Solid Phase Micro-Extraction (SPME) Coupled with Selectable 1D/2D GC-MS for the Determination of Food Product Flavors

Significance of the Topic

The accurate detection of trace flavor and fragrance compounds in complex food products is essential for ensuring quality, safety, and consistency in food production. Traditional one-dimensional separations often lack the peak capacity needed for unambiguous compound identification, especially at low concentrations.

Objectives and Study Overview

This study demonstrates a selectable one-dimensional/two-dimensional GC-MS configuration combined with solid phase micro-extraction (SPME) and parallel olfactory detection. The goal is to enhance resolution and sensitivity for flavor compound analysis in various food matrices, including potato chips and poultry seasoning.

Methodology and Used Instrumentation

Sample Introduction and Extraction:

• SPME fiber (DVB-Carboxen-PDMS) for solvent-free headspace extraction at 65 °C for 20 min.
• Automated sample handling with a 32-position tray and agitation at 250 rpm.

GC-MS Configuration:

• Agilent 6890 GC with low thermal mass (LTM) column modules.
• First Dimension: 30 m Rtx-5Sil MS (0.25 mm × 0.25 µm).
• Second Dimension: 30 m DB-Wax (0.25 mm × 0.5 µm) or chiral column for isomer separation.
• Gerstel CIS 4 PTV inlet, MPS 2 autosampler with SPME option, and ODP 2 olfactory detection port.
• Agilent 5975C inert XL MSD with full-scan acquisition (40–350 amu).

Main Results and Discussion

• Potato Chips: Comparison of fresh and heat-stressed chip headspace revealed increased aldehyde levels (pentanal, hexanal, nonadienal, nonanoic acid) in rancid samples. Brand comparisons showed higher acetone and hexanal in less fresh products.
• Flavored Chips: Sour cream & onion chips exhibited methoxy-propoxypropanols likely from packaging. Salt & vinegar chips were dominated by acetic acid. Barbecue chips displayed a complex terpene profile. Two-dimensional separation via heartcuts resolved overlapping peaks, allowing identification of odor-active pyrazines (dimethylpyrazines, ethylmethylpyrazine, trimethylpyrazine) responsible for roasted and baked potato notes.
• Poultry Seasoning: Headspace SPME of a mix containing thyme, sage, marjoram, rosemary, black pepper, and nutmeg produced a complex 1D chromatogram. Heartcutting to the second dimension separated camphor, thymol, borneol, eucalyptol, thujone, isoledene, and ylangene, each with distinct woody or floral olfactory descriptors. Repeated injections demonstrated high retention time reproducibility.
• Chiral Isomer Analysis: A standard of 3,3,5-trimethyl-2-cyclohexen-1-ol yielded a single peak in 1D with a general "spicy" descriptor. In 2D on a chiral column, four isomer peaks were resolved; only one isomer contributed the characteristic spicy/tobacco odor.

Benefits and Practical Applications of the Method

• Rapid switching between 1D and 2D modes without hardware reconfiguration.
• Parallel mass spectrometric and olfactory detection in both dimensions for comprehensive odor-active compound profiling.
• Solventless SPME provides concentrated sample introduction and tunable selectivity via fiber coatings.
• Enhanced peak capacity and resolution enables detection of trace components in complex matrices, aiding R&D, QA/QC, and shelf-life studies.

Future Trends and Potential Applications

Further integration with advanced data processing and automated odor description systems can streamline flavor analysis. Expanding the range of stationary phases, including novel chiral and ionic liquid columns, will broaden applications in food, fragrance, environmental, and clinical analyses. Coupling with high-resolution MS and real-time olfactometry may reveal new insights into odorant interactions.

Conclusion

The selectable 1D/2D GC-MS platform with SPME and olfactory detection offers a versatile, high-resolution approach for flavor compound analysis. Its ease of operation and ability to resolve trace-level compounds make it a valuable tool for food and fragrance laboratories.

References

1. Ochiai N, Sasimoto K. Two-dimensional GC with capillary flow technology. J Chromatogr A. 2010;1217:2903–2910.
2. Ochiai N, Sasimoto K. Low thermal mass column modules for 2D GC. J Chromatogr A. 2011;1218:3180–3185.
3. Buttery RG, Siefert RM, Guadagni DG, Ling LC. Pyrazines in fried potato aroma. J Agric Food Chem. 1971;19(5):969–971.