Olive oil is popularly considered as “olive juice“, and while being technically so, its manufacturing is much more complicated than common juice production. The oil drops are contained inside the vacuoles of the olives, in the mesocarp, so to extract the juice from them it is essential to break the drupes and then separate the oil from the other components of the olive.
There are two systems which can be followed to extract the oil from the olives: the so-called traditional or discontinuous method, and the modern or continuous one. It is important to keep in mind that olive oil extraction is mechanical, while seeds oil are mainly extracted by chemical process. For more information on the differences between the traditional and modern methods read the full article.
How is olive oil produced? Here is a quick guide.
Olive Oil extraction phases
We’ve already mentioned the two different methods of extraction: the traditional (or discontinuous) process, and the modern (continuous) one. To produce a high-quality EVO Oil some phases are performed in the same way in both methods (harvesting, leaves removal and olive washing), while others differ in practice (crushing, malaxation, extraction), as different technologies and methods are applied in the two processes.
To produce a high-quality EVO oil it’s essential to choose the perfect harvesting time, which usually is at the beginning of the so-called veraison phase, when the olive drupe colour begins to turn from green to black, and olives contain the maximum concentration of polyphenols and pigments. To preserve drupe’s integrity, hand-picking is usually the perfect choice among others, despite being the most tiring and time consuming one!
Because of that, and in order to have all olives picked up at the same stage of ripening, large cultivations utilize a mechanical system instead. It’s fundamental to avoid the collection of the olives already dropped on the ground (like in the so-called “raccolta da terra”): oxidative processes start immediately when the olive detach from its branch; as a result, every defect developed during this time will then also be transferred to the oil.
Therefore, once collected, the olives must be carried to the mill as soon as possible, where they are left inside ventilated containers for a maximum of 24-48 hours (closed bags are to be avoided, to preserve the integrity of the olives and prevent the formation of mold and microrganisms).
Leaves removal and olive washing
Through this phase, dust, soil traces and twigs are removed from the olives. Crushed leaves are not dangerous (on the contrary, they donate green pigments to the oil), but they may confer a too bitter and sour connotation to the final product, so they should be present in minimal part.
Pitting and Crushing
Olives are full of enzymes (e.g. peroxidases, lipoxygenases) which – each according to its own nature – can either contribute to improve EVO Oil quality, or destroy healthy components (e.g. polyphenols). Peroxidases are one of the main enzymes involved in phenols degradation and are highly concentrated in the olive pit, so it’s easy to understand how pitting can help to improve EVO quality.
To crush olives, the traditional process establishes the use of presses such as granite stones used in an open air space, while in modern systems metal crushers are used in closed controlled machines, in order to reduce the presence of air and oxygen which may have a bad impact on the quality of the olive oil produced. The result of this phase is an “olive paste“, not yet an “olive juice” or olive oil. The “olive paste” must then be worked up to separate the oil from the other solid components (referred as pomace).
The goal is to keep blending the olive paste obtained from the grinder to facilitate the aggregation of the micro oil droplets into bigger ones, and thus helping the following process of olive oil extraction. In this stage, enzyme functions are essential for the production of EVO Oil aromas. This is also a critical phase in terms of avoiding oxidation, which is directly correlated to time, temperature and oxygen contact.
The actual extraction of the oil from the olive paste is made by mechanical pression when following the traditional (discontinuous) method, or by centrifugation in the modern (continuous) system. The result of this phase is a mixture of olive oil and water. A crucial difference between the discontinuous and the continuous method lies in the exposure of the olive paste to air, which is harmful to olive oil quality. The traditional or discontinuous method carries out the process in open air, while the continuous one avoids the exposure to oxygen. To know all the differences in the two processes, read the article.
The blend is centrifuged to separate the olive oil from the residual water.
Filtering is not required but highly recommended, as it eliminates contaminants (sludges) like olives fragments or enzymes which may create sediments, and represent the ideal environment for microorganisms growth and chemical or enzymatic degradations. When filtering is done correctly, could improves olive oil shelf life.
Before bottling, olive oil may be kept in stainless steel tanks closed with nitrogen, to avoid any contact with air and oxygen.