The market for machinery for the extraction of extra virgin or EVO oil from olives requires innovations that make it possible to increase yields and, at the same time, preserve the quality of the oil.
The malaxing is the phase in which numerous transformations, of a mechanical, physical, chemical and biochemical nature, desired and unwanted, take place simultaneously and in a sufficiently long period of time so that the control conditions are scarcely reproducible, also due to the rhythms of work. convulsions linked to the brevity and intensity of the oil campaign.
But kneading is also the part of the process that modulates the quantity / quality of oil production: its correct regulation allows to obtain the best yield / quality ratio of the product.
The pressing determines the breaking of the drupe into coarse fragments containing hundreds of cells.
These must pass intact through the mechanical device. Cell rupture is not pushed to the extreme in consideration of two factors negatively linked to a possible surplus of mechanical energy. In this case, in fact, there would be an increase in the temperature of the paste which would compromise the quality of the oil with the consequent risk of emulsions that would damage the extraction yields.
In the traditional olive oil extraction process, to extract a surplus of oil it is necessary to extend the kneading times or, alternatively, to increase the process temperatures. However, this choice could compromise the quality of the product especially if oxygen is present in the head space of the malaxer; in this case oxidation processes can in fact be triggered by the unsaturated fatty acids with a consequent decrease in polyphenolic substances and consequent reduction of the organoleptic characteristics of the product.
The long kneading times, in addition to being a threat to the quality of the oil, make this phase of mixing and processing the oil paste at a controlled temperature the “bottleneck” of the continuous process.
In the mill, the limited working capacity of the malaxer penalizes the production efficiency of the decanter.
Currently, the main plant engineering solution adopted to manage this “inefficiency” consists in multiplying the number of kneaders, placing them in series or in parallel, ensuring continuity to the process but with a significant increase in the investments required in the mill. While, the improvements obtained by experimenting vertical malaxers, the use of atmospheres composed solely of nitrogen to lengthen the malaxing up to an hour and a half or the addition of natural micro talc or the addition of specific fluidifying enzymes even if they actually increase yields of up to 3% significantly increase energy and production costs as well as the need to install a large number of additional malaxers to avoid further bottlenecks.
Correctly managing the flow of the production process leads to enormous advantages in terms of efficiency and a reduction in costs, especially in terms of energy.
It goes without saying that the strengthening of the weak link of any process must be such that the advantages obtained with the innovation are greater than the costs that the innovation itself requires.
By acting on macroscopic variables such as time, temperature and composition of the atmosphere in contact with the olive paste, the biochemical reactions that occur simultaneously with the physical process of coalescence of the minute droplets of oil released in the pressing are modulated and determines how much and what quality of oil it will be possible to extract.
However, it is known that extraction yield and oil quality are antithetical values and that, therefore, any operational choice made with the machines currently present in the mill requires a choice that favors quality or quantity.
It is therefore necessary to develop a process that is able to carry out a delicate breakage of the cells passed intact to the crusher, avoiding emulsions and unwanted temperature rises, accelerate the coalescence phenomena (physical phenomenon through which the drops of a liquid join together to form larger entities) of the minute droplets of oil released by the elaioplasts (the leucoplasts specialized in storing lipids), allow the dissolution of the biophenols from the aqueous fraction of the olive paste towards the oily fraction and favor the enzymatic synthesis of the volatile compounds while limiting the oxidation reactions of fatty acids.
All harmonized in a system that can operate continuously, transferring the oil paste from the crusher to the decanter without recreating bottlenecks that penalize the latter’s working capacity.
After careful analysis and research, mature technologies capable of guaranteeing the improvements required in the process have not been identified in the agri-food sector.
To obtain them it is necessary to adopt technological innovations initially designed for other areas; among these, controlled cavitation represents the trump card to eliminate the bottleneck that was created due to the weak link in the continuous extraction process of extra virgin olive oil thanks to the effects that this induces within the same pasta oil during processing.
When conditions arise that lead to cavitation of a fluid, when negative pressure values are below the vapor pressure of the fluid itself, it undergoes a phase change from liquid to gas, forming cavities containing vapor and giving rise to the phenomenon cavitation.
Therefore cavitation is a physical phenomenon consisting in the formation of vapor bubbles inside a fluid that are formed not by an increase in temperature, but by pressure variations, these implode producing shock waves, i.e. pressure waves that can be extremely intense. If the implosion occurs near the cell wall of the drupe, it generates micro jets that break the wall, releasing the contents of the cell, all within a few microseconds.
