Obviously, olive oil quality will depend on olive quality to a great extent.
According to the European Union legislation (Regulation EC 1019/2002), there are four categories of olive oils
Extra virgin olive oil: Superior category olive oil obtained directly from olives and solely by mechanical means. This oil’s taste and odour are unbeatable, free of faults. Its percentage of oleic acid(acidity grade) must not be over 0.8°.
There are three types of extra virgin olive oil: the one that comes from a single variety of olives; the so-called Coupage, a blend of different varieties of olives, and P.O.D oils, produced with olives from a certain territory, which have been manufactured and bottled there.
To obtain the qualification of extra virgin oil, this kind of oil must obtain a 6.5 organoleptic qualification in an assessment by a certified pairing panel.
Virgin olive oil: the grade of acidity can reach 2º and the scoring of the pairing committee must exceed 5.5 points. It follows the same processes than extra virgin olive oil.
Olive oil: olive oil non-described as virgin or extra virgin is an oil product of a combination of refined olive oils. When oil does not pass the quality tests to be considered as virgin or extra virgin olive oil, it must be submitted to a refining process. The acidity grade of this olive oil cannot exceed 1.5°, as this oil is not pure.
Olive-pomace oil: oil comprising exclusively oils obtained by treating the product obtained after the extraction of olive oil and oils obtained directly from olives. The grades must not be more than 1.5°.
There is another category called lampante virgin olive oil, previously used as fuel for oil lampsbecause it is not suitable for human consumption. Nowadays it gets refined to obtain refined olive oil, but when it is not mixed with virgin or extra virgin olive oil at least at 30% it is not suitable for human consumption.
To prepare this low-quality oil, we use olives from the ground and those frozen, pitted, etc.