion

Purge-and-trap GC/MS is a robust, sensitive method for profiling volatile flavor and aroma compounds in wine. It delivers reproducible quantitation of esters, alcohols and other VOCs, offering winemakers actionable insights into varietal character, fermentation performance and product consistency.

Reference

1. "Where Wine Flavors Come From: the Science of Wine Aromas," WineFolly, January 2015.
2. "The Why Behind a Wine’s Bouquet," NBC News Technology & Science, February 2006.
3. "The Bottom Line on Sulfites in Wine," WineFolly, January 2014.
4. "Common Types of Wine (the Top Varieties)," WineFolly, May 2015.
5. "Wine Fault," Wikipedia, revised January 2018.
6. USEPA Method 8260B, Volatile Organic Compounds by GC/MS, Revision 2, December 1996.