1What do we mean by Acidity?
There is a widespread misconception: many believe that olive oil that "stings" in the throat is acidic. Nothing could be further from the truth! The peppery sting is due to oleocanthal, a powerful and highly beneficial polyphenol. A high-quality oil's acidity, on the other hand, cannot be tasted on the palate.
How it is measured
Acidity is expressed in grams of free oleic acid per 100 grams of oil and is measured exclusively through laboratory analysis. For an oil to be classified as "Extra Virgin," by law its acidity must not exceed 0.8%.
Acidity measures the state of degradation of the fruit: a healthy olive, picked from the tree and milled quickly, will produce an oil with minimal acidity (e.g., 0.1% or 0.2%). An olive that has fallen to the ground or was processed late will have much higher acidity.
The spiciness in the throat is not acidity — acidity is measured only in the lab, you cannot taste it in the mouth.