To obtain quality olive oil, olives must be processed within 24 hours.
After picking, olives are taken to the olive oil mill (almazara) where they are first classified and washed with cold water to remove leaves, twigs and any other foreign body. After washing, the milling starts. To obtain quality olive oil, olives must be processed within 24 hours of harvesting. Olives are subject to a first pressing - without prior decoring - to extract the juice. Oil quality depends greatly on the subsequent processes. A good producer should watch these steps carefully.
Presently, three systems coexist to obtain olive oil:
- hydraulic presses
- continuous three-phase or output systems
- two-phase systems, ecological and with no production of alpechín (olive juice)
Approximately five kilos of olives are required to obtain one liter of first pressing olive oil.
The purpose of the traditional pressing process followed by decanting and the usual centrifugation is the extraction of the oil. The milling waste is a watery liquid called alpechin(or vegetable water) and a paste called pomace (orujo).
Several benchmarks help to define the olive oil quality. The most important are low acidity and the sensory characteristics (prompted by smell and taste), while pungent, bitter and fruity flavors are deemed as positive attributes.
Extra virgin olive oil.It is the highest quality oil. It meets all standards with regards to acidity, aroma and flavor.
Virgin olive oil.A quality oil but with a slight flaw. It does not require a refining process.
Olive oil.This is the name given to the blend of virgin olive oil and refined olive oil.
Refined olive oil.This is an olive oil that has had some important alteration of its natural characteristics and therefore it was refined, i.e. subject to a chemical process.
Olive pomace oil.This is the olive oil obtained from the waste of the first extraction (pomace) and that has been refined.