Ethyl esters (FAEE): the fruit quality marker

In brief. Fatty acid ethyl esters (FAEE) measure the fermentation of the olives before extraction. They form when damaged, heated or heaped-stored fruit ferments and releases ethanol. The IOC/EU threshold for extra virgin is ≤ 35 mg/kg. A low FAEE signals healthy olives, harvested and pressed fast; a high FAEE betrays fermented fruit — even if acidity stays low. It's the anti-fraud "freshness" parameter that unmasks reclassified oils.

Ethyl esters are one of the most useful — and least known — parameters on a certificate of analysis. Where acidity and peroxide can stay deceptively good, FAEE reveals whether the olives fermented before pressing. Here's what it measures and how to use it when buying in bulk.

What are ethyl esters (FAEE)?

Fatty acid ethyl esters are compounds that form through esterification between the oil's fatty acids and the ethanol produced during olive fermentation. The result: the more the fruit has fermented, the more the oil contains. The result is expressed in milligrams per kilogram (mg/kg) on the COA.

This fermentation appears when olives are bruised, heaped-stored too long, heated or poorly ventilated between harvest and mill. Yeasts and micro-organisms then turn the fruit's sugars into alcohol. FAEE is therefore a marker of the fruit's sanitary quality and of the speed of the harvest → extraction chain.

What does a high FAEE reveal?

A high ethyl ester level indicates fermented or degraded olives before extraction. It's often the sign of ground-fallen harvest, prolonged storage in jute or heaps, or too long a delay before pressing. The oil may then show the "muddy/winey" sensory defect on the panel.

The point that makes this parameter valuable: an oil can show compliant acidity and peroxide while having an out-of-threshold FAEE. That's why ethyl esters are considered an anti-fraud tool: they unmask medium-quality oils presented as extra virgin, or "cold-deodorised" oils meant to mask defects.

The FAEE threshold by grade (IOC/EU)

Here is the maximum ethyl ester threshold set by the trade standard of the International Olive Council (IOC/T.15/NC) and European Union regulation. The parameter concerns above all the extra virgin grade. Reference data, to be verified against the texts in force.

Grade	Ethyl esters (FAEE) max	What it means
Extra virgin (EVOO)	≤ 35 mg/kg	Healthy fruit, fast extraction
Virgin	Not capped in the same way	Wider sensory tolerance
Lampante	—	Degraded fruit → refining

Key point for EU export: FAEE is among the criteria Brussels introduced precisely to make the extra virgin grade reliable and combat reclassified oils. An oil that exceeds 35 mg/kg cannot be marketed as EVOO in the EU, even if all its other figures are good.

FAEE, acidity, peroxide: don't confuse them

These three parameters measure different things. Combining them avoids nasty surprises:

1. Free acidity → enzymatic degradation / hydrolysis of the fats (≤ 0.8 % EVOO).
2. Peroxide value → primary oxidation, freshness of the oil (≤ 20 mEq O₂/kg EVOO).
3. Ethyl esters (FAEE) → fermentation of the fruit before extraction (≤ 35 mg/kg EVOO).

An oil can pass the first two and fail on FAEE: it's the typical scenario of olives stored too long but pressed "cold". To read a whole certificate line by line, see our guide how to read a COA, or try the quality classifier that cross-checks all the thresholds.

How to use FAEE when buying in bulk

• Insist on FAEE on the COA. It isn't always reported by default: request it explicitly, from an IOC-accredited laboratory. (See our quality process.)
• Cross-check it with the panel. A high FAEE and a "muddy/winey" defect flagged on the panel confirm fermentation.
• Beware of "borderline" values. An oil at 33–34 mg/kg passes as EVOO on paper, but leaves little margin. A clearly low FAEE (≤ 15 mg/kg) is a better guarantee of healthy fruit.
• Use it as an anti-fraud filter. On a batch whose acidity and peroxide are perfect but the price suspicious, FAEE helps you decide.

Tunisian oils extracted cold soon after harvest — Chemlali (South/Sfax) and Chetoui (North) varieties — commonly show FAEE well below the threshold when the harvest-to-mill chain is short.

FAQ — Ethyl esters (FAEE)

What are ethyl esters in olive oil?

Ethyl esters (FAEE) are compounds formed by the reaction between the oil's fatty acids and the ethanol from olive fermentation. Their level, expressed in mg/kg on the COA, measures the fruit's sanitary quality and the speed of extraction.

What is the FAEE threshold for extra virgin olive oil?

The IOC/EU threshold is ≤ 35 mg/kg for extra virgin. It's a maximum: the best oils, from healthy fruit pressed fast, sit well below it. Above it, the oil cannot be classified as EVOO in the EU.

What does a high ethyl ester level reveal?

A high FAEE indicates fermented or degraded olives before extraction: ground-fallen harvest, prolonged heap storage, heat. The oil often shows a "muddy/winey" sensory defect. It's a warning signal, even if acidity stays low.

Can FAEE be good while acidity is bad (or vice versa)?

Yes, because they measure different things. Acidity reflects hydrolysis of the fats; FAEE, fermentation of the fruit. An oil can have compliant acidity and an out-of-threshold FAEE — hence the value of reading both together.

Why is FAEE an anti-fraud parameter?

Because it detects medium-quality or fermented oils presented as extra virgin, including "cold-deodorised" oils meant to mask defects. The EU introduced it to make the EVOO grade reliable.

Does FAEE always appear on the COA?

Not systematically: it isn't always reported by default depending on the laboratory. For a bulk export purchase, request it explicitly, from an IOC-accredited laboratory, and analyse each batch.

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Importing bulk olive oil? Request a quote: each batch is delivered with its full COA (acidity, peroxide, K232/K270, ethyl esters, polyphenols) from an accredited laboratory. For all the technical vocabulary, see the glossary.