Many of you who are not familiar with the processes of olive oil, and oils in general, may be wondering about how it is made. In fact, olive oil extraction is a process that counts several thousands of years! But before you learn about how let’s take a trip into history. Initially olive oil was produced in households around the Mediterranean (Greece, Spain, Italy, Morocco, etc.). Each family produced the quantity of olive oil it would need and to this end, they used stone vessels (mortars) where the olive fruit was simply crushed and heated. With the development of the first olive mills, the fruit was manually crushed. Olives were placed on large stone plates where pressure was exercised by a round-shaped stone. Then, olive paste was transported to the presses. The base of a press was a large, shallow basin made of stone, of a round or rectangular shape. Pressing took place with the use of a stone weight that was placed in the edge of a wooden beam, which was pulled downwards.
Later on, and specifically in the ancient Greek period of time, the fruit was crushed with a rotary mill. This type of mill consisted of two millstones with curved external surfaces, having two thick wooded beams by wich the millstones were manually rotated.
Nowadays, olive oil extraction has been industrialized with the use of modern technology and machinery, and has become a production chain, with discreet steps, each one with high importance. These steps include first of all the cleaning of the fruit and the remove of the stems, leaves and other debris left from the harvest, so that the fruit can be taken to the grinding step into the paste. The purpose of crushing is to tear the flesh cells to facilitate the release of the oil from the vacuoles. Next follows malaxing (mixing) the paste for 20 to 45 minutes, which allows small oil droplets to combine into bigger ones, an indispensable step for the formation and concentration of the oil. The last step consists in separating the oil from the rest of the olive components. This used to be done with presses (hence the now somewhat obsolete terms first press and cold press), but is now done by centrifugation, except in old facilities. Some centrifuges are called three-phase because they separate the oil, the water, and the solids separately. The two-phase centrifuges separate the oil from a wet paste. In most cases, the oil coming out of the first centrifuge is further processed to eliminate any remaining water and solids by a second centrifuge that rotates faster. The oil is then left in tanks or barrels where a final separation, if needed, happens through gravity. This is called racking the oil. Finally, the oil can be filtered, if desired.
