The transformation of olives into oil represents the end of the process of oil production, after the phase of bedding the tree.

Proceeding in the production of oil you need some precautions to have everything under control and above all to get high quality oil.

The process phases "since the harvest of olives to the bruschetta" (roasted bread with fresh olive oil) are the following: harvest, conservation, transport and washing; afterwards you start the processes of crushing, kneading, extraction, separation and conservation.

- Harvest: picking off the drupe by the tree, we shall surely use for the extraction olives that have not finished yet the process that leads to those enzymatic phenomena that make oil oxidated. One of the best harvesting systems for the quality of oil is the cutting off made by hand with the help of combs or other differently shaped devices that let drupes fall down on nets or shields placed on the ground. The "bacchiatura" (beating down) with canes or sticks and the harvest of olives fallen down on the ground thus mixing the recently fallen olives with the rotten ones are processes which is better to avoid.
- Conservation:the best one, ever since the harvesting from the field, is the conservation in tall wooden or plastic punched boxes (20-30 cm), that can be stored one upon the other and possibly in fresh, ventilated places, repaired by rain, wind, by risk of frosts and especially far from bad smells (stables, or gasoline); the conservation in racks is allowed but with a thickness not over 10 cm.

- The stay in the oil mill building: in this phase the worst danger are two: a - The olives stay too much inside the oil mill building and in an unsuitable way; b - quantities of sane olives are mixed with rotten ones or others in bad condition. To avoid these risks the olives should reach the oil mill according to a precise program in order to avoid useless stays.
- Washing: the olives must be ventilated to wipe dust, leaves and little branches away (the presence of any sane leaf does not threat the quality of the final product and give it a fresh, spicy taste, generally appreciated by consumers), then they are washed under cold running water to get rid of earth and foreign matters; eventually the passage across vibrating grids help in getting the water far and in separating olives from stones. A "cyclone-maker" before the washing tank allows to get all heavy matters far completely: stones, metallic matters or everything else that could cause serious damages to the engine. If you keep on washing you obtain the opposite effect that is the "smearing" of the olives.

The kneader absolutely is the machine where olive paste stays for the longest delay. So hygienic care is very important.

- Extraction: the man has always committed to extract oil from olives formerly by stone mullers that crushed olives inside basins (of stone them too) and enabled to obtain the must by overflowing. Then, during the following centuries, the process has slowly evolved by passing by mullers to mechanic crushers, by wood presses to presses formerly mechanic and eventually hydraulic; only recently we assisted to a real revolution in that sector by the arrival of centrifuges used at the beginning only for the separation Must-Oil and then even in the phase paste/Must. Nowadays, even though the evolution continues, we use basically two systems: the traditional one with super-presses and filtering disks and the continuous one with the centrifuges.
- Separation: once the separation of Oil from vegetation water occurred by skimming process; that is a special spoon (italian = "lecca" or "sfioro") by which you would fish on the surface of the must gathering basin as soon as the former let the oil physically lighter than water after resting for a while. Nowadays you vertical centrifuges are used (called separators) whatever is the extraction system; these latter give excellent results both regarding the separation speed and for high reliability of the engine. The principle is the classic one of separation by centrifuging process of a liquid made of element with different specific weight: as per a physical effect the heavier matters find place at the most external orbit proceeding to the central column as the matters are lighter. The Oil, that is the lightest substance among the components of the must, is contained along the internal pipe after passing by a series of cones that hold the impurities and sent by that to the gathering container.

- Conservation: through the centuries oil has aways been conserved in clay containers (amphoras, jars and pitchers), that only later were glazed: formerly by minium (lead powder) that melted during the cooking and fixed permanently to clay, latterly by suitable alimentary paints according to referring laws. Nowadays stainless steel containers are used in addition to these latter and more and more often replacing them. Whatever is the container it must have hidoneous requirements for conserving oil: you have to clean it easily with hot water and suitable grease-removers, it absolutely does not have to maintain bad smells, it does not have to let light passing through, it must have a cover to isolate the product from the air as much as possible (floating type), and must have an inclined bottom with a suitable end valve to eject solid tailings that sediment with the passing of time. The cleaning is the first requirement for conserving any food product; if that is the oil the most scrupolous hygiene is necessary. Oil can absorb smells existing in the environment in which it is preserved, thus you need to pay attention to eventual mouldy, rancid smells and to fuel ones (petrol, diesel and similar ones), that could be immediately absorbed by the product. Thus, as to resume, the oil must be preserved in suitable containers (stainless steel, other glazed ones etc.), carefully washed by sodium hydroxide or similar, in environments deprived from any smell, protected from even indirect light, at a temperature between 14° C and 18° C. Eventually, for a good preservation, the oil, (if not filtered) should be "changed", that means removed from its sediments as these fall down on the bottom of the container and possibly always held cleaned. You should better keep in mind that a limpid oil in relation to a veiled one is subjected to a higher oxidation risk.