OIL EXTRACTION PROCESS
HARVEST
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Before the actual harvest there are 12 months of care and maintenance of the trees in order to achieve a healthy and abundant harvest.
The process of formation and accumulation of oil in the fruit is called “lipogenesis”, and it is tremendously influenced by agroclimatic factors. Determining its achievement, and therefore, the optimal time of collection requires expertise, experience and use of the laboratory.
From this first moment it is necessary to make a commitment to quality, because here we face several factors that are not completely compatible with each other, such as: obtaining a healthy and quality product, obtaining the greatest amount of oil possible and causing the least possible damage to tree during harvest.
In our drive to achieve excellence we proceed to the following type of collection:
- 1- Early harvest, when the tree offers the greatest amount of olives in veraison and we find the maximum percentage of polyphenols and volatiles to have the opportunity to produce Extra Virgin that can express the complex range of organoleptic qualities.
- 2- We collect the olives using mechanical methods (“grape harvester” in the superintensive and “umbrella” for the traditional olive grove) and only fly olives.
- 3- The transport to the oil mill is done with great care and in a few minutes due to its proximity to all our olive groves. Immediately upon arrival of the olive we begin the production process, itself. Not giving rise to waiting or storage.
PATIO OPERATIONS
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They include receiving the fruit, unloading, cleaning (with or without washing) and weighing the fruit.
Once the quality of the fruit has been verified, the download begins. This is done through a grate in the pit receiving hopper, built in stainless steel and with a 0.5 meter 3-sided plinth. This plinth protrudes from the ground, preventing pollutants from falling into the hopper and vehicles passing over it. From this precise moment, the entire journey of the fruit to the preservation of the oil in the cellar will be made on food bands and stainless steel. For the sake of better cleaning we have discarded all kinds of augers for the transport of the olive paste, opting for different types of pumps for its transport.
Subsequently, the olive goes to the cleaning compact where leaves, small branches and stones are removed. We have the possibility of washing the olives, a decision that will be made based on the need for it. The process continues with continuous weighing and from here to the hopper prior to grinding.
The extraction process of a high quality Extra Virgin Olive Oil is complicated due to the variability of the olive, even though it is of the same variety and from the same place, its properties can vary from day to day in terms of humidity, percentage of oil and pulp, forcing to continuous corrections in the extraction process.
Our extraction system is Cold Extraction by 2-phase Centrifugation. Also known as ecological centrifugation since we have lower water consumption and without the problem of vegetable water.
This process can be divided into three large blocks:
- Preparation of the olive paste. It encompasses the Grinding and Shaking of the pasta
- The Solid-Liquid separation that is currently carried out by the Decanter, is about extracting the oil from the alperujo
- Liquid-Liquid extraction takes place in the vertical centrifuge cleaning the oil and eliminating moisture, impurities and any remaining fine solid that may have remained.
GRINDING
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The objective sought in grinding is to break the vegetable tissues of the fruit to release the oil contained in the vacuoles of the mesocarp, giving rise to the olive paste that will be made up of pulp, stone, oil and vegetation water.
This operation is carried out by means of a stainless steel rotating sieve hammer mill. We will take special care in certain aspects of the process:
- Achieve uniformity in the pasta (to facilitate subsequent mixing).
- Obtain a suitable degree of grinding (average particle size). If it is very thick we will not have sufficiently broken the cells that contain the oil and if it is too thin we will obtain porridge from which it is very difficult to extract the oil. The degree of grinding is achieved thanks to the screens that are grids with perforated holes in different sizes. Generally, the campaign begins with smaller diameters (4-5 mm) and increases as it progresses in time until sieves of 6-7 mm.
- Avoid overheating the paste due to friction.
- Adjust the speed of the mill to aerate the paste as little as possible.
THERMOBATED
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By beating we seek to form a continuous oily phase, agglutinating the dispersed drops of oil in the paste. For this we make use of the mixers, tanks inside which paddles rotate at a constant speed whose mission is to circulate the pasta and put the oil drops in contact. These tanks are heated by means of water that circulates through a double wall.
At Alguijuela we have a blender with 3 independent bodies each, with a capacity of 600 kg per body, thermal panoramic glass, self-cleaning and water addition system and a comprehensive equipment for temperature control.
We are at the most critical point in the process. Again, we must combine two opposing factors Quality vs Quantity and for this we have 3 parameters to control:
- Blade Rotation Speed: If the blade rotation speed is excessive, the paste will aerate too much, increasing oxidation. If, on the other hand, it is too slow, the movement of the paste will be insufficient.
- Blending Time: An excess of blending time produces a decrease in polyphenols and therefore a greater instability of the Oil. A short time may be insufficient for the small drops of oil to coalesce into larger drops.
- Pasta Temperature: It is clearly demonstrated that the increase in temperature leads to better use in the extraction (Quantity), but in the same way negatively affects the Quality of the oil obtained.
To get the best EVOOs, Cold Extraction is necessary. Cold Extraction Extra Virgin Olive Oil is considered to be that which has been extracted at a temperature lower than 27 degrees Celsius.
Temperature has a great impact on the quality of the oils. The aroma of these is due to volatile substances, therefore, at a higher temperature, more volatile ones evaporate and thus lose the oil in aromas and flavors. In addition, cold extraction helps reduce the oxidation rate of the pasta, thus obtaining oils with less acidity.
SOLID-LIQUID EXTRACTION
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The separation of solid and liquid phases is done by centrifugation in two phases, using the Decanter or also called “continuous extractor”. The decanters are solid-jacketed horizontal helical centrifuges. These separate into phases according to the different densities of the products.
In our case it will create two phases:
- Near the axis it gets the light phase that is the oil.
- On the back, next to the wall of the cylinder, it separates the alperujo (the solid phase composed of pulp, ground bone, vegetation water …, forming the mass called alperujo).
The alperujo is collected in containers that are removed by companies in the sector for subsequent treatment and use. The oil obtained by the Decanter is collected in a vibrofilter, which removes the solids that it may carry in suspension and from there it is transported by means of a non-emulsifying pump to the vertical centrifuge.
LIQUID - LIQUID SEPARATION
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This separation is carried out in vertical centrifugation, by means of centrifugal force and inside a rotor of saucers, the oil is “cleaned”, eliminating the humidity and the remains of fine solids and impurities that may have remained.
At 6,200 revolutions per minute, the centrifugal force separates the liquids in a drum (oil and water) with a minimum power of 2.2 kW. The water comes out through a rear conduit of the machine and the oil through a wide mouth in the upper front part, being ready for passage to the winery.
CELLAR
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To keep the EVOOs produced in our facilities in perfect condition, the oil is kept in stainless steel tanks, with a lower load and with a conical bottom to facilitate its “bleeding”, that is, the removal of moisture and impurities that decant over time. and being located at the bottom of the tanks being responsible for fermentation.
The tanks are of different capacities (10,000 lt, 5000 lt and 2500 lt) being in a dark environment and at mild and constant temperatures.
PROCESS CHART
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