Quality Analysis of Extra Virgin Olive Oils – Part 6 Nutritive Benefits – Phenolic Compounds in Virgin Olive Oil

Significance of the Topic

Virgin olive oil is rich in hydrophilic phenolic compounds that contribute to its antioxidant capacity, sensory attributes, and potential health benefits. These bioactive substances protect the oil from oxidation and support various biological effects in humans.

Objectives and Study Overview

The study aims to compare high performance liquid chromatography (HPLC) and ultra high performance liquid chromatography (UHPLC) methods for quantifying hydrophilic phenols in olive oil. Method transfer, analytical performance, and total phenol content determination were evaluated across multiple oil samples.

Methodology and Instrumentation

• Instrumentation
• Agilent 1260 Infinity Quaternary LC system with quaternary pump, autosampler, thermostatted column compartment, diode array detector
• Agilent ZORBAX Eclipse Plus C18 columns for HPLC (4.6 × 250 mm, 5 µm) and UHPLC (3 × 100 mm, 1.8 µm)
• Sample Preparation
• Liquid–liquid extraction following International Olive Council protocol (COI/T.20/Doc No. 29)
• Use of syringic acid as internal standard and methanol/water extraction solvent
• Chromatographic Conditions
• HPLC ternary gradient (water with 0.2 % H3PO4, methanol, acetonitrile), run time 72 minutes
• UHPLC ternary gradient adapted for sub-2 µm column, run time 20.5 minutes

Main Results and Discussion

Both methods showed excellent precision for retention time (RSD < 0.055 % HPLC, < 0.08 % UHPLC) and peak area (RSD < 0.35 % HPLC, < 1.35 % UHPLC). Linearity for tyrosol and syringic acid standards was confirmed (r > 0.99997). Total phenol contents measured in 11 olive oils ranged from approximately 198 to 708 mg/kg (HPLC) and 211 to 788 mg/kg (UHPLC), with strong agreement between methods. UHPLC reduced analysis time threefold and solvent consumption by over 80 %.

Benefits and Practical Applications

• Substantial reduction in analysis time and solvent usage
• High analytical precision and linearity suitable for routine quality control
• Reliable quantification of total phenols for authenticity and nutritional assessments

Future Trends and Potential Applications

The integration of two-dimensional liquid chromatography and mass spectrometry could enhance resolution of coeluting compounds. Further miniaturization and automation will support high-throughput screening in food quality laboratories. Expanding the range of detectable phenolics and improving inline sample preparation are anticipated developments.

Conclusion

Transferring the IOC HPLC method to UHPLC with sub-2 µm columns maintains data quality while significantly improving throughput and sustainability. This approach is well suited for routine phenolic profiling and quality evaluation of virgin olive oils.

Reference

1. Aparicio P., Ruiz A. Authentication of vegetable oils by chromatographic techniques. Journal of Chromatography A. 2000;881:93–104.
2. Schneider S. Quality Analysis of Virgin Olive Oils – Part 1. Agilent Application Note. 2013;5991-1894EN.
3. Schneider S. Quality Analysis of Virgin Olive Oils – Part 2. Agilent Application Note. 2013;5991-1985EN.
4. Schneider S. Quality Analysis of Virgin Olive Oils – Part 3. Agilent Application Note. 2013;5991-1896EN.
5. Beltrán G. et al. Evaluation of virgin olive oil bitterness by total phenol content analysis. European Journal of Lipid Science and Technology. 2007;108:193–197.
6. El Riachy M. et al. Hydrophilic antioxidants in virgin olive oil. Part 1: Phenolic acids. European Journal of Lipid Science and Technology. 2011;113:678–691.
7. Schneider S. Quality Analysis of Virgin Olive Oils – Part 4. Agilent Application Note. 2013;5991-2180EN.
8. Schneider S. Quality Analysis of Virgin Olive Oils – Part 5. Agilent Application Note. 2013;5991-2774EN.
9. International Olive Council. Determination of Biophenols in Olive Oils by HPLC. COI/T.20/Doc.29. 2009.
10. Owen R.W. et al. Olive-oil consumption and health: the possible role of antioxidants. The Lancet Oncology. 2000;1:107–112.
11. García A. et al. Effect of refining on the phenolic composition of crude olive oils. JAOCS. 2006;83(2):159–164.
12. Naegele E. Qualitative and quantitative determination of phenolic antioxidant compounds in red wine and fruit juice with the Agilent 1290 Infinity 2D-LC Solution. Agilent Application Note. 2012;5991-0426EN.
13. Reichenbach M., Naegele E. Two-dimensional separation of polyphenols in beverages using the Agilent 1290 Infinity 2D-LC Solution. Agilent Application Note. 2013;5991-1455EN.