Fatty acid ethyl esters (FAEEs) are one of the analytical parameters used to classify extra virgin olive oil. They do not measure the same phenomenon as free acidity or peroxide value: they can provide information mainly about fruit quality and fermentative changes affecting olives before or around processing.
In brief
- In the EU, EVOO must contain ≤ 35 mg/kg FAEEs.
- High values are associated especially with poor-quality, damaged, overripe or fermented olives.
- Consumers cannot measure them at home: laboratory analysis is required.
- A low value is positive but does not by itself prove EVOO status; all chemical and sensory criteria must also be met.
What are ethyl esters?
FAEEs can form when ethanol reacts with fatty acids. In virgin olive oil, ethanol is closely linked to fermentative processes in the fruit, which is why FAEEs are useful markers of olives that may not have been in optimal condition. Research also shows that cultivar, fruit condition and post-harvest handling matter, so the number should never be interpreted in isolation.
What is the EU limit?
Commission Delegated Regulation (EU) 2022/2104 sets a maximum of 35 mg/kg for EVOO. The same legal framework also requires compliance with free acidity, peroxide value, K232, K268/K270, ΔK and sensory criteria.
Why can FAEEs rise?
Fermentation before milling
When olives remain for too long in conditions that favour microbial activity, ethanol production and FAEE formation can increase. Experimental work has observed increases in some cultivars after prolonged room-temperature fruit storage.
Damaged or overripe olives
Mechanical damage, overripeness and poor post-harvest management can favour changes in the pulp. This does not mean that one bruised or ripe olive automatically makes an oil non-compliant: the extent of damage and management of the whole batch matter.
Can you taste ethyl esters?
Not quantitatively. Fermentation may generate sensory defects detectable by a trained panel, but the FAEE concentration in mg/kg requires laboratory analysis. Sensory assessment cannot replace the chemical test.
How are they measured?
Official and validated procedures use laboratory separation followed by gas chromatography. There is no reliable home test equivalent to the official determination.
Consumer checklist
- Read FAEEs together with acidity, peroxide value, UV indices and the analysis date.
- Do not treat very low acidity as a complete guarantee of quality.
- Remember that EVOO classification also includes official sensory requirements.
FAQ
Does 35 mg/kg mean the oil is extra virgin?
Not by itself. It is the EU maximum for this parameter, but all other requirements must also be met.
Are ethyl esters simply a sign of old oil?
No. They are strongly linked to fruit quality and conditions and may also evolve during storage; they must be interpreted in context.
Are FAEEs the same as acidity?
No. Acidity measures free fatty acids; FAEEs are esters formed with ethanol.
Conclusion
FAEEs are an important part of EVOO evaluation because they help reveal what may have happened to the olives before extraction. Their value is greatest when interpreted together with other chemical parameters and official sensory assessment.