How is olive oil made?

Madrid |
knocking down olives
Knocking down olives

As we’ve already learned on our post How to use, buy and store olive oil, olive oil should be thought of as the juice from a fruit. As with any other fruit, there needs to be a harvest as well as a process for extracting the juice from the fruit.

As a general rule, quality olive oils are harvested, extracted and stored on the same day. This means that during the harvest season, usually between November and March, olive oil is produced every day.

Step 1 – the olive harvest

Firstly, a big mat is laid out under the tree to catch the olives. Workers then hit the branches with long poles to shake the fruit from the trees, or some use special heavy machinery that vibrates along the trees’ branches.

Once the olives and leaves have fallen onto the mat, they are collected and carried to the oil mill by tractor.

oil olives harvesting
Oil olives harvesting
collecting olives
Collection with big mats
oil olives collection
Gathering olives in bags for transportation
loading tractor with olives
Transportation within the same farm
farm's olive oil mill
Farm's olive oil mill
collecting olives
Unloading in hopper

You can watch some short videos about each stage of the process, from harvesting to collection, and unloading to transporting the olives.

Step 2 - extracting the oil

Once in the mill, the olives are washed to remove any dust or dirt from the harvest, collection and transportation.

Once washed, the olives are separated from the stems and leaves. This process is manually supervised to ensure that no stones or rotten olives get into the mix.

Next, the olives are crushed in a hammer mill to produce smaller pieces of olive. These then go into a mixer to produce a paste which is then pumped into a decanter.

Finally, in the decanter the process of centrifugation is used to separate the oil from water and solid residue.

Visual inspection and crushing
Visual inspection and crushing
olives mixing
Mixer creates an olive paste
Olive oil decanter
Olive paste is decanted, not pressed

This physical process of crushing, mixing and decanting impacts the temperature of the paste, which then triggers chemical reactions (oxidation). The oxidation must be controlled to ensure a higher quality oil – the term “cold press” comes from the fact that the temperature is kept below 25º C during the mixing process.

And then you have a fresh, fragrant olive juice that is almost ready to be enjoyed.

Just left is the filtering and storing of the olive oil in stainless steel vats, very much like the ones used in wineries.

olive juice after decanting
Olive juice after decanting
oil filtering before storing
Olive oil filtering before storing
Olive oil decanter
Oil is stored in vats

Check out this video to see how the mixer works.

Step 3 - testing and analysis

Once the oil has been extracted from the olives, it needs to be categorized. This involves two steps – a lab analysis and a sensory analysis. The lab analysis looks for the presence of chemical compounds in the oil, while the sensory analysis checks other features such as smell and taste.

The most important indicator resulting from the chemical test is acidity, which is measured in degrees and equates to the percentage of free fatty acids in the oil. The lower the acidity, the better and for this reason “extra virgin” olive oil can’t exceed 0.8º acidity (0.8%). For the sensory test, the extra virgin olive oil must not have any defect in taste or aroma.

If the acidity is between 0.8º and 2º or the oil has little sensory defects, the oil will be categorized as “virgin” olive oil. That is, it is still a nice olive oil, but not as good as the extra virgin.

An oil with acidity higher than 2º or with severe taste defects will need to be refined to remove all defects – whether they are chemical or sensory. The result of the refining process is a liquid without color, smell or taste. It is just plain transparent fat in liquid form. This fat is blended with a small portion (10-20%) of virgin olive oil to recover the color, taste and aroma, which is then called plain “olive oil”.

olive oil classification
Olive oil classification

Note: This classification of olive oils is derived from the European Union, so it is applicable to all oils produced and marketed within the EU.

© Cooking Point, SL
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