Olives from different plantations are ground to paste using millstones (traditional method) or steel drums (modern method) at room temperature.
The paste is spread on disks and these disks are kept one on top of the other.
The stack of disks is pressed using hydraulic press to extract oil.
This oil that is received only from physical processes (and without using heat or chemicals) is called Virgin Oil.
The first oil extracted from olives and when it is extracted within 24 hours of their harvest is called Extra Virgin Olive Oil.
But for virgin olive oil to be called extra virgin olive oil, it must have less than 1% of free oleic acid; virgin olive oil can have up to 2% of free oleic acid.
If a certain oil has been extracted using only physical means but contains oleic acid up between 2% & 3.3%, it is called Ordinary Virgin Olive Oil.
Anything above 3.3% is considered Lampante Virgin Olive Oil and is not fit for consumption and must be refined using high temperatures and chemicals.
After refining, olive oil is tasteless, colourless and lacks antioxidant qualities, so some extra virgin olive oil & antioxidants are blended to it; the result of this is Pure Olive Oil (since it only has olive oil and no other oil).
If a certain portion of vegetable oil is added to the refined olive oil, it is called Light Olive Oil (it is no longer pure olive oil); it has a high smoke point and is fit for high heat cooking.
After the virgin oils have been extracted, the leftover paste, called pomace is taken to the extraction plant.
Extraction process generates crude olive pomace oil, which is then refined using various chemical and heating processes; this refined oil is called Olive Pomace Oil.
People are discouraged from using virgin oils for high heat cooking (above around 190 degree C) as they can produce harmful chemicals and burning makes them smell bad.
