Olive oil extraction

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Olive oil extraction is the process of extracting the oil present in olive drupes, known as olive oil. Olive oil is produced in the mesocarp cells, and stored in a particular type of vacuole called a lipo vacuole, i.e., every cell contains a tiny olive oil droplet. Olive oil extraction is the process of separating the oil from the other fruit contents (vegetative extract liquid and solid material). It is possible to attain this separation by physical means alone, i.e., oil and water do not mix, so they are relatively easy to separate. This contrasts with other oils that are extracted with chemical solvents, generally hexane. The first operation when extracting olive oil is washing the olives, to reduce the presence of contaminants, especially soil which can create a particular flavor defect called "soil taste".

People have used olive presses since Greeks first began pressing olives over 5,000 years ago. Roman olive presses survive to the present time, with a notable collection present at Volubilis in Morocco. An olive press works by applying pressure to olive paste to separate the liquid oil and vegetation water from the solid material. The oil and vegetation water are then separated by standard decantation.

This basic method is still widely used today, and it is still a valid way of producing high quality olive oil if adequate precautions are taken.

First the olives are ground into an olive paste using large millstones at an oil mill. The olive paste generally stays under the stones for 30‑40 minutes. This has three objectives:

Olive oil mills very rarely use a modern crushing method with a traditional press.

After grinding, the olive paste is spread on fiber disks, which are stacked on top of each other, then placed into the press. Traditionally the disks were made of hemp or coconut fiber, but in modern times they are made of synthetic fibers which are easier to clean and maintain.

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