Learning about extra virgin olive oil > La Trasformazione del Prodotto

After the harvesting operations have been completed in the best possible way, it is just as important that the olives are transported with every care and as soon as possible to the mill: the weight of the heaped-up drupes causes bruises in the fruits at the bottom, with the consequent attack of moulds and fermentation may begin.

It is necessary, therefore, that the olives are transported in well-aired baskets, and that they are milled in the shortest time possible.

Before proceeding to the extraction phase, the olives undergo some important operations: automatic aspirating machines separate them from residual leaves and impurities; then they are washed with forced-circulation water, which eliminates the vegetable and mineral residues and impurities.

At this point the olives are ready for the most important operations which have been repeated, almost immutably, for thousand of years: crushing and scutching are the two operations through which, one after the other, we obtain olive paste which will then proceed to actual crushing.

Crushing literally means breaking: in this phase, in fact, the olive pulp and kernels are completely torn up through an energetic treatment, performed by the muller or by the more modern and faster hammer-crushers. From this first phase we obtain a coarse mass, still containing chopped pulp and kernel fragments, which have a draining function, and facilitate the separation of the liquid part of the paste from the solid part.

The paste thus obtained at this point is mixed slowly in the scutching machines, so as to break up the water-oil emulsions which have formed during crushing and so that the droplets of must-oil come together in bigger and bigger drops.

The characteristics and procedures of these initial phases have remained almost intact over the centuries; above all the materials used in mills have changed, and now stainless steel, used for the fact that it remains intact and is easily cleaned, has taken the place of granite and wood.

After separating the oily must, the next phase is actual extraction, which leads to the final separation of the three components of the paste, which are husk oil, vegetation water and oil.

There are various methods of obtaining a final product, each of which has been perfected thanks to the experience accumulated over the centuries.

These can roughly be grouped into two types, discontinuous or continuous. The most traditional system, extraction using mechanical pressure, can be placed in the first type. Here the paste is placed on vegetable fibre discs (baskets (fiscoli) which nowadays are more often made of synthetic materials and which are gradually piled up under the press, where the increasing pressure, over about an hour, presses out the oily liquid component  - must oil). The solid part, which sticks to the baskets, is husk oil.

Continuous methods, nowadays prevalent, have substituted for pressing other physical principles which lead to the separation of the oil from the solid part. The system of extraction by centrifugation, for example, which exploits the different specific weight of each single component, give rise first to the separation of husk oil and liquid part, and thereafter isolates the oily component of the vegetation water.

Another clever and hygienic method, percolation, exploits the different surface tensions of oil and vegetation water: through the rhythmic immersion of stainless metal blades in the olive paste, the liquid which adheres to their surface is progressively gathered. With this system from 60 % to 70%  of the oil contained in the olive paste is extracted; the rest is separated from the residues of skins and kernels by centrifugation.

At the end of these operations, the oil obtained, notwithstanding the method, is cloudy and opalescent and contains mucilage in suspension, air bubbles and residues of atomized water. A period of rest is necessary to ensure that extraneous substances do not become deposited on the bottom (decantation). The next process is decanting.

Besides this system, the product can also be filtered, a process which confers the limpidity and brilliance that we know, and prevents particles of vegetable matter from quickly turning the oil rancid. At this point the “new” oil is ready to be sent to shops and supermarkets.

back to learning about extra virgin olive oil