Some bottles carry a small number: “acidity 0.3 %”. It looks like a promise of quality, and that is how it is meant. But it says something different from what most readers assume, and about taste it says almost nothing. The best proof of that sits in the law itself: refined olive oil, which is neutral in flavour, has to have a lower acidity than extra virgin olive oil.
What acidity actually measures
What is measured is the share of free fatty acids in the oil. In the trade standard of the International Olive Council the figure is listed as “Free acidity % m/m expressed in oleic acid”: a proportion by mass, expressed as oleic acid. The definition of the top grade reads “free acidity, expressed as oleic acid, of not more than 0.80 grams per 100 grams”.
Two things follow. First, this is a weight figure, not a pH value and not a tasting note: 0.8 grams per 100 grams. Second, it is a laboratory result – the standard lists the determination of free acidity as an analytical method of its own. Nobody tastes this value out of the bottle, and no kitchen method produces it.
The limits, category by category
The figures come from the trade standard of the International Olive Council and, for the two virgin grades, match Annex I to Delegated Regulation (EU) 2022/2104. Switzerland adopts the requirements for olive oil by reference: Annex 2 of the ordinance of the Federal Department of Home Affairs on foodstuffs of plant origin, mushrooms and table salt declares the European annex applicable.
| Category | Free acidity (as oleic acid) |
|---|---|
| Extra virgin olive oil | max. 0.80 % |
| Virgin olive oil | max. 2.0 % |
| Lampante oil (may not be sold to consumers) | over 2.0 % |
| Refined olive oil | max. 0.30 % |
| Olive oil composed of refined and virgin olive oils | max. 1.0 % |
| Olive pomace oil | max. 1.0 % |
A note on precision: the Olive Council standard also knows a grade called “ordinary virgin olive oil” at no more than 3.3 per cent, and places lampante only above 3.3 per cent. European and Swiss law have no such intermediate grade; there, lampante begins above 2.0 per cent. The two systems are therefore identical at 0.80 and 2.0 – not all the way down.
Which categories may appear on a Swiss shelf at all is governed by the same ordinance: only extra virgin olive oil, virgin olive oil, “olive oil composed of refined and virgin olive oils” and olive pomace oil may be supplied to consumers. Lampante is absent from that list – it has to be refined first. The full overview of the grades and their other limits is in What Is Extra Virgin Olive Oil?.
Why a low number is not a seal of quality
Now to the row set in bold in the table. Refined olive oil may hold no more than 0.30 per cent free acidity – less than half of what an extra virgin oil is allowed. But refined oil is precisely the oil from which refining has removed the flavour, the polyphenols and the vitamin E. A low acidity figure there is not the result of better fruit but of a chemical cleaning. Which health claims actually depend on those polyphenols is sorted out in Olive Oil and Health: What the Evidence Shows.
So the equation “less acidity means better oil” collapses on the legislator's own numbers. Acidity is a condition, not a ranking.
The second reason is the sensory assessment. For the extra virgin grade the law demands not only chemistry but a judgement: the median of the defects must be 0.0 and the median of the fruity attribute above 0.0. The testing method of the International Olive Council states this expressly for the top grade. What matters is how the median of defects is defined – as the median of the defect perceived with the greatest intensity. A single clearly perceptible defect is therefore enough to lose the grade.
How much that matters in practice is shown by a Swiss campaign. In an interregional survey, 15 cantons took part with 96 samples of “extra vergine” in total. Eleven per cent failed on sensory deviations that did not justify the designation – and only 5 per cent on chemical differences. More oils were caught by the panel than by the laboratory values. A bottle can sit comfortably inside 0.8 per cent and still not be extra virgin olive oil.
What “0.3 %” on a bottle means
In law: nothing special. There is no grade at 0.3 per cent and no bonus for it. The figure sits well below the only threshold that the designation turns on, namely 0.80 per cent. As advertising it works, because it radiates precision; as a buying criterion it is weak, for the reason in the section above: 0.3 per cent is exactly the ceiling that applies to refined olive oil.
What the number does show is that the producer measured and is willing to print the result. That is a signal about the care taken in the mill – not about the taste in the glass.
