We rarely question the making process of something as natural as olive oil, but as I did for the cheese, I will go through the steps of its making process.
Obviously the first one is Harvesting:
Olives are taken from the tree, they can either be hand-picked or using some machine (shakers).
Then the Olives are stored in large buckets or bags.
Best Olive Oils require that Olives are transported to the mill just after harvesting. This is to avoid the development of a bad taste due to the dirt and to keep the freshness of the olives.
Leaf Removal & Washing:
Olives are then put through grids so that their twigs & leaves are removed and then they can be washed!
So now the real process can start! Once again Best Olive Oil require that the olives are crushed within 24hours after harvesting!
The olives are crushed with their stone by using Stone Roller, Hammermills or Metal Tooth Grinder (the last one is not commonly used).
They are malaxed (stirred & mixed) until they become a homogenous paste.
The next step is to separate the liquid from the solid part. There are different ways of doing it as you will see below. Olive Oil makers can use one or the other or can combine them:
The Traditional method: Pressing
The olive paste is spread on big disks then they are stacked on top of each other to be pressed. The pressure will make the liquid flow on the side of the disks. This liquid doesn’t only contain oil but also some vegetable water, it needs to be separated…
The Modern Method: Centrifugation
The paste is put into a spin in a horizontal drum. The solid part being heavier than the water & oil, it is attracted to the outside, and leave the liquid in the centre of the drum.
The percolation or Sinolea method
A comb or some blades of metal are dipped into the paste, the oil will naturally cover them, and then a machine will rack the oil off them. This method is quite expensive due to the limited amount of oil extracted on each blade.
The last step is to separate the oil from the water present in the fruit. This is not required all the time as some centrifuge will have this function already included in the machine itself. However, after a traditional pressing, it is needed most of the time.
Separation using gravity is almost not used anymore, as it is costing a lot of time and staff. The liquid is put into a tank, by gravity the oil will come to the top, to be then manually removed…
The method that is mostly used nowadays is a vertical centrifuge, due to the difference of density between the water and the oil, they separate!
Then the olive oil is transferred into a tank to be bottled up....