The acidity of the olive oil shows the condition of the olive fruit from which the olive oil was produced. It is a chemical parameter that measures the free fatty acids found in olive oil. These fatty acids are 'released' only when the olive fruit is damaged or attacked (eg olive fly, gloeosporium). If the olives are healthy, fresh and milled immediately after harvest, the fatty acid chains do not break and the acidity remains low (0.1-0.3%).
The production of free fatty acids is due to the lipolytic action of the enzyme lipase, which is found in the olive fruit. This action takes place mainly before the extraction of olive oil and therefore the acidity changes very shortly after its extraction from the olive fruit.
The acidity of olive oil can be detected only with chemical analysis and not with tasting. It is not the most important quality criterion because it is possible for an olive oil with low acidity to have a serious organoleptic defect. In that case, this olive oil cannot be characterized as Extra Virgin