Olive Oil Acidity: What It Really Means
Olive oil acidity is a lab measure of free fatty acids, not sourness. Learn how it is measured, what the 0.8% extra virgin limit means, and why low acidity alone is not enough.
Quick answer: Olive oil acidity (free acidity) is the percentage of free fatty acids in the oil, measured in a lab and expressed as oleic acid. It is not a taste and not a pH value. EU rules and the International Olive Council standard allow extra virgin olive oil a maximum of 0.8%. Careful producers are usually far below that, and our published lab analyses show 0.18–0.35%.
Olive oil acidity is the most quoted number on a bottle and the most misunderstood. It has nothing to do with how sharp or sour the oil tastes, and you cannot detect it on the palate at all. It is a laboratory measurement, and once you know what it records, it becomes a genuinely useful clue about how the olives were treated.
Olive oil acidity at a glance
- Free acidity is the share of fatty acids that have broken away from their original structure, expressed as a percentage of oleic acid.
- It is measured in a lab, not by tasting. Free fatty acids have no flavor of their own.
- To be sold as extra virgin, an oil must test at or below 0.8% free acidity. That is a legal ceiling, not a target.
- A low number points to healthy fruit pressed quickly. It does not prove freshness, flavor or polyphenol content.
What olive oil acidity actually measures
Olive oil is mostly made of triglycerides: three fatty acids attached to a glycerol backbone. When that structure is damaged, some fatty acids come loose. These are free fatty acids, and free acidity is the percentage of them in the oil, calculated as if all of them were oleic acid, the main fatty acid in olive oil.
So when a label says 0.3% acidity, it does not mean the oil is acidic in the way a lemon or vinegar is. It means that about 0.3 g of every 100 g of oil is free fatty acid. The word is borrowed from chemistry, and it misleads almost everyone who meets it for the first time.
How free acidity is measured
The oil is dissolved in a solvent and titrated with a measured alkaline solution until the free fatty acids are neutralized. The amount of alkali used gives the percentage. It is a standard laboratory method, which is why the figure is comparable from one oil to the next, and why it cannot be judged by taste or smell.
If you have ever heard someone claim they can taste the acidity of an oil, they are most likely tasting a different defect, such as rancidity or fustiness. Acidity itself is invisible on the tongue.
Why low acidity reflects how the fruit was handled
Free fatty acids form when the fruit is bruised, fermented, attacked by olive fly or left waiting too long between the tree and the mill. Enzymes in the damaged fruit start breaking down the oil before it is even extracted. That is why acidity works as a summary of everything that happened before the mill.
Hand-picking into sacks instead of shaking the olives onto the ground, and pressing within hours instead of days, are what keep the number low. A low figure is evidence of a careful process rather than of a particular variety. It is also one reason fast, cold extraction matters as much as the grove itself. Our production standards describe how we pick by hand and mill the fruit the same day.
Olive oil acidity limits: extra virgin, virgin and lampante
The grades of olive oil are defined in EU rules (Commission Delegated Regulation (EU) 2022/2104, which replaced the older Regulation (EEC) No 2568/91), which follow the International Olive Council standards. Free acidity is only one of the criteria.
- Extra virgin: free acidity of 0.8% or less, plus sensory and chemical criteria described below.
- Virgin: free acidity of up to 2.0%.
- Lampante: free acidity above 2.0%. It is not fit for direct consumption and is normally refined.
Notice that refining removes free fatty acids. A refined oil can therefore show a very low acidity and still be a plain, flavorless oil. This is the clearest example of why the number should never be read on its own.
Olive oil acidity is not enough on its own
A low-acidity oil can still be old, oxidized or dull. For extra virgin, the same regulation sets further limits, and these are the numbers worth reading next to acidity:
- Peroxide value: 20 mEq O2/kg at most. It shows early oxidation.
- K232 and K270: no more than 2.50 and 0.22. They indicate oxidation and aging, and K270 is also affected by refining.
- Sensory assessment: a trained panel must find no defects and some fruitiness. No instrument replaces this step.
