Bajo Aragon olive oil production is made with an exceptional care, respecting production times. To make this exceptional olive oil we can follow two methods. The method we are going to describe is the continuous method. This is the most modern to make olive oil. 


With this method olives have to be grinded the same day they are harvested, otherwise, as olives have vegetal water, this ferments and olive oil oxidizes. It is necessary to indicate that the olives storage time spoils notably the quality of the final product..



Process to elaboration olive oil with continuous method.

Description of the olive oil production process


                1. Olives storage: Olives harvested in the same day, are kept in transpirable boxes waiting to initiate the grinding process. With this method olives have to be grinded the same day they are harvested, otherwise, as olives have vegetal water, this ferments and olive oil oxidizes. It is necessary to indicate that the olives storage time spoils notably the quality of the final product.


                2. Olives washing: The process begins with olives wash in a washer installed in line with the rest of the plant, in which olives enters the washing vat, where a bubbly water current eliminates the stones and impurities that olives could have. Stones and other impurities are unloaded of the washer  automatically . The washing water is submitted to a recycling process in order to eliminate the dirt taking advantage several hours of the quantity of initial water in closed circuit, this way, diminished the consumption of clean water. In this point olives are qualify for qualities or varieties to obtain the best oils.


                3. Olive transport to the mill: Olives, once clean and drained, are transported to the mill with a elevator or not end screw. 


                4.  Milling: consist in crushing olives to obtain a paste composed for a solid part ( formed for vegetable and tissue rests) and other liquid, oil and water. This process is very important. With the continuous method olives grinding is made with a hammers mill with a star shape and endowed with interchangeable extra-hard tungsteno steel heads. The grinding size is regulated for the perforation diameter of the sieve, which turns in the opposite direction of the hammers. A dragging system assures the paste evacuation contained in the chamber, so clogging and excessive resistances is avoided in the work process.



Mill of hammers of the continuous method

Hammer mills used in the continuous method in the olive oil  extraction process.


                   5. Olives shaking: The olive paste shaking proceeding from the mill is made in a one or two horizontal bodies mixer made with stainless steel with chamber, for which warm water circulates for the chamber to get  warm.




Beater used in the continuous method for the elaboration of the olive oil

 Beater used in the continuous method for the olive oil extraction.



Olives paste falls to the beater where there are a stainless steel spiral blades that rotate with a studied speed to agglutinate to the maximum the suspended oil particles


Helical shovels for the elaboration of the olive oil.

Spiral blades that beat the olives paste to group the small oil particles



Tansport of the paste to the decanter is made for a helicoids spiral type bomb with specially adapted components for the extraction olive oil process. 

                6. Decantation: In this process the olive paste is separated in its  three components: oil, alpechín and marc. The decantation can be made to two or three phases.
With the two phases decantation, the obtained results are on one hand olive oil  and on the  other one the marc and alpechín, called alperujo. In this type of process water addition in the decanter  is not needed, with the consequent  decanter water saving and drinkable water and energy saving, and is obtained on the contrary, a very humid marc and with viscosity and lack of firmness characteristics that make it of difficult manipulation.


With the three phases decantation, is obtained in one side olive oil and alpechin, in the other side marc with a approximate humidity of 50%. With this procedure, additional hot water is demanded, but this way, we obtain dry and easy to manipulate marc oil.




Movement of the olive oil

In this image it is possible to observe the olive oil the decantation


The centrifugal horizontal decanter, has a cylindrical bowl and a endless screw, with the hollow axis, that turns in the interior. Due to the centrifugal force, the mass goes to the walls of the bowl and forms three strata of different densities:



                                            - marc( solid residues),

                                            - olive oil 

                                           - alpechín ( vegetable water).



Marc is evacuated for the endless, oil and alpechín spring from orifices placed to different levels, this process is called a decantation to three phases. With this system the water contribution is from 80 to 100 litters of water for every 100 Kg of olives. 


                7. Marc transportation: the unloaded marc from the decanter is collected in a transporting endless screw  that takes it to a storage chute of this product placed in the exterior of the oil-mill.


                8. Vibrate filter: Olive oil and alpechin pass for a few  vibrators sieves that retain the solid particles in suspension. The obtained oil is transported by means of a bomb of the vibrate filter  to a vertical centrifuge.


                9.  Oil cleaning and centrifuge: With a automatic vertical cleaning centrifuge machine, where, with the centrifuge force and inside of a plates rotor, proceed to its cleaning and eliminates its humidity, solids and impurities.


Once centrifuged, olive oil stays dissolved to be poured to the storage deposits. If the production process is made in three phases, that is to say, with alpechines production, another vertical centrifuge makes the revision in order to recover small quantity of oil that the above mentioned waters could contain before the dumping, dumping that generally is made passing for a decantation and with a adequate control that allows to avoid rivers and lagoons contamination.  

In the centrifugalization process the olive oil is cleaned of the impurities

Olive oil centrifuge machine. Used to clean, eliminate humidity, thin solids and impurities. 



                10. Electricity switchboard: It serves for the plant propelling, engine protection and other control elements like process temperature , production and energy consumption. 


                11. Storage and olive oil bottling: Clean olive oil is stored in stainless steel tanks. to avoid it from getting rancid or to get muddy this deposits have to be made with inert, opaque and waterproof material and do not have to absorb smells. Also the temperature has to be around 15ºC. 



deposit to store the olive oil

Olive oil tank image, where olive oil is stored to be later introduced in the bottles.



                12. Hot water generator: Is a small hot water generator to generally solid fuel, produces the process warm water needs and heating for all the plant.


The continuous method to make olive oil, presents higher production, as a oil mill can treat 8000 olives kilograms per hour, 25% of this will become olive oil.


Source: Pieralisi España S.L.