Virgin Oil Extraction
The olive tree is a typical tree from the Mediterranean basin because it requires great light and a climate characterized by soft winters, rainy autumns and springs and hot and dry summers.
The growth of olive trees is slow. It generally blooms after 5 to10 years since the plantation and reaches its full maturity 20 years later. Its maturity and full production period goes from 35 to 100-150 years. After that, the tree gets old and its production becomes irregular.
1. Fruit collection
The olive tree blooms in spring and the fruit starts to grow and mature, changing from green to black, from summer until the end of autumn/beginning of winter when it is harvested.
The olive harvest can be done by hand (“ordeño”), through (“vareo”) hitting the tree with long and flexible poles so that the olives fall onto prepared canvas covers placed on the ground or by mechanical vibration.
2. Transportation to the oil mill
The collected olives are transported to the oil mill (mill) to be ground. It is important to say that those olives, collected from the ground ,which must be transported separately, with the help of nets, must be free from stones, ground or dirt to avoid possible skin breakages during transportation causing the beginning of unwanted fermentation.
Once at the oil mill, the olives must not be piled up to avoid heating and fermentations. To obtain a high quality oil, the olives must be processed within 24 hours after being harvested.
3. Washing
The olives in the conveyor-belt go through a ventilation area where an air flow separates the fruits from the leaves. The olives are washed in running water after being selected according to quality.
4. Grinding to prepare the paste
The grinding consists of the fruit squeezing (without separating it from the pit) until it becomes a paste that is later whipped, adding water if needed.
5. Solid and liquid phase separation (oil extraction)
There are several methods, but in neither case, the temperature rises above 35ºC.
Traditional System (by pressing)
Discontinuous Classic Plants
These are the classic plants maintained through centuries. The ground paste is placed between pressing mats and is subject to pressure to expel the oil must (mixture of oil and water). This is allowed to rest so that density difference comes into play, separating the oil from the water.
Continuous System (by centrifuge)
Continuous Plants in 3 phases
The whipped olive paste is added 1 liter of water per kilo of paste and it is added into a horizontal centrifugal machine, where the solid is separated from the oil must. Then, the must is passed on to a vertical centrifugal machine, where the olive oil is separated from the vegetable water.
Continuous Plants in 2 phases
The process is practically the same as above but instead of adding water for the horizontal centrifugation, the vegetable water is recycled.
The continuous system, which is more and more widespread, presents the following advantages in comparison with the traditional system:
- higher production capacity, avoiding the storage of olive and improving the oil quality
- improvement in the performance, cleanliness and hygiene
- in the 2 phase plants, the vegetable water recycling provides a higher polyphenol quantity in the oil, natural protectors against oxidation.
6. Storage
The oil obtained is stored in cellars until it is ready to go to market.
The walls and roof must isolate high temperatures and must prevent strange odors. The ideal temperature is between 15 and 18ºC to allow oil maturity without favoring oxidation. There must be light brightness.
The material in which they are deposited must be inert (glass-coated tile, stainless steel, polyester -fiber-glass, etc.) Iron and copper must be avoided since they favor oxidation.
Non-virgin Oil Extraction
Refining
Due to climate conditions, type of soil and flaws in the previously described process, sometimes, virgin oils present defects such as extreme acidity, strange color and odor, etc. This oil is not suitable for human consumption (called "lampant oils"), so it must go under a process to eliminate such defects. There are two types of processes:
1. Classic alcalin refining
It consist of 3 phases, each of them tend to eliminate a certain process:
-neutralization
-decolorization
-deodorization
2. Physical refining
It differs from the previous process in the use of acid water, instead of salted water, to purify the oil. It also differs in that the temperature used is higher.
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