Why the number almost never appears on the label
This is the most interesting part, and it explains why you hardly ever find the figure in a supermarket. Swiss law does not let it stand alone. Article 12 paragraph 6 of the ordinance on foodstuffs of plant origin, mushrooms and table salt provides that stating the acidity, or the maximum acidity, of olive oil, virgin olive oil, extra virgin olive oil and olive pomace oil is permitted only if the values for the peroxide number, the wax content and the absorption in the ultraviolet range, determined in accordance with Regulation (EEC) No 2568/91, are given in addition, in the same font size and in the same field of vision.
Anyone who prints an acidity figure on a label therefore has to print three more laboratory values beside it – equally large and in the same field of vision. European law knows the same rule: Article 10 of Delegated Regulation (EU) 2022/2104 permits an indication of the maximum acidity expected by the date of minimum durability only if it is accompanied by the maximum values for peroxide, the wax content and the ultraviolet absorption, in marking of the same size and in the same visual field.
The legislator, in other words, does not trust the single number either. It treats acidity as one of four figures that only make sense together – and in doing so makes it unattractive for marketing. Which is exactly why most bottles say nothing at all.
What on the label says more than the acidity
- The mandatory wording for the grade. Extra virgin olive oil must carry, in addition to the name of the product, the statement that it is of the highest category, obtained directly from olives and solely by mechanical means. If that is missing, something is wrong.
- The harvest year. Extra virgin and virgin olive oil may be labelled with a harvest year – but only if 100 per cent of the contents come from that year. That is harder information than any acidity figure.
- “First cold pressing” and “cold extraction” are defined terms. The first is permitted only where the oil was obtained by the first mechanical pressing of the olive paste at no more than 27 °C in a traditional system with a hydraulic press; the second only for percolation or centrifugation at no more than 27 °C. Both describe a process, not an acidity.
- Claims about taste are tied to an assessment. References to organoleptic characteristics of taste or smell may be made only for virgin oils, and the regulated terms only on the basis of a sensory examination. If you want to talk about flavour, you have to have it tasted – calculating will not do.
And then there is what no label reveals: how the bottle was stored. How not to spoil the oil after buying it is covered in How to Store Olive Oil So It Stays Fresh Longer. What part free fatty acids play in a hot pan is discussed in Cooking with Olive Oil: What the Smoke Point Really Means.
Frequently asked questions
Is an oil at 0.2 per cent better than one at 0.6 per cent?
Not automatically. Both satisfy the condition for extra virgin olive oil, and taste is settled by the tasting panel, not by the figure. As a reminder: refined olive oil has to come in below 0.30 per cent and tastes of nothing.
Does acidity have anything to do with a sour taste?
The figure is a proportion by mass of free fatty acids, determined in a laboratory – not a tasting note. Under Swiss law, references to taste and smell may in any case be made only for virgin oils, and only on the basis of a sensory examination.
Why does acidity so rarely appear on the bottle?
Because it may not stand alone. Anyone stating it must also print the peroxide value, the wax content and the UV absorption in the same font size and the same field of vision. Few brands want four laboratory values on the front.
What is lampante oil?
Virgin olive oil with more than 2.0 per cent free acidity. It is not on the list of oils that may be supplied to consumers and has to be refined first.
Does “first cold pressing” mean lower acidity?
No. The term is defined by the process – a first mechanical pressing at no more than 27 °C – and says nothing about the acidity value.
Sources
- International Olive Council: Trade Standard Applying to Olive Oils and Olive Pomace Oils, COI/T.15/NC No 3/Rev. 22
- International Olive Council: Standards and methods (current revisions)
- International Olive Council: Sensory analysis of olive oil – method for the organoleptic assessment of virgin olive oil, COI/T.20/Doc. No 15/Rev. 11
- Delegated Regulation (EU) 2022/2104 on marketing standards for olive oil
- Swiss ordinance on foodstuffs of plant origin, mushrooms and table salt (VLpH, SR 817.022.17), Articles 9–12 and Annex 2
- Food Safety Authority of Ireland: Olive oil – labelling requirements under Delegated Regulation (EU) 2022/2104
- Canton of Zurich: one in ten «extra vergine» olive oils shows sensory defects
