How to Choose Real Extra Virgin Olive Oil

In 2016, the University of California Davis Olive Center tested 186 olive oils sold in California as "extra virgin" and found that 69% of imported samples failed International Olive Council (IOC) extra virgin standards. Similar investigations have been conducted in the UK, with comparable results.

The reasons are varied: oils pressed from damaged or overripe olives that do not meet chemical standards; oils that were extra virgin when pressed but have degraded before reaching the shelf; refined oils blended with a small percentage of EVOO and labelled deceptively; and mislabelled geographical origin.

This is not universal — plenty of genuine, high-quality extra virgin olive oil is sold in the UK. But the label alone is not sufficient. Here is what to look for.

The single most important piece of information on an olive oil label is the harvest date — the year the olives were pressed. This is different from the best-before date, which typically runs 18–24 months from pressing and tells you almost nothing about current polyphenol content.

Olive oil polyphenols degrade from the moment of pressing. An oil pressed in October 2023 that is still on a supermarket shelf in September 2025 has lost a significant proportion of its polyphenol content, regardless of storage. The flavour may still be acceptable, but the health properties will be diminished.

Look for the current harvest year. In Italy and Sicily, olives are typically pressed in October to November. Oil from the 2024/2025 harvest year is current stock. Oil with no harvest date printed — only a best-before — is a yellow flag: the producer is not confident the provenance will stand scrutiny.

"First cold press" or "cold extracted" on the label means the oil was produced at below 27°C using mechanical means only, without added heat or chemical solvents. This is a legal requirement for the EU extra virgin designation, but it should be stated explicitly.

High temperature extraction increases oil yield per kilogram of olives — typically 20–30% more — which is economically attractive. But heat degrades polyphenols, chlorophyll and volatile aromatic compounds. The extra oil is nutritionally inferior.

"Cold extracted" should appear on any quality EVOO. If it is absent, the extraction temperature may have been higher than the legal EVOO maximum, or the producer has not bothered to make the distinction.

"Product of Italy," "Product of Greece" or "Packed in the EU using oils from the EU and non-EU countries" are insufficient origin statements for a quality olive oil.

Genuine single-estate or regional EVOO will name the specific location: a village, an estate, a grove. Castruriali states Castroreale, Messina, Sicily — a specific hill town with a specific mill (the Mandanici family mill, operating for over 70 years). This level of traceability is a commercial risk for the producer — if the oil is not what it claims to be, the claim can be checked.

Vague "Italian olive oil" or country-of-origin blends are not necessarily bad — but they cannot provide the provenance or batch-level traceability that genuinely high-quality single-estate EVOO offers.

Light accelerates the oxidation of polyphenols, chlorophyll and fatty acids in olive oil. Clear glass bottles are the correct packaging for olive oil only if they are kept in the dark at all times — which supermarket shelving under fluorescent light does not permit.

Genuine quality olive oil producers use dark glass (typically dark green or amber), opaque metal tins or black glass specifically to protect the oil from light degradation. This adds cost and reduces the retail appeal of showing the oil's colour — which is a compromise quality producers accept because they know the oil's longevity depends on it.

A premium olive oil in a clear glass bottle on a well-lit shelf is not being handled correctly, regardless of the quality of the production.

A genuine high-polyphenol extra virgin olive oil will taste peppery at the back of the throat (oleocanthal) and slightly bitter on the sides of the tongue (hydroxytyrosol, oleuropein). Both are positive attributes in EU olive oil regulations and in professional sensory evaluation.

If you open a bottle labelled "extra virgin" and it is mild, buttery or neutral with no pepper and no bitterness, one of three things has happened: it was pressed from very ripe olives (low polyphenols), it was pressed at high temperature (polyphenols degraded), or it has aged significantly (polyphenols oxidised). In any case, the health properties associated with extra virgin olive oil in research will be minimal.

This is not a matter of taste preference — it is a biological marker. The pepper and bitterness are the polyphenols you are buying.

The best producers will show you their laboratory analysis. Polyphenol content, free acidity and peroxide values can all be measured and published. This removes any ambiguity about what you are buying.

Castruriali's 2024/2025 harvest has been independently verified: 410mg/kg total polyphenols, free acidity ≤0.30%, peroxides below 2 meq O₂/kg. The full certificate is available at castruriali.com/info. If a producer cannot or will not show you their lab results, treat any polyphenol claims with scepticism.