Trasformation: milling and extraction

Once in the oil mill, the olives undergo several processes. The first one is defoliation, during which the olives are cleaned from each external element such as little branches and leaves, that can endanger the machineries in the following stages. We have to remark that only 1% of the olive amount can be constituted of leaves and little branches. Too many leaves and branches can produce a green bitter-sour oil.

Next phase is washing. It's useful to increase the quality of the oil. In this stage of the process, rotten olives and mud are eliminated. According to national and european laws, drinkable water is to be used in the washing.
Milling is the next phase. It is operated through big grindstones or by several mechanic processes.
Grindstones allow a slow and regular milling, without any considerable temperature increase. Moreover, there are machines that utilize modern technologies, and therefore implement the working process. However, these modern processes produce an oil with a bitter taste, resisting to oxidation.

Although, there have been several attempts to combine the two processes and the most effective one is the Hadria mill. This kind of system has the task to avoid the overheating of the paste and , at the same time, to reduce considerably the working time. It is formed by a pre-milling system, a collecting basin, a low revolutions plate mill. It produces a very good oil.

The cleaning of the machines themselves is very important, because remainders could fermentate and therefore endanger the correct production of oil.
In the next phase the oil is shaked to obtain bigger drops that will be detached during the process of centrifugation. In this phase, the temperature of the paste (no + 40°), and the cleaning of the machines are crucial.

Then, there is extraction. It offers a long list of pros and cons. The traditional system, the pression system, requires great caution when applicated to a 24 hours working cycle. The plates on which the paste is disposed should in fact be continually cleaned. Only so, the oil produced can reach a high quality rate. The other system is the one that uses the percolation process. Through it , 50-60% disoleation can be obtained. Its great working capacity has always had to face skepicism about this system because of the great amount of water required by the old decanters. Recently, however, some technological innovations have been introduced to escape these problems.

The last phase is clarification, that takes place through a centrifugation process. It has the function to separate water in the oil-must, that has to be "veiled" at the exit from the separator.