Flavor Profiling of Different Olive Oils with Rancidity-Monitoring by Thermal Extraction GC/MS

Significance of the Topic

Virgin olive oil is valued for its delicate taste and aroma, making flavor profiling vital for quality assessment and consumer acceptance. Off-flavors, resulting from lipid oxidation, can degrade product value and indicate rancidity. Rapid, sensitive analytical methods that capture both volatile and semi-volatile contributors to flavor are essential in research, quality control, and supply chain monitoring.

Objectives and Study Overview

This study demonstrates a solvent-free thermal extraction GC–MS approach to profile flavor and off-flavor compounds in virgin olive oils and to monitor rancidity under accelerated oxidation conditions. Three commercially obtained Italian olive oils from Tuscany, Bardolino, and Liguria were compared to assess regional compositional differences. Additionally, a sunlight-exposure experiment evaluated changes in volatile profiles associated with rancidity.

Methodology and Instrumentation

A direct thermal extraction technique was employed, requiring only 10 µL of oil. Samples were injected into inert desorption tubes, thermally ramped to release analytes, and cryo-trapped in a programmable temperature vaporization inlet at –150 °C. Subsequent inlet heating to 280 °C transferred analytes into the GC–MS system.

Used Instrumentation

• Agilent 6890 GC coupled with 5973 mass-selective detector
• Gerstel Thermal Desorption System (TDS 2 & TDS A) with autosampler
• Gerstel Cold Injection System (CIS 4) for PTV trapping
• 50 m × 0.2 mm, 0.5 µm HP-1 capillary column

Main Results and Discussion

Analysis identified over 60 volatile and semi-volatile compounds, including alcohols, aldehydes, ketones, acids, and hydrocarbons. Characteristic aroma contributors such as hexanal (green note), pentanal (pungent), and 2,4-decadienal (deep-fried) were detected. Comparative profiling revealed regional differences in compound occurrence and abundance. In the rancidity experiment, sunlight-exposed oil exhibited marked increases in oxidation markers: hexanal rose more than fivefold, trans-2-heptenal and nonanal increased dramatically, and additional products such as 2-butenal and 6-methyl-5-heptene-2-one appeared. This highlights the method’s sensitivity to oxidative changes and suitability for rancidity monitoring.

Benefits and Practical Applications

• Solvent- and distillation-free workflow reduces preparation time and environmental impact
• Minimal sample volume (10 µL) enables high-throughput screening
• Automation potential supports routine quality control in laboratories and production sites
• Comprehensive detection spans volatiles and semi-volatiles, linking aroma and taste profiles

Future Trends and Opportunities for Utilization

Advancements may include coupling with high-resolution MS for detailed compound identification, integration with multi-dimensional GC for enhanced separation, and application to a wider range of edible oils and fats. Real-time monitoring of storage and processing effects could further improve product traceability and shelf-life prediction.

Conclusion

Direct thermal extraction GC-MS offers a streamlined, sensitive, and comprehensive approach to olive oil flavor profiling and rancidity assessment. Its ease of automation and broad analyte coverage make it an attractive tool for research, quality control, and industrial analytics.

Reference

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