Extra virgin olive oil is pure olive juice and is the only vegetable fat obtained using physical processes, never chemical, unlike olive oil and all other seed oils.
Olive oil is composed of 90-95% refined olive oil and 10-5% extra virgin olive oil. The only purpose of the refining process of olive oil is to eliminate the defects resulting from a series of errors during production, such as excess heat, late or faulty collection of the fruit, implying a greater yield per kilogram of olive and a loss of healthy organoleptic properties of the olive oil.
In order for olive oil to be classified as extra virgin a series of physicochemical and sensorial parametres established by the International Oil Council (IOC) need to be met. The chemical analysis measures the level of acidity, peroxide index and ultraviolet (K270) absorbency. The sensorial analysis values and scores the organoleptic properties.
There is no relationship between acidity and the intensity of flavour of an oil. It is a chemical parametre that determines the amount of free fatty acids in the form of oleic acid and has to do with the production process. High acidity points to abnormalities in the state of the fruit, its treatment or storage. According to the IOC the maximum acidity for EVOO is 1º.
The peroxides are indicative of the level of primary oxidation.
As regards sensorial parametres, an extra virgin olive oil has an irreproachable taste and aroma. If the slightest defect is detected is has to be marketed as Virgin Olive Oil (VOO). These slight defects (sour, fusty, rancid, humidity...) are not easily detected by consumers with no training in sensorial analysis.