Olive oil defects: how to recognise them in five minutes

Bitterness is not a defect. Nor is the tingle at the back of the throat. In fact, both are signs of freshness. A smell of old walnuts, wet cardboard or damp wood, on the other hand, means there is a problem.

Many people have tasted a defective olive oil without ever knowing it. They simply decided they did not like olive oil. That is a shame, and it can be put right. Learning to recognise defects takes about ten minutes.

A defect is not a matter of taste

In the world of olive oil, a defect is a precise notion. The International Olive Council has defined a list of negative attributes. Professional tasters, sitting as a panel, taste the oil blind from a blue glass and record what they perceive.

The rule is strict. A single defect perceived by the panel is enough for the oil to lose its "extra virgin" designation. The oil is downgraded. This is not a matter of personal preference: it is a measurement, just like acidity or polyphenols.

The defects you come across most often

Rancid

This is by far the most common defect. It comes from oxidation: the oil has been exposed to too much light, too much heat, too much air, or simply too much time.

You recognise it by a smell of old walnuts, dried walnut kernels, wax crayons, sometimes putty or fresh paint. In the mouth, the oil is flat. There is nothing green left about it, nothing alive.

Rancidity is the most frequent defect in home kitchens, quite simply because a bottle left open for eighteen months next to the hob always ends up there.

Fusty

A word you will hear nowhere else. It describes the taste of olives left piled up too long before being pressed. Deprived of oxygen, the fruit heats up and ferments.

The smell is heavy, slightly sweet and frankly unpleasant. Some describe it as fermented black olive, others as stagnant mud. It is the defect that best tells the story of what happens between picking and the mill. At our estate, the olives are hand-picked and cold-extracted the same day: fustiness has no time to set in.

Musty

Olives stored for several days in damp conditions develop moulds and yeasts. The resulting oil smells of cellars, mushrooms, forgotten laundry.

Winey

A note of wine or vinegar, sometimes slightly sharp on the nose. It comes from acetic fermentation. At low levels, some people mistake it for liveliness. It is nonetheless a defect.

Muddy sediment

It appears when the oil has been left too long in contact with its sediment, at the bottom of a tank or a drum. The taste becomes heavy, earthy, slightly dirty. This is also why a very cloudy oil is not necessarily a guarantee of authenticity.

What is not a defect

Three sensations are regularly mistaken for problems when they are in fact the hallmarks of a fresh, rich oil.

• Bitterness, in the middle of the mouth. It comes directly from polyphenols.
• Pungency, that warm tingle at the back of the throat a few seconds after swallowing.
• Coughing. In tastings, oils are even rated as "one cough" or "two cough". The more an oil makes you cough, the richer it is.

These three markers are linked to the oil's phenolic content. We cover them in detail in our article on polyphenols.

The five-minute test to do at home

1. Pour a teaspoon of oil into a small glass.
2. Cover it with the palm of your hand and warm it for about fifteen seconds. The heat releases the aromas.
3. Uncover it and breathe in deeply. Cut grass, tomato, artichoke, green almond: a good sign. Dry walnut, cardboard, cellar: a bad sign.
4. Take a small sip. Draw a thin stream of air in between your teeth, as if through a straw.
5. Swallow, then wait. The tingle should arrive within the next few seconds.

A tip: never rely on the colour. It depends on chlorophyll and on how ripe the olives were, not on quality. That is precisely why professional panels use an opaque blue glass.

Why "zero defects" matters

On a professional tasting sheet, the first line is not fruitiness. It is the median of defects. When it is zero, it means that not a single panel member perceived the slightest negative attribute.

This is the result achieved by our Skourochori cuvée at the 2026 organoleptic panel: zero defects. It is not a medal, it is a starting point. A defect score of zero simply means that nothing went wrong between the tree and the bottle: hand picking, cold extraction the same day, storage away from light.

We publish all our analyses, cuvée by cuvée, on our analyses page. Acidity, polyphenols, oleocanthal, pesticide residue screening. A serious oil can be verified; it does not need a story.

To go from theory to the glass, the Oikos Antalis cuvées are waiting for you among our bottles.

And if you would like to learn to taste by the book, with the blue glass and the full scoring sheet, that is the purpose of our masterclass L'Art de la Perception, co-led with Emmanuelle Dechelette.