The working cycle

The working cycle of our and your olives

OleificioThe working cycle of our and your olives follows a rigorous process where also the overtures are very important. The warehousing represents a prominent overture, because the quality of the extracted product depends on the final processes that are greatly subordinate to the preservation state of olives and to the waiting period before the grinding. The preservation in big heaps with an insufficient ventilation and slow waiting period cause some fermentation processes of olives that determine a worse quality of the olive oil.

This phenomenon becomes more noticeable in the case of traumas during the harvesting or of the attack of oil fly (bractrocera oleae).

For this reason in our system, the preservation of olives is executed in perforated bins situated in an airy room and the grinding is made in 48 hrs from the harvest of olives. Our oil-mill has two transformation lines marked Pieralisi, that have a production capacity of 55 quintal per hour and run a cycle of continuous manufacture in three phases. Each line is equipped of an harvesting tub connected to a conveyor belt that place olives into a water tubs called lavatrici, which keep water in forced movement to improve the result of operation.

After that olives pass over a contained tub from which, trough a closed cochlea (machine screw), rise inside an olive-press (hammer olive-press at low-acting: 1400 revs per minute). From this spout an olive paste that goes to a kneading tub where take place the first separation. This phase last less than 40 minutes and the temperature is at least 27° C. The result is a cold extraction, that guarantees the conservation of chimical-organolectic features of extracted oil.

Later on the paste pass inside an horizontal axle separator, called decanter, from which leak sansa, oil must (containing water) and vegetation water (containing a little deal of oil). These two quantities pass trough a vertical separator and here take place the definitive separation and the leak of olive oil.

Detailed description of working processes

The olive oil manufacture goes trough three phases: frangitura (the olive-press), gramolatura (the kneading) and estrazione (the extraction).

The olive press

The olive press is the first phase of real extraction. Olives are subjected to mechanical processes that cause a breaking of the cell wall and of the membrane with a leaking of cell juice and oil. The hammer olive-press is the favourite instrument of modern system at continuous cycle because it perfectly adapts to the automation needs of the system. An hammer olive-press is composed by a series of revolving disc equipped with hammers with a rotation speed of 1300-1500 revs per minute. Thanks to this system, the leak of pulp and stone is caused by blows of high speed revolving devices and just in part to mechanical action of stone fragments. The manufacture takes place in short time, after that the oil paste, always mechanically, is spilled inside beneath kneading tubs. The olive-press phase represents a very important passage in olive manufacture. The important of this phase depends of olive-press, because during the leaking of cell wall, enzymes enable both in pulp and in seed which act over chemical components of oil. The various enzymes stimulate the release of volatile substances, responsible for the aroma, feature that give to the olive oil his peculiar tastes: fruity, bitterness and spicy together with the conservation of the same oil: the polyphenols.

The kneading

The kneadingis an operation that follows the olive press and consists in breaking the emulsion between water and oil and flowing together oil micelles in bigger drops which aim at part from water. It takes place in kneading-machines called gramole and it really represents the first phase of oil extraction. The gramola is a steel tub with spinning blades that roll at 20-30 revs per minute preserving the mixing of the oil paste (flotation). The mixing breaks the emulsion improving the oil must productivity in the following phase of extraction. And also this process is important for the conservation of the chemical-organoleptic features. The quality of olive oil is guaranteed by: the contact with the oxygen, the temperature and the manufacture duration. The excessive contact with the oxygen of the oil paste forms particular substances called peroxydes and the oil aims at the degradation during the conservation period. The degradation of oil means the loss of the organoleptic features (fruity, spicy and bitterness), caused by the reduction the polyphenol numbers. It is important remember that peroxyde content is in inverse proportion at the polyphenol content, so larger is the quantity of peroxydes in our oil, smaller is the polyphenol content and vice versa. The manufacture temperature affects the productivity of the following phase, the extraction, and it is closely related to the stability of the water-oil emulsion. In fact, with a low grade of emulsion, the kneading takes place in an environmental temperature (from 22-24°C to 27°C), and in this case it is called cold extraction. With stable emulsion it is necessary heating the paste, with temperatures above 27°C, but always lower than 30°C. This is the limit of a quality olive oil because the productivity increases with the kneading temperature, but in this level, the paste suffers a quality decay:

  • Taste worsening (warming and metallic flavour)
  • Loss of volatile substances and fruity taste
  • Smaller diet properties caused by a loss of polyphenols, tocopherols and A vitamins.

For this reason, the warming doesn't have to surpass 30° C. The kneading takes place during 30-40 minutes, not longer than 60 minutes. The protraction of the manufacture operation doesn't weigh upon the rendering of oil, but it is better to avoid it because the contact between oil paste and air determines a bigger oxidation.

The extraction

It consists in the separation between oil must (skins and pulp fragments) and the sansa (solid fraction constituted by stone fragments). The type of extraction made in our system is called three phases centrifugation extraction. This is a common and quality method. It enables to ride out disadvantages of the pressure extraction (worse quality of olive oil owing to difficulties of cleaning filter screens, considerable costs for labour and functioning at discontinuous cycle). After the kneading, the oil paste thanks to particular pumps, pass trough pipes at an horizontal centrifuge. This pushing process represents an important point to keep the chemical-organoleptic qualities of olive oil. To push the oil paste within pipes, the pumps use a great deal of water giving to oil paste a bigger fluidity. On the contrary an excessive water amount, could cause a placer mining of the polyphenols contained in the paste, and the oil would be pale, smooth without polyphenolic charge. Then it is subjected to a centrifugation in the decanter (a rolling conical drum at horizontal axis). For effect of the different specific gravity, the centrifugation separates three fractions (three phases separation):

  • the sanse (olive residues);
  • the oil must, containing a small deal of water;
  • the vegetation water, containing a small deal of oil.

The oil must and the vegetation water are conveyed in a further separator, where undergo an other centrifugation that separates water residues from the first one and oil residues from the second one. This type of separation is called vertical centrifugation and this is the most used system (with the exception of Sinolea extraction) to separate oil to water fraction.

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