Quality Analysis of Extra Virgin Olive Oils – Part 8

Significance of the topic

Extra virgin olive oil is valued for its nutritional and health benefits, driven largely by its unique triacylglycerol (TAG) composition. Accurate profiling of TAGs enables authentication of olive oil varieties, detection of adulteration and verification of geographic origin. This approach supports quality control in the food industry and safeguards consumer trust.

Objectives and study overview

The study aimed to develop a reliable method for profiling 17 TAG species in extra virgin olive oil using solid phase extraction (SPE) and isocratic reversed-phase high performance liquid chromatography (RP-HPLC) with refractive index detection (RI). The resulting TAG fingerprint was applied to classify monovarietal oils and distinguish them from blends and refined samples.

Methodology and instrumentation

Agricultural oil samples, including nine extra virgin and one refined olive oil, underwent SPE cleanup based on Commission Regulation (EEC) No 2472/97, adapted to Agilent BondElut cartridges. One gram of oil was dissolved in petroleum ether–diethyl ether (87:13) and loaded onto the cartridge, followed by elution and solvent evaporation. A 5% solution in acetone was injected into an Agilent 1260 Infinity II LC system equipped with a Superspher RP-18 column and refractive index detector. Chromatographic conditions comprised an acetone–acetonitrile (60:40) isocratic run at 1 mL/min, 55 min total time, and 30 °C column temperature.

Key results and discussion

Seventeen TAGs were baseline-separated and quantified with high precision. Retention time relative standard deviations (RSD) were below 0.1% for most compounds, and peak area RSDs were under 1%. A principal component analysis (PCA) using normalized TAG percentages demonstrated clear clustering of monovarietal oils by variety. Notably, triolein (OOO) accounted for 38–46% of total TAGs, and specific minor species such as trilinolein (LLL) served as markers for seed oil adulteration.

Benefits and practical applications

• Authentication of olive oil variety and geographic origin.
• Rapid detection of adulteration with seed oils.
• Quality assurance in industrial and regulatory laboratories.
• Creation of TAG fingerprint databases for traceability.

Future trends and applications

Advances may include coupling HPLC with mass spectrometry for enhanced sensitivity and structural elucidation of TAGs, implementing high-throughput automated SPE workflows, and expanding chemometric models with larger databases. Miniaturized and portable LC-RI systems could enable on-site quality control in olive oil mills and distribution centers.

Conclusion

The presented SPE-HPLC-RI method delivers precise quantification of olive oil TAGs and supports reliable classification of monovarietal and blended oils. Its robustness and simplicity make it suitable for routine quality control, authenticity testing, and regulatory compliance.

References

1. Aparicio R., Ruiz A. Authentication of vegetable oils by chromatographic techniques. J. Chromatogr. A 2000, 881, 93–104.
2. Schneider S. Quality Analysis of Virgin Olive Oils – Part 1. Agilent Technologies Application Note 5991-1894EN, 2013.
3. Schneider S. Quality Analysis of Virgin Olive Oils – Part 2. Agilent Technologies Application Note 5991-1985EN, 2013.
4. Schneider S. Quality Analysis of Virgin Olive Oils – Part 3. Agilent Technologies Application Note 5991-1896EN, 2013.
5. Schneider S. Quality Analysis of Virgin Olive Oils – Part 4. Agilent Technologies Application Note 5991-2180EN, 2013.
6. Schneider S. Quality Analysis of Extra Virgin Olive Oils – Part 5. Agilent Technologies Application Note 5991-2774EN, 2013.
7. Schneider S. Quality Analysis of Virgin Olive Oils – Part 6. Agilent Technologies Application Note 5991-3801EN, 2014.
8. Schneider S. Analysis of Virgin Olive Oils – Part 7. Agilent Technologies Application Note 5991-4515EN, 2014.
9. Boskou D., et al. Olive Oil Composition. American Oil Chemists’ Society, 2006.
10. Commission Regulation (EC) No 2472/97 on the characteristics of olive oils and olive-pomace oils and on the relevant methods of analysis. Official Journal of the European Communities, 1997.