The lab and tasting terms used across our rankings, in plain English.
- Polyphenols (biophenols)
- A family of antioxidant compounds in olives. In olive oil the most important are oleocanthal, oleacein, oleuropein- and ligstroside-derivatives, hydroxytyrosol, and tyrosol. Measured in mg/kg (parts per million).
- Oleocanthal
- The phenol responsible for the peppery throat sting of fresh extra virgin olive oil. Studied for anti-inflammatory properties; one of the two compounds qNMR quantifies most precisely.
- Oleacein
- The bitter-tasting counterpart to oleocanthal, derived from oleuropein. Typically the most abundant single phenol in high-phenolic oils.
- Hydroxytyrosol
- A small, potent phenol. The EU health claim is conditioned on hydroxytyrosol and its derivatives: at least 5 mg per 20 g of oil, consumed daily.
- qNMR
- Quantitative Nuclear Magnetic Resonance. Quantifies individual phenols (oleocanthal, oleacein, etc.) without separation. The reference method used by the University of Athens group for high-phenolic oils.
- HPLC (HPLC-DAD)
- High-Performance Liquid Chromatography. Separates individual phenolic compounds and sums them. The IOC's official method for phenol quantification uses this approach.
- Folin-Ciocalteu
- A colorimetric assay measuring total reducing capacity, expressed as 'total phenols'. Reads systematically higher than qNMR or HPLC for the same oil — which is why values must never be compared across methods.
- Acidity (free fatty acidity)
- The percentage of free oleic acid. A marker of fruit quality and processing speed, not taste. Extra virgin requires ≤0.8%; excellent oils are often ≤0.3%.
- Peroxide value
- Measures primary oxidation in meq O2/kg. Lower is fresher; extra virgin requires ≤20, and well-made fresh oils are usually under 10.
- K232 / K270 / ΔK
- UV absorbance values that detect oxidation and refining. Part of a full quality panel; values outside extra-virgin limits indicate degradation or adulteration.
- Harvest date vs best-before date
- Polyphenols decline from the moment of milling. The harvest date tells you the oil's true age; the best-before date is a shelf-life convention, usually set 18–24 months after bottling.
- Early harvest
- Oil pressed from less-ripe (green) olives. Yields less oil per tree but substantially higher polyphenol levels — most ultra-high-phenolic oils are early harvest.
- Certificate of analysis (COA)
- The lab report stating measured values for a specific batch. The strongest form of evidence for a polyphenol claim, especially from a named, independent laboratory.
- mg/kg (ppm)
- Milligrams of phenols per kilogram of oil — the standard unit for polyphenol content. Equivalent to parts per million.