Analysis of Food Samples using Thin Film Solid Phase Microextraction (TF-SPME) and Thermal Desorption GC/MS

Significance of the Topic

Food products require precise monitoring of aroma and flavor profiles to ensure quality, authenticity, and safety. Semi-volatile and volatile compounds contribute to unique sensory characteristics, and rapid, solvent-free techniques are essential for broad analyte coverage and efficient detection of off-flavors.

Objectives and Study Overview

This study evaluates Thin Film Solid Phase Microextraction (TF-SPME) combined with thermal desorption GC/MS for profiling aroma and flavor compounds in high-fat food matrices. Target samples include dark chocolate, blue cheese, Caesar dressing, and strawberry cream cheese, focusing on method sensitivity, versatility, and ease of automation.

Methodology and Instrumentation

Sample preparation and extraction:

• 2.0 g aliquot of each food sample placed in a 20 mL screw-cap vial
• DVB/PDMS-coated carbon mesh TF-SPME device (20 × 4.8 mm) suspended in the headspace (alternatively immersed)
• Agitation at 40 °C for 3 h (250–500 rpm); extended extraction at 25 °C for strawberry cream cheese (15 h)
• Post-extraction drying, followed by thermal desorption in GERSTEL TDU and transfer to CIS inlet

Instrumentation:

• GERSTEL Multipurpose Sampler (MPS), Thermal Desorption Unit (TDU 2), Programmable Temperature Vaporizer (CIS 4)
• Agilent 7890A GC with 5977B MSD
• Chromatographic columns:
  • 30 m Rxi-5Sil MS (0.25 mm ID, 0.25 µm df) for dark chocolate
  • 30 m DB-Wax (0.25 mm ID, 0.25 µm df) for other samples
• Helium carrier, constant flow/pressure modes, optimized oven programs per sample

Main Results and Discussion

Dark chocolate:

• Detected pyrazines (e.g., tetramethylpyrazine), aldehydes, ketones, acids, alcohols, and terpenes contributing to cocoa and nutty notes
• High sensitivity for quality defects and off-aroma compounds

Blue cheese:

• Dominant methyl ketones (2-pentanone, 2-heptanone, 2-nonanone) from Penicillium fermentation
• Secondary alcohols and fatty acids defining characteristic mold-ripened flavor

Caesar dressing:

• Preservative sorbic acid and solvent ethyl acetate
• Black pepper terpenes (pinene, limonene, caryophyllene) and cheese-derived fatty acids

Strawberry cream cheese:

• Fruit esters (ethyl acetate, ethyl butyrate, ethyl 2-methylbutyrate) and acetoin at 25 °C extraction
• Enhanced Maillard reaction products (furfural, 5-hydroxymethylfurfural) at 40 °C, demonstrating sensitivity to processing-induced compounds

Benefits and Practical Applications

• Solvent-free, minimal sample preparation and high automation potential
• Broad analyte range covering volatile and semi-volatile compounds
• Rapid screening for quality control, troubleshooting, product development, and authenticity testing
• Quantitative capability with appropriate calibration standards

Future Trends and Applications

• Integration with multidimensional GC and high-resolution mass spectrometry for deeper compound characterization
• Development of tailored sorptive phases to target specific chemical classes
• Real-time monitoring and online TF-SPME coupling for process control
• Use of chemometric and AI-driven approaches for complex flavor profile analysis

Conclusion

TF-SPME combined with automated thermal desorption GC/MS on the GERSTEL MPS/TDU/CIS platform offers a robust, versatile solution for comprehensive aroma and flavor analysis in diverse food matrices, enabling efficient quality control and research applications.