1. What it measures
Olive oil is mostly triglycerides: three fatty acids bound to a glycerol backbone. When fruit is bruised, left in heaps, attacked by fly or fungus, or simply picked and milled too slowly, enzymes and microbes start cutting fatty acids loose. Free acidity is the weight of those loose fatty acids as a share of the oil, expressed as oleic acid. An oil at 0.2% has two grams of free fatty acids in a kilogram.
It is, in other words, a record of the fruit’s condition and the speed of the mill. Sound olives picked from the tree and milled within a day give 0.1–0.3%. Fruit off the ground, fermenting in sacks for a week, gives 1% and more, and the oil goes to the refinery.
2. The limits
| Category | Free acidity | Also required |
|---|---|---|
| Extra virgin olive oil | ≤ 0.8 g/100 g | Peroxide ≤ 20 meq O₂/kg · K232 ≤ 2.50 · K270 ≤ 0.22 · no sensory defect, fruity > 0 |
| Virgin olive oil | ≤ 2.0 g/100 g | Peroxide ≤ 20 · slight defects allowed (median ≤ 3.5) |
| Lampante (not for retail) | > 2.0 g/100 g | Sent for refining |
| Olive oil (refined + virgin) | ≤ 1.0 g/100 g | A blend of refined oil with some virgin |
The EU categories in Regulation 2022/2104 and the chemical limits behind them. Acidity is one test of several; a taste panel is another.
Note what the table implies: an oil can be at 0.3% and still fail to be extra virgin if the panel finds a defect, and an oil at 0.75% can pass. Acidity is necessary, not sufficient.
3. Not a taste
Free fatty acids at these levels have no taste and no smell. The “acidity” people think they detect in a sharp, peppery oil is pungency from polyphenols, which is a different thing entirely and a positive attribute. A bland refined oil can have lower acidity than a magnificent early-harvest Coratina. This is also why EU rules forbid printing acidity on a label unless peroxide, waxes and UV absorbency are printed alongside it in the same size: on its own it invites exactly this misreading.
0.2% against 0.5% is a story about the harvest. It is not a flavour.
4. What a low figure tells you
A very low figure — 0.1 to 0.2% — tells you the producer picked sound fruit and milled it fast. That is worth knowing, because the same care usually shows up as freshness and clean aromas. It does not tell you the oil is intense, or high in phenols, or from a good variety, and it says nothing about how long the bottle sat in a tank before bottling. Read it as one line of a technical sheet, next to the harvest date, the polyphenol figure and the method, and weight it accordingly.