"Extra virgin" reads on the shelf like a promise of quality, but technically it is a grade, and the grade is defined by numbers. If the claimed grade and the measured values do not agree, the label is wrong — even where there is no bad intent.
The three axes that set the grade
- Free acidity: shows how far the oil has degraded chemically.
- Peroxide value: tells how far oxidation has progressed.
- Sensory assessment: determines whether defects are present and how fruity it is.
The three are judged together. An oil with low acidity but a sensory defect cannot reach the top grade even if it passes the numeric threshold. Looking at the laboratory result alone is therefore misleading.
A grade changes over time
This is the point most often skipped. The grade is measured after harvest, but the oil keeps oxidising through its shelf life. An oil that was extra virgin at bottling may not be six months later if it was stored badly.
A grade is not a title once earned; it is the state at the moment of measurement.
A brand that carries a grade claim therefore has to record distribution and storage conditions as well as the measurement at bottling. The question asked in an audit is not "what grade did you bottle" but "what grade is the oil in this bottle".
Purity is a separate question
Grading measures the quality of the oil, not whether it is olive oil. An oil blended with seed oil can look like a top grade with low acidity and good sensory values. Purity is a separate measurement and does not substitute for grading.
What pushes the grade down
Extra virgin is not a grade won once and kept. Oil keeps changing after harvest: light, heat, oxygen and time all raise free acidity and peroxide value. Every month in storage is a period that has to be managed for the grade to hold.
So the grade is the result of the product's journey, not of a single analysis report. Oil that was extra virgin at filling can end up contradicting its own label after six months in the wrong conditions.
Where adulteration hides
Adulteration usually sits not where taste or colour breaks down but precisely where nothing is noticed at all. Dilution with refined oil is not easily caught by the senses, which is why measurement belongs alongside a sensory panel.
- Colour alone is not a grade indicator; it shifts easily in light.
- Bitterness and pungency are quality markers, not faults.
- Cloudiness relates to filtration, not to purity.
- Dark glass extends shelf life but does not raise the grade.
The buyer's only lever
A buyer cannot audit the producer's store or the harvest conditions. Their one lever is being able to measure at the moment of delivery. Once measurement moves to the point of purchase, negotiation rests on technical ground: the discussion runs on a number rather than on trust.
The grade is won at harvest, held in storage and proven at the point of purchase.