Not all polyphenols are the same.
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Anyone comparing polyphenol-rich olive oils will quickly realize: the numbers don't add up. One oil advertises 400 mg/kg. The next one 1,800. A third, 2,500. Are some oils truly five times as potent as others?
Sometimes. But usually, they are simply measured differently.
Two methods, two different answers
There are two common procedures for measuring the polyphenol content in olive oil – and they do not speak the same language.
HPLC (High-Performance Liquid Chromatography) is the method recognized by the International Olive Council and used in the European Union. It breaks the oil down into its individual phenolic compounds and specifically records those linked to measurable health effects – primarily hydroxytyrosol, tyrosol, and their derivatives (the oleuropein and ligstroside aglycones). The process is selective, reproducible, and clearly defined.
NMR (Nuclear Magnetic Resonance Spectroscopy) – the basis of the qNMR method developed in Greece and widely used there – measures more broadly. It captures a significantly larger spectrum of phenolic compounds, including many that HPLC does not count at all. The result: a higher number.
Both methods are scientifically valid. They simply measure different things.
Why Greek olive oils often show the highest values
When Greek oils are advertised with 1,500 or 2,000 mg/kg, two factors usually come together.
First, Greek olive oils – especially from the early harvest of the Koroneiki olive – are naturally particularly rich in phenols. Variety, terroir, and harvest time result in oils with an exceptionally high polyphenol content.
Second, they are frequently tested using the NMR method, which by design yields higher values. The same oil looks differently potent by HPLC and by NMR – not because the oil has changed, but because the yardstick has changed.
Why we use the European standard
At Solio, we state our polyphenol content based on HPLC because it is the method accepted by the European Union for official health claims regarding olive oil. To justify this claim, an oil must contain at least 5 mg of hydroxytyrosol and its derivatives per 20 g – measured by HPLC. This corresponds to around 250 mg/kg.
According to this standard, our oil reaches 954 mg/kg. Almost four times the threshold – and significantly higher than what most commercial olive oils offer.
What our oil shows according to the Greek method
For comparison: The same Solio oil is 50 to 60 percent higher according to the NMR-based Greek method – at approximately 1,450 to 1,525 mg/kg. This firmly places it in the range of high-quality, polyphenol-rich Greek oils.
We could advertise with this number. It would be impressive on the label. But it would not be directly comparable to the HPLC values that European consumers see most often – and it is not the measure upon which the regulated health claim is based.
We prefer a number that means something concrete over a larger one that remains vague.
The conclusion
Anyone comparing polyphenol values of different olive oils should always check which measurement procedure was used. If it is not mentioned, the numbers are likely not directly comparable. And anyone looking for an oil that meets the EU health claim for olive oil should ensure the value is based on an HPLC test according to the IOC method.
Bigger is not always better. Concrete is.
FAQ
What is the difference between HPLC and NMR in polyphenol measurement?
HPLC (High-Performance Liquid Chromatography) is the method recognized by the International Olive Council and the EU. It specifically measures individual phenolic compounds such as hydroxytyrosol and tyrosol. NMR (Nuclear Magnetic Resonance Spectroscopy) captures a broader spectrum of phenolic compounds and, by design, provides higher values – typically 50–60% more for the same oil.
Which method forms the basis of the EU health claim?
The EU health claim for olive oil is based on HPLC measurement according to the IOC method. An oil must contain at least 5 mg of hydroxytyrosol and its derivatives per 20 g – which corresponds to about 250 mg/kg.
Why does Solio not state the higher NMR value?
Because the HPLC value is directly comparable to the EU standard and the regulated health claim. A larger number without a clear reference point would be less meaningful for consumers. Solio’s oil reaches 954 mg/kg by HPLC and approx. 1,450–1,525 mg/kg by NMR.
Are Greek olive oils really more potent?
They are often indeed richer in phenols – especially early-harvest Koroneiki oils. At the same time, they are more frequently tested by NMR, which makes the values appear additionally higher. Both factors play a role.