The first step in making the oil is to crush the fruit. This is what used to be called 'pressed'. Once the fruits have been crushed, the semi-solid paste is dropped into the next machine (see video.)
We're looking down into the metal blade grinding trough which turns the crushed the olives into a paste. The purpose of crushing is to tear the flesh cells. This releases the oil from the vacuoles. In olden times, this part was done with large stones.
The machine then churns the paste over and over. In olive oil extraction, this is called malaxation (from the Latin malaxare, Greek μαλακος meaning "soft"). It's the action of slowly churning or mixing milled olives, typically for 20 to 40 minutes. The churning allows the smaller droplets of oil released by the milling process to aggregate and be more easily separated. The paste is normally heated to around 27 °C during this process. Cold pressed (extra virgin) oils must not exceed 27˚C at any step in the processing of the oil.
WARNING! The paste can be heated to higher temperatures or water added during this process to increase the yield, although this generally results in lowering the quality of the oil. At this mill no water is added so what you're seeing is pure olive paste.
One of the problems for buyers of olive oil is knowing whether the oil really is extra virgin olive oil. Sadly, many olive oils labelled as extra virgin are not what they purport to be. Reasons for lower quality can be:
> oxidation by exposure to elevated temperatures during malaxation, to light, and aging oil;
> adulteration with cheaper refined olive oil; > poor quality oil made from damaged and overripe olives, processing flaws, or improper oil storage.