The life of a good extra virgin olive oil is punctuated by extremely precise time intervals and methods (harvesting, processing, storage, service and consumption). It is useful to be aware of the good practices governing these procedures in order to appreciate the oil and draw attention to its real value.
While allowing for the fact that each area has its own cultivation traditions which entail different pruning techniques (globe, inverted cone etc.) and that, in any case, the olive tree does not thrive in soil that is too damp or fertile, but prefers stony ground with rocky outcrops, the most important factor to ascertain when visiting an olive grove is that it has not been subjected to chemical weeding, with consequent destruction of the vegetation at ground level. Although such clean soil undoubtedly facilitates work, pollution of the trees is unavoidable.
The rule for harvesting is that the olives should be picked directly from the tree (never from the ground), that the olives should be healthy but not completely ripe (coloring) and that only boxes containing holes and a capacity of not more than 25 kg should be used (never sacks or bins).
During transport the utmost care and attention must be paid to ensure that the fruit is kept intact; it must be conveyed to the mill extremely quickly and milling must take place within 24 hours of harvesting.
ITALIAN EXTRA VIRGIN OLIVE OIL PRODUCTION CHAIN
These procedures are not the fruit of recent research but were already clearly described in ancient writings (Pliny, Cato, Columella) and provide confirmation of the absolute value of the natural oil production chain.
This applies even more strictly to the processing phase, which simply involves extracting the oil already present in the fibers of the pulp (vacuoles), freeing it from the solid residues and from the water.
Here, it is important to remember that we are, in fact, speaking of the only oil extracted from the pulp, and not from seeds, of the fruit, and the law has recognized this value, decreeing that a caption be placed on extra-virgin olive oil containers clearly stating: “superior category olive oil obtained directly from olives and solely by mechanical means ”.
After defoliation and washing, the harvested olives are sent to be milled, an action which reduces them to a paste which may be more or less coarse or homogenized.
MILLS, PASTE, EXTRACTION OF OLIVE OIL
The traditional use of the typical granite millstone is still a valid method if well conducted, although it is gradually giving way to mechanical mills (disc- or hammer-operated), which are easier to manage and regulate.
The olive paste is then placed in horizontal cylindrical malaxation containers (‘gramolatrice’) that have a mechanical arm inside that remixes the paste slowly until it has reached the most congenial conditions for releasing the oil and improving the yield, but this process must be carried out with the greatest of care in order to prevent the temperature from rising above 27°C, leading to dangerous oxidation phenomena. Of course, in the best mills today, these containers are equipped with thermometers, connected to a control panel that measures the levels reached, thereby guaranteeing optimal processing.
The next step, which is of fundamental importance, is extraction, i.e. the separation of the oil from the vegetable water and mass of olive residue (‘sansa’), after which it will be sent on for industrial refining.
The antique pressing method has, by this stage, revealed both its advantages (varietal imprint, phenolic richness) and its limitations (risk of fermentation and oxidation, long processing times, high costs, loss of aromatic freshness). The paste is poured onto discs with holes in the centre (‘fiscolo’), made of synthetic fiber (nowadays hardly ever of natural fiber), creating a layer a few centimeters thick. These are progressively stacked on a steel pole with holes, secured to a wheeled base. One steel disc with holes is placed for every 5 fiber discs (usually to improve stability and extraction), then the ‘tower’ is placed in the pneumatic press where it is subjected to progressive crushing, for approx. 30 minutes. These conditions generate the expulsion of an oily must which pours into the collecting tank underneath and from there to the centrifuge for the final separation of the extra virgin oil from the watery part.
The solid parts remain trapped in the fiber discs and when the ‘tower’ is disassembled, they will be cleaned of the oily residue and a new load will be prepared for pressing.
In order to achieve separation by centrifugation, the malaxated paste is first rendered more fluid by adding water, after which it is conveyed to the decanter, i.e. to a large horizontal centrifuge. The water must not exceed 27°C in order to enhance the components of the oil, while balancing the yield, and in order to be entitled to use the definition ‘cold extraction’. Recent applied academic research has, however, revealed that no significant deterioration processes are triggered up to 31°C, while from 40°C upwards, the maximum yield is obtained but with an immediate and inevitable deterioration in the quality of the product.
The decanter expels, separately: vegetable water, which is collected and conveyed to water purification plants and subsequently used for irrigation; oil residues, which are sent to processing and disposal facilities; oil. The latter proceeds to the final processing phase in the vertical centrifuge which separates and expels any residue still remaining from the oil.
Modern production of EVOO
The modern ‘continuous cycle’ production method, which is the most widely used today as well as being mandatory for certification as oil from organic farming, means that the entire operation can be carried out without interruption, from mechanical milling to separation by centrifugation, with obvious advantages, including rapid processing and maximum cleanliness.
Also the delicate oil storage phase is subject to a number of fundamental regulations designed to protect it from the risks connected with it being a fat, i.e. oxidation or the absorbing of unpleasant (or otherwise) odors, such as might be produced by exposure to light and temperatures.
Oil does not improve over time but can maintain its characteristics excellently if stored in glass or stainless steel containers, that are always clean, dark or protected from direct sunlight and kept in a cool place at a stable temperature (12-15°C) free from any type of odor (chemicals, fuels) or penetrating smells (onions, mould). If oil with a cloudy appearance is not bottled quickly, it will have to be periodically decanted (at least once every 4 months), to prevent it from absorbing the fermentative smell of the sediment. If low temperatures cause the oil to ‘freeze’, its antioxidant powers will be irrevocably compromised and its shelf-life shortened. Among state-of-the-art producers, there is an ever increasing tendency to use stainless steel, temperature-controlled vats (similar to wine vats), saturated with nitrogen, in order to preserve the extra virgin olive oil from oxidation and be able to offer a product that is always fragrant, with all its organoleptic qualities intact.
text edited by Stefano Asaro