1Beyond the Commercial Label
When we come across the chemical analysis report for an olive oil, we find several terms that can seem cryptic. Besides acidity, peroxides and polyphenols stand out.
Peroxides: Oxidation in Progress
The peroxide value (expressed in mEq O₂/kg) indicates oxidative alteration. The law sets the limit at 20 mEq O₂/kg for extra virgin olive oil. An excellent oil is often between 4 and 8.
Polyphenols: The Natural Defense
They are the real treasure of EVOO: they counter oxidation and keep the peroxide level low over time. A high polyphenol value (> 300–400 mg/kg) indicates an oil with a strong sensory character — bitter and spicy — and an extremely long shelf life.
- < 100 mg/kg: poor oil (industrial, aged)
- 100–300 mg/kg: commercial standard
- 300–500 mg/kg: good quality
- > 500 mg/kg: absolute excellence
Always ask your producer for the lab results — a good olive mill will be happy to provide them.