Analysis of Free Volatile Phenols in Smoke-Impacted Wines by SPME

Importance of Smoke Taint Analysis

Smoke from wildfires can lead to volatile phenols in grapes and wines that produce off flavors and compromised quality. Reliable detection of these compounds is critical for growers and winemakers to assess smoke impact and make informed harvest decisions.

Objectives and Study Overview

This study presents a solid phase microextraction gas chromatography tandem mass spectrometry method for analysis of free volatile phenols associated with smoke taint. The aim is to enable sensitive and selective quantitation of key markers such as guaiacol and 4 methylguaiacol in water and wine matrices.

Methodology and Instrumentation

• Sample preparation with NaCl saturated 10 mL wine in 20 mL headspace vial
• Agilent SPME Arrow DVB/carbon WR/PDMS fiber phase for selective extraction
• Autosampler: Agilent PAL3 with robotic tool change on 8890 GC system
• Column: Agilent J&W DB-HeavyWAX, 30 m, 0.32 mm, 0.25 μm
• MS detection on Agilent 7000D triple quadrupole using dynamic MRM mode
• Optimized headspace conditions: presorption at 250 °C, incubation 40 °C with agitation, extraction and desorption cycles

Main Results and Discussion

Method calibration in Milli-Q water and white wine showed linear ranges from low ppb to tens of ppb with R2 values above 0.995 for all targets. Salt addition increased response by 95 percent. Matrix effects were addressed using white wine as a calibration matrix, achieving R2 above 0.993 for guaiacol and methylguaiacol. In smoke impacted samples, guaiacol levels ranged from 4.7 to 10.3 ppb, with no detectable methylguaiacol in some wines. The typical guaiacol to 4 methylguaiacol ratio near 3.7/1 in smoke taint distinguishes it from oak aging.

Benefits and Practical Application

• High sensitivity with detection below 1 ppb enables early screening
• Robust quantitation in complex wine matrices with minimal matrix interference
• Automated workflow reduces solvent use and sample handling time
• Quantitative markers support harvest and blending decisions

Future Trends and Possibilities

Advances may include fiber coatings with enhanced selectivity, integration of real time sensor technologies for vineyard monitoring, and high throughput platforms for routine quality control. Coupling with data analytics could refine smoke impact thresholds and predictive models.

Conclusion

The Agilent SPME GC MS MS approach provides a sensitive, selective and automated solution for assessing smoke derived volatile phenols in wines. It supports reliable identification and quantitation of smoke taint markers, helping mitigate financial and sensory risks in wine production.

Reference

1. ETS Laboratories Smoke Impact in Grapes and Wine 2020
2. Herve E Price S Burns G Free Guaiacol and 4 Methylguaiacol as Markers of Smoke Taint in Grapes and Wines ETS Laboratories 2011
3. Abercrombie V Fast Analysis of Smoke Taint Compounds in Wine with Agilent J&W DB-HeavyWax GC Column Agilent application note 5994-0081EN 2018
4. Westland J Use of Salt to Increase Analyte Concentration in SPME Headspace Applications Agilent application note 5994-3159EN 2021
5. Westland J Response Comparison of Agilent SPME Arrows and Agilent SPME Fibers with DVB Carbon WR PDMS Phase Agilent application note 5994-3160EN 2021
6. The Australian Wine Research Institute Stubble burning a Possible Source of Smoke Taint in Grapes Fact Sheet 2021