The excellent olive mill that we use only tests your oil’s acidity level. This is a crucial quality indicator; to be classed as ‘extra virgin’ the oil must have an acidity level of 0.8% or lower. The lower the level the higher the quality. Ours ranges from 0.1% (highest possible quality) to 0.3% (still amazing).
However the mill doesn’t test the polyphenol levels. We would have to send a sample to a lab and the cost is £200. Expensive but not extortionate. But we would need to test every single pressing which would mean around 10 samples increasing the cost to £2,000. Out of the question!
So here’s a guide to evaluating olive oil’s polyphenol level yourself . . .
Your sensory experience provides powerful clues about an olive oil’s phenolic content. The distinctive sensations you feel when consuming high-phenolic olive oil directly correlate with specific beneficial compounds:
The throat burn phenomenon That distinctive burning sensation in your throat comes specifically from oleocanthal, a powerful anti-inflammatory compound. Scientists have discovered that this sensation uses the same sensory pathway as ibuprofen, which explains why both create similar throat responses.
This burning is your body’s recognition of potent medicinal compounds—not a quality defect.
Bitterness intensity The pronounced bitterness in high-phenolic olive oil comes primarily from oleuropein and its derivatives. These compounds have demonstrated powerful antioxidant and blood pressure-regulating properties in clinical studies.
Taste profile evolution Unlike lower-quality oils, high-phenolic olive oils evolve on your palate:
- Initial grassy or fruity notes
- Mid-palate bitterness development
- Delayed pungency and throat sensation that intensifies over 10-30 seconds
The more pronounced these characteristics, particularly the delayed throat sensation, the higher the likely phenolic content.
Understanding how olive oil is produced helps explain the vast differences in polyphenol content:
Timing Early-harvested (green) olives contain up to 80% more polyphenols than fully ripened olives
Speed Immediate processing after harvest preserves polyphenols that degrade with time
Method Hand-harvested olives typically suffer less damage, preserving more polyphenols
The highest phenolic oils combine early harvest, immediate cold processing, and proper storage—practices that require significant expertise and investment. True high-phenolic olive oil costs significantly more to produce because:
Early harvesting yields up to 80% less oil per olive
Specialised processing equipment maintains lower temperatures
Small-batch production limits economies of scale