Beyond the legal tests, two things matter to us as buyers and as producers. Polyphenols are the compounds behind the pepper and bitterness of a fresh oil, and acidity tells you nothing about how many there are. Our guide to the power of polyphenols explains why. And the harvest date tells you how long ago the oil was made. For a practical checklist, see how to spot a truly great extra virgin olive oil.
Acidity tells you how the fruit was treated. Polyphenols tell you what survived. Dates tell you how long ago. Ask for all three.
Our acidity figures
We publish the lab values for our oils, including K232 and K270, together with the harvest and bottling dates, so the bottle stops being a guess. Our free acidity figures are:
- Memilon BIO Crete: 0.18% in its lab analysis, under a quarter of the extra virgin limit. A certified organic, early-harvest Koroneiki that we think of as a finishing oil, first.
- Memilon Crete: 0.29–0.31%. A 100% Koroneiki from Phaistos in the Messara plain, cold extracted below 27°C (80°F), with 610 mg/kg polyphenols.
- Memilon Lesvos: 0.29–0.35%. A rare Kolovi variety from Plomari, elegant, balanced and delicately fragrant, with 512 mg/kg polyphenols.
All three sit well under half of the permitted maximum. That tells you the fruit was handled with care. Flavor, polyphenol levels and freshness are separate questions, which is why we publish those details too.
How to use this when you buy olive oil
- Treat acidity as a minimum standard. Anything at or below 0.8% can be extra virgin, and the best oils are far lower.
- Look for the harvest date, not just a best-before date.
- Ask for K232, K270 and polyphenol values, or a lab report for the batch.
- Taste it. A fresh extra virgin should smell of fruit, grass or herbs, and leave a little pepper in the throat.
Once you have a good bottle, use it where you can taste it, for example in a Greek salad done right or on a Cretan dakos.
What is the pH of olive oil? Is olive oil acidic?
Olive oil does not have a meaningful pH. pH measures hydrogen ions in a water-based liquid, and olive oil is a fat that contains almost no water, so a pH meter has nothing to read. That is why the acidity on a label is given as a percentage of free fatty acids, not as a pH number.
In the everyday sense, olive oil is not acidic either. It does not taste sour, and it is nothing like vinegar or lemon juice. A higher free acidity points to damaged or old fruit, not to a sharper flavor.
Frequently asked questions about olive oil acidity
Does low acidity mean a better-tasting olive oil?
Not directly. Acidity has no taste. It tells you the fruit was healthy and pressed quickly, which is a good starting point for flavor, but taste depends on variety, harvest time and freshness.
Is olive oil acidic like vinegar or lemon juice?
No. Free acidity is a percentage of free fatty acids in the oil, measured in a lab. It is not related to pH or to a sour taste.
What acidity should extra virgin olive oil have?
By law, 0.8% or less. Careful producers are usually well below that. Our published lab analyses range from 0.18% to 0.35%.
Can an olive oil with low acidity still be poor quality?
Yes. Refined oil can have almost no free acidity, and an old or oxidized oil can still pass the acidity test. That is why peroxide value, K232, K270, the sensory panel and the harvest date matter too.
Does acidity change over time?
It can rise slowly as an oil ages, especially if it is stored warm or in bright light. Another reason to look at the harvest date and to keep the oil cool and dark.
Where can I find the acidity of an olive oil?
Some labels print it, and a producer's lab report for the batch will show it. We list it for every oil on the product page, and you can check the acidity of your batch by its LOT number.
From our range
If you want to taste the difference careful handling makes, start with Memilon BIO Crete, our organic Greek extra virgin olive oil from Crete, for finishing, or Memilon Crete, a high polyphenol Greek olive oil from Crete for everyday use. You can browse all of them in our Greek olive oil collection. Shipping is free on every order.
Sources
- Commission Delegated Regulation (EU) 2022/2104 on marketing standards for olive oil: grades and limits for free acidity, peroxide value, K232 and K270.
- International Olive Council: trade standard for olive oils and olive pomace oils.
- Our own batch analyses: look up the lab results of your bottle by its LOT number.
