Obtaining virgin oils

The olive tree is typical of the Mediterranean area as it needs a lot of sun and a climate characterised by mild winters, rainy autumns and springs, and warm, dry summers.
Olive trees grow slowly. They usually bear fruit 5-10 years after they are planted and are not fully developed until they are 20 years old. They are most mature and fully productive between the ages of 35 to 100-150. After that the trees get old and their performance is irregular.

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Olive oil is obtained in the following steps: 
 
 1. Harvesting the fruit
Olive trees flower in spring and the fruit starts to form and then to ripen, changing from green to black, between the summer and the end of the autumn / beginning of the winter when harvesting takes place.
Olives can be picked by hand, or beaten from the trees (with long, flexible poles so that the olives fall onto the canvases placed at the foot of the trees), or harvested using mechanical tree shaking methods.

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2. Transport to the oil mill
The harvested olives are transported to the oil mill for grinding. Those that are collected from the ground with nets (and which have to be transported separately) must be as free from stones, earth and impurities as possible to avoid breaking the skin during transport, as this would lead to the beginning of fermentation.
On arrival at the mill, the olives must not be piled up high or else they will heat up and start to ferment. Olives must be processed within 24 hours after they are harvested to obtain quality olive oil.

3. Washing
On the conveyor belt the olives cross a ventilation area where the leaves are separated by an air current. They are washed with normal water after they are selected for quality. 

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4. Grinding to prepare the paste
Grinding consists of crushing the fruit (including the pits) until a paste is formed which is then beaten. Water is added if necessary.
 

5. Separation of solid and liquid phases (oil extraction)
There are several methods, but in all of them it is essential that the temperature does not exceed 35º C
 
Traditional system (pressing)
· Classic discontinuous plants
These are the classic plants maintained throughout the centuries. The ground paste is placed between round mats and is then pressed to squeeze out the oily liquid (mixture of oil and water). It is later left to decant, as the oil floats to the top due to density differences.

Continuous system (by centrifugation)
· Continuous plants in 3 phases
The beaten olive paste is made more liquid by adding 1 litre of water per kilogram of paste and is taken to a horizontal centrifuge where solids are separated from the oily liquid. This liquid is then taken to a vertical centrifuge where the olive oil is separated from the fruit vegetable water.
· Continuous plants in 2 phases
The process is practically the same as the one described above, with the difference that instead of adding water for the horizontal centrifugation, the vegetable water is recycled.
The continuous system is becoming more and more widespread and has the following advantages compared with the traditional system:
- high production capacity, which avoids having a stock of olives and therefore increases the oil's quality
- improves performance, cleanliness and hygiene
- in the 2 phase plants, recycling the vegetable water means the oil has a larger quantity of polyphenols, natural protectors against oxidation

6. Storage
The oil obtained is stored in cellars or warehouses until it is marketed.
The ideal storage room is a place where the walls and ceilings insulate against high temperatures and which does not add strange smells to the oil. The ideal temperature is between 15 and 18º C to allow the oils to mature without oxidation. There must not be much light.
The material of the storage containers must be inert (vitrified tile, stainless steel, glass polyester fibre, etc.). Iron or copper must never be used, as they encourage oxidation.
 
Obtaining non-virgin oils
Refining
Due to climate conditions, the type of soil and faults in the abovementioned process, virgin oils can have several defects, such as high acidity, a strange colour or aroma, etc. which makes them unsuitable for human consumption (they are called "lampante oils"). This means they have to undergo a refining process to eliminate defects. There are two types of processes:

1. Classic alkaline refining
This has 3 phases. Each one tends to eliminate a specific process:
-neutralisation
-bleaching
-deodorisation

2. Physical refining
It is different from the previous method as acid water is used instead of soda to purify the oil and the temperature is higher.

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