Acidity: what we're actually talking about
Free acidity is measured in a laboratory. It indicates the percentage of free fatty acids (as oleic acid) present in the oil.
Free fatty acids indicate that triglycerides (how fats are "packaged" in the olive) have broken down. This happens when:
- Olives have been damaged on the tree or during harvest
- They were poorly stored before milling (piled up, fermented)
- Too much time passed between harvest and pressing
- Olives suffered olive fly attacks or other pests
Acidity measures the quality of olives and process, not the flavour of the oil.
Why acidity isn't tasted
A surprising truth: the human body cannot sense an oil's acidity through its senses, whatever the value.
When you feel an oil "pinch" your throat or have a strong bitter aftertaste, you're sensing polyphenols, not acidity. These are different things:
- Acidity = chemical parameter. Tells about preservation. No perceptible taste.
- Pungency and bitterness = positive sensory attributes associated with several phenolic compounds. They can suggest their presence but do not, by themselves, measure freshness, quality or concentration.
Legal parameters
Under Delegated Regulation (EU) 2022/2104, an extra virgin oil must meet all the required parameters, including:
- Free acidity ≤ 0.8%
- Median of defects = 0 and median of fruitiness > 0
Acidity is therefore a necessary requirement, not an absolute ranking. Oils with the same value can differ in sensory profile and oxidation. Any batch-specific figure should be supported by a current laboratory report.
Polyphenols: the real "quality flavour"
Polyphenols give EVOO its intense flavour and health properties:
- Oleocanthal and related compounds: contribute to pungency perceived especially in the throat.
- Oleuropein derivatives: contribute to bitterness.
- Tyrosol, hydroxytyrosol and their derivatives: considered by the authorised EU health claim when its precise conditions are met.
The authorised claim requires at least 5 mg of hydroxytyrosol and its derivatives per 20 g of oil and the information that the beneficial effect is obtained with a daily intake of 20 g. Compliance must be demonstrated for the relevant batch by an appropriate analysis; it cannot be inferred from taste or cultivar.
