It was formerly called pomace to the remains of olives after obtaining the virgin olive oils.
Pomaces were composed by the pulp, skin and bones, water, and a residual amount of olive oil, approximately between 2 and 3%. Currently, with the mills of two phases, the by-product obtained is called 'alperujo', and it is a compact mass formed by the same components and with olive oil in its interior in the same percentage.
To be able to extract this small amount of olive oil, chemical solvents are used, commonly hexane, and the procedure is performed in the orujeras (extraction companies) or extractors.
Obviously this is not virgin olive oil. Its name is raw pomace olive oil.
This pomace olive oil has the same fatty acid profile than if it had been removed by physical processes. However, like the lampante olive oils, they have acidity and some unpleasant aromas and flavors that do not fit for consumption, and therefore they have to be refined.
The raw pomace olive oil, once refined using the same process used with lampante olive oil, is called refined pomace olive oil, and like the refined olive oil, has no taste, no smell, no color; and is it not permissible for consumption.
Finally, and like the refined olive oils, refined pomace olive oils are mixed with virgin or extra virgin to provide them flavors, color and aromas. This final product, already acceptable for its consumption, is called pomace olive oil,which consumers can find in shops and supermarkets.
Here you can find out all types of olive oils and their origin.