Olive Oil is produced by crushing the olive fruit including the stone into a paste and then extracting the oil from it. There are two ways of doing this: the traditional method using grindstones for the crushing and churning of the fruit and means of pressure to extract the oil; and the modern method using large mills to transform the olive fruit into paste and centrifuges for oil extraction.
For an easy understanding of the process of the olive oil production, we will be looking at the traditional method.
- Either process starts with the olive harvest. The farmer needs to be attentive and observe the right moment with the correct stage of maturity, taking all due care during the harvest not to damage the fruits.
- Once garnered, the crop is fed into the mill, where stalks and leafs are removed for the following stage – washing.
- Next, grindstones proceed to crush the olives (stones included) and obtain a mass that is a mixture of solids (pulp, skin and stone), and liquids (vegetal water and olive oil).
- Now, the mass obtained (olive paste) in the crushing is pressed at room temperature between natural fiber mats, thus separating the solids from the liquid.
- The liquid then undergoes decantation, by which the olive oil ends up floating in the denser water. Once fully separated, the water is drained off to leave the oil.
- Once the oil has been obtained, it is classified by specialist tasters making an initial degustation and then sending it to a lab for further tests regarding the acidity.
The remaining solid mass after pressing might be further processed because it still contains a small amount of oil. It cannot be extracted by further pressing and is therefore submitted to a chemical process in a plant using solvents. The resulting oil (no longer olive oil!) is called pomace oil in the United States.