Identifying key odor compounds in bourbon using solvent-free aroma dilution analysis and a novel software for interpreting GC-O data

Importance of the Topic

Bourbon aroma compounds determine sensory character and commercial success. Gas chromatography–mass spectrometry coupled with olfactometry (GC-MS/O) provides simultaneous instrumental and sensory evaluation of complex matrices. Applying solvent-free aroma dilution analysis (ADA) with stir bar sorptive extraction (SBSE) enhances detection sensitivity while maintaining native sample conditions.

Objectives and Study Overview

This study aimed to implement ADA on direct immersion SBSE extracts of bourbon, determine flavor dilution (FD) factors for aroma-active compounds, and utilize novel software to streamline interpretation of GC-O data. The focus was to identify key odorants with highest sensory impact.

Methodology and Instrumentation

Bourbon was diluted and subjected to PDMS-coated SBSE. Thermal desorption occurred in GERSTEL TDU 2 and CIS 4, with split ratios varied to generate overall dilutions up to 201. An Agilent 7890 GC and 5977 MSD provided chromatographic separation and mass spectral identification. Effluent was split 2:1 to a GERSTEL ODP 4 for olfactory detection. The GERSTEL Olfactory Data Interpreter (ODI) software overlaid chromatograms and olfactograms, enabled cumulative olfactogram views, and supported AEDA-like FD calculations.

Main Results and Discussion

Thirty-three aroma-active compounds were detected. Five compounds—ethyl isovalerate, ethyl hexanoate, phenylethyl alcohol, ethyl octanoate, and cis-oak lactone—exhibited the highest FD factor of 201. Regression of ln(peak area) vs ln(FD) showed slopes near –1 and r² > 0.98, confirming linearity. ODI visualization simplified odor intensity mapping and peak assignment.

Benefits and Practical Applications

Solvent-free ADA SBSE reduces sample preparation time and maintains matrix interactions. Determining FD factors assists in flavor optimization, quality control, and benchmarking of spirits. The ODI software accelerates data processing, improves reproducibility, and facilitates comprehensive aroma profiling.

Future Trends and Applications

Opportunities include integrating automated sensory panels, expanding ADA SBSE to other beverages and food matrices, and combining results with chemometric models for predictive flavor assessment. Real-time aroma monitoring during production could further enhance quality management.

Conclusion

The combination of solvent-free ADA SBSE and advanced software delivers a robust workflow for identifying and quantifying key odorants in bourbon, effectively bridging analytical and sensory dimensions to support product development.

References

1. Feng X et al. Food Chemistry. 187 (2015): 44–52
2. Fraatz MA et al. European Food Research and Technology. 244 (2018): 949–957