The cultivation of olives involves constant attention to the quality of the olives themselves. In fact, the action of pathogens or possible weather events can damage the olives leading to degradations of internal compounds, such as phenolic and aromatic compounds. These degradations will reach the oil, increasing its acidity or creating substances that are unpleasant to taste and unhealthy.

The main damage, as we know, is caused by the olive fly, Bactrocera oleae, which pierces the drupe during stone hardening and deposits at least one egg inside the fruit. This develops into the larva that will tunnel inside the drupe to emerge as the fly. Even drupes in which eggs are not present may be subject to quality declines if only the fly has created a wound where it has not deposited eggs, in fact fungus, bacteria and other pathogens may develop from this and degrade the internal compounds of the pulp.

So to obtain quality oils it is very important to monitor your olive grove and minimize pathogen damage.

But that is not all that is needed, in fact, once the olives have been harvested some key steps must be taken for the oil to be successful in quality.

Post-harvest storage, preservation and transportation

During harvest, olives are stored inside crates, made of wood or plastic, 20-30 cm high with windows on all sides. Such features of the crates are essential to keep the olives in good condition, avoiding crushing, unwelcome fermentation, and increased moisture. The crates can also be placed on top of each other for transport.

Transport is done either directly in the crates or in crates of up to 4 quintals, always well ventilated; the latter is convenient for large farms since they can also be used in subsequent operations.

The maximum time for storage in the crates is 2-3 days to avoid oxidative and fermentation processes; the optimum would be delivery to the mill within 24 hours and milling within 48 hours.

Once arrived at the mill, long stops before milling and mixing with batches of qualitatively poor olives should be avoided. In fact, once arrived at the mill they still pass an initial quality control were damaged or poor quality olives will be removed.

Washing and milling of olives

Once at the mill and before continuing with the milling process, the olives will have to be aired to remove vegetable portions such as leaves and twigs as well as dust and stones. This will be followed by washing where they will be definitively cleaned of impurities and then passing over vibrating screens to remove water and the last foreign residues.

Following the washing the olives pass to the crushing stage, this stage allows to obtain a coarse paste thanks to the crushing of the whole olives (skin, pulp, and stone). The stone helps with drainage and the separation of the oil from the paste.

There are two crushing methods: the traditional discontinuous cycle, with granite grindstones crushing the olives, and modern continuous cycle, with a hammer or rotating disc crushers. Obviously, the latter result in higher quality oils due to the speed of processing, less oxygen within the cycle, and a more homogeneous paste.

Gramoling, extraction, and filtering

Gramolatura allows the mixing of the olive paste inside a machine called, precisely, gramola.

This phase is essential to form the actual oil, in fact, gramolatura lasts about 30 minutes with maximum temperatures of 29 °C to preserve the organoleptic characteristics of the oil. At this stage, the oil-water bonds are broken and allow the oil to come together in a single, more homogeneous liquid that will simplify extraction. The crucibles are made of watertight stainless steel that allow oxygen control.

Extraction, on the other hand, is the final stage of oil processing.

It is performed on circular panels that allow the oil to filter out of the paste itself through holes called fiscoli. For proper extraction, these panels are interspersed with steel discs for even pressure, stacked on special trolleys and placed under a press. For about an hour, increasing pressure is exerted, allowing the separation of the oily must (oil and vegetation water) and pomace (solid part).

Unfiltered oil will thus be obtained. To obtain the marketable filtered extra virgin olive oil, the oily must will be filtered so as to obtain the final product, a clean oil, and free of physical and sensory anomalies.