The cold pressing of olive oil

Extra virgin olive oil is a well-known gourmet element in our cuisine and also a key ingredient for our cardiovascular health. We all know it comes from olives, but how well do we know how the oil is extracted from the olive?

What is cold pressing of olive oil?

Oil’s cold pressing is the system used to extract the juice from olives, by separating oil and water that compose them. The extraction takes place, as the name suggests, using pressure. Once the olive has been harvested, it is crushed and kneaded to obtain a product known as “olive paste”. An oil with the “extra virgin olive oil” (EVOO) denomination must be extracted from the olive paste using only mechanical means (centrifuge machines), since the hot extraction process is the one used to get refined oils.
COLD PRESSING OF OLIVE OIL
COLD PRESSING OF OLIVE OIL

When an oil isn’t cold pressed?

The oil makes up between 15% and 20% of the olive paste. Heating this paste at high temperatures would favours the oil particles concentration and, therefore, their extraction. However, above 27º C the oil loses its organoleptic properties (flavour and smell) as well as the benefits for the consumers health.

Oil extraction systems

Cold pressed, the traditional system.

Traditionally, olive oil was obtained by introducing the olive paste between two mats made from esparto to which pressure was applied by metal plate means. The result of this process was a juice, made up of olive oil and water, which was allowed to flow into tanks where the oil was separated from the water by decantation. The different densities of water and oil made the latter occupy the upper part of the tank. However, this system became outdated due to:
  • Hygienic-sanitary reasons, since current food regulations advised against the use of this system for obvious reasons.
  • Economic reasons, since the yield was lower and the costs associated with its extraction made it extremely expensive.
This system had drawbacks that made the olive oil often present some organoleptic defects.
  • The esparto mats were requiring scrupulous cleaning after each use, since the organic remains that could accumulate in them were fermenting by bacterial action and transmitting smells and flavours to the new oil.
  • Contact with the ambient oxygen and with the water obtained from the decantation was initiating the oxidation process much earlier which, again, reducing oil’s properties.
  • This process was usually repeated two or three times, in order to obtain the maximum yield. This was making both the olive paste and the water start the fermentation process between each pressing, which was increasing oil degradation in each cycle.
esteras para prensado en frio de aceite
Oil cold pressing mats

Cold extraction, the current method

The use of more modern, clean and profitable extraction means has displaced the traditional system, which will remain as the oil’s history. Nowadays, we us centrifuge machines, which ensure the compliance of health regulations and help to produce an oil of the highest quality, free of impurities and oxidation processes as it’s not in contact with air. These centrifugal machines, also called decanters, use the density of each element present in the paste (oil, water, bone and skin) to proceed to its separation in a clean way, preserving all the oil’s properties. This centrifugation process is carried out in order to eliminate as much bone and skin particles – that can sneak into the process–  as possible. Even so, there are still small olive remains that are eliminated by filtering the oil and decanting it into storage tanks, ensuring that the oil reaches the consumer’s table in perfect condition.

Would you like to know an olive grove and the oil is produced?

Learn to recognise a high quality extra virgin olive oil, the olive cycle and all about Mallorca’s cuisine. Treurer is also a touristic emplacement in Mallorca based on oil production. Visiting to our farm will be quite an experience!
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