Producing the oil [available also in italian]
The olives, after they have been harvested, must immediately be taken to be crusher, so as to prevent the
fermentation of the flesh, which is one of the principle cause of low quality in olive oils.
The process of obtaining the oil can be summed up in four phases:
Crushing: by crushing (or milling) is meant the process of pulverising the olives so as to break up the flesh
from which the oil will subsequently be extracted. Among the most common models of olive presses are
the hammer type, in which rigid rotating structures crush the olives, hitting them against a perforated
Kneading: the olive paste from the mill is subjected to another operation before being pressed to extract
the oil. By the term ”kneading” is meant a gentle stirring, at a controlled temperature, of the olive paste.
In this way the volume of the paste is reduced and the emulsions of water and oil formed during the
crushing are broken down, thus favouring the subsequent extraction of the oil The kneaded olive paste
is highly perishable and must be worked on as soon as possible to make sure it does not oxidise.
Pressing: we thus come to the most important operation, that of the actual extraction. The classic system,
that is most widely used and still today the most effective, is extraction by pressure. In brief, it involves
subjecting the kneaded paste to pressure in such a way as to favour the release of the oil and the vegetable
water ("must") which thus separates from the solid part (the "residues").
Centrifuging: a centrifuge effects the separation of the vegetable water from the oil. Centrifuge separators
are based on the principle that oil and water have a different specific gravity, and this makes it easy to obtain
an oil which has to be decanted only once to be absolutely ready for storing. The clarified oil, that is an oil
which is free of grease or vegetable water but not necessarily clear, must be stored in opaque glass, out of
the light and not exposed to excessive temperatures.