Analysis of Aroma Compounds in Fatty Acid Containing Foods Using SPME Arrow-GC-MS

Significance of the Topic

Analysis of aroma compounds is essential for assessing food flavor quality and authenticity. Solid phase microextraction (SPME) combined with gas chromatography–mass spectrometry (GC-MS) is widely used, but fatty acid–rich matrices such as sake can cause severe peak tailing on polar columns, hindering comprehensive volatilome profiling.

Objectives and Overview of the Study

The study aimed to establish SPME Arrow–GC-MS conditions that minimize fatty acid extraction by adjusting sample pH, thereby enabling full aroma profiling of Japanese sake before and after two months of sherry cask aging. Comparative analysis of volatile profiles would reveal unique flavor components imparted by oak casks.

Methodology and Instrumentation

Samples of Daiginjo sake were diluted to 10 % ethanol and salted with NaCl. Tris(hydroxymethyl)aminomethane was added to adjust pH from ~4 to 8. Extraction used a PDMS SPME Arrow (100 µm, 20 mm length) by direct immersion at 30 °C for 60 min with stirring. Thermal desorption into splitless GC-MS followed a temperature program (40 °C→240 °C at 3 °C/min). Mass spectra were acquired in scan mode (m/z 35–350) and compounds annotated via NIST and FFNSC3 libraries.

Used Instrumentation

• GC-MS system: GCMS-TQ 8050 NX
• Autosampler: AOC-6000 Plus with SPME Arrow capability
• Column: Supelcowax 10 (30 m × 0.25 mm i.d., 0.25 µm film)
• SPME Arrow fiber: PDMS coating, 1.1 mm outer diameter, 100 µm film

Main Results and Discussion

At native pH 4, large fatty acid peaks (hexanoate, octanoate, decanoate, dodecanoate) exhibited severe tailing, obscuring co-eluting volatiles. Raising pH to 8 via Tris converted acids to their ionic forms, preventing retention on the nonpolar PDMS fiber and eliminating tailing. This enabled detection of otherwise hidden compounds. Sherry cask aging led to significant increases in:

• Aliphatic alcohols (1-hexanol, 1-decanol) and aging-related ketones (2-nonanone)
• Organic acid esters (diethyl succinate, 2-phenylethyl acetate, whiskey lactone)
• Fatty acid esters (ethyl nonanoate, diethyl azelate)
• Terpenes and terpene alcohols (cadinene, eudesmol isomers, phyllocladanol)

Some fruity esters (ethyl butyrate, ethyl hexanoate) decreased after storage due to conversion or co-elution with introduced compounds.

Benefits and Practical Applications

• Comprehensive aroma profiling in acid-rich foods and beverages without peak tailing
• Non-targeted metabolic screening of volatile constituents in sake, vinegar, wine, and similar matrices
• Improved reproducibility and sensitivity afforded by SPME Arrow’s high adsorbent volume

Future Trends and Possibilities

Integration of this pH-adjusted SPME Arrow method with advanced deconvolution software and multivariate data analysis will enable deeper metabolomic insights. Expanded fiber chemistries and dynamic headspace approaches could broaden applicability to complex matrices. Coupling with AI-driven interpretation promises rapid authenticity testing and flavor optimization in food and beverage research.

Conclusion

Adjusting sample pH with Tris prevents fatty acid extraction in SPME Arrow–GC-MS, overcoming peak tailing and unlocking comprehensive volatilome analysis of sake and other acidic matrices. This approach revealed distinct aroma compounds introduced by sherry cask aging, demonstrating its value for quality control and flavor research.

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