Delicious Italy has visited a number of frantoi across central Italy and Liguria on our travels and seen close up how cold pressed extra virgin olive oil is produced. Although we do not consider ourselves experts, there a 3 distinct processes.
The first is the 'frangitura' which breaks up the olives into a generous paste. The second is the 'gramolatura' where the paste is stirred well to prepare it for the actual extraction of the oil. The final stage is the said extraction.
Traditionally, the first two stages were achieved using millstones which crushed the olives to a pulp, perhaps driven by water wheels. The remains were then placed inside straw 'innertubes' and further crushed to extract the oil.
Today, water, centrifugal force and complex filtering systems are used to extract the oil, even by the most romantic of family establishments.
The secret of a good olive oil seems to be based on the principle of 'rubbish in, rubbish out'. Once picked the olives must be turned into the paste as quickly as possible to retain the inherent goodness, and all producers are aware that oxidization is the principal enemy of a good oil.
From the little we have picked up, such terms as 'extra virgin' and 'spremuta fredda' (cold pressing) are no real guarantee of a good olive oil.
The only absolute symbol to rely on is the DOP mark, but then again there is always fine olive oil being made locally for local consumption. Seek it out.