Italian olive oil
The olive tree is one of the most typical characteristics of the Mediterranean environment, and olive oil is one of the oldest and most important products of the material culture in this part of the world.
The history of the cultivated olive tree begins during the fourth millennium BC. Its spread is linked to the development of the great Mediterranean civilizations, from the first organization of states in the Middle East to the contemporary world.
During the Middle Ages olive oil became very rare and valuable, so much so as to be sometimes considered cash. In fact, starting in the 5th century, state control over olive oil started to decrease, until it almost disappeared. Religious orders owned the greatest share of the olive trees still cultivated, and oil could only be found at the tables of rich people, but, above all, churchmen.
In monasteries the food supply attendants, in charge of the stores, gave oil to everyone each day to season their food, with neither extravagance nor avarice.
Olive cultivation and oil production can be performed only within a stable society, with a rather advanced and complex political and economic organization. In fact a rather sophisticated knowledge of botany and agricultural procedures (pruning, grafting), as well as the development of specialized techniques are required. For this reason the spread of cultivated olive trees has met with changing fortunes throughout the millennia, subject to social, economic and political conditions.
Olive oil is a fruit oil obtained from the olive (Olea europaea), a traditional tree crop of the Mediterranean Basin. It is used in cooking, cosmetics, pharmaceuticals, and soaps. Olive oil is considered a healthy oil because of its high content of monounsaturated fat (mainly oleic acid) and polyphenols.
Over 750 million olive trees are cultivated worldwide, with about 95 percent in the Mediterranean region. About three-quarters of global olive oil production comes from European Union member states; of the European production, 77 percent comes from Spain, Italy, and Greece.
The Italian government regulates the use of different protected designation of origin labels for olive oils in accordance with EU law. Oliéra has the Denominazione di Origine Protetta (DOP) Olive oils from the following regions: Riviera Ligure, Umbria, Terra di Bari, Toscano, Valli Trapanesi and Colline di Romagna.
Among the many different olive varieties used in Italy are Frantoio, Leccino Pendolino, and Moraiolo.
The most traditional way of making olive oil is by grinding olives. First the olives are ground into an olive paste using large millstones. The olive paste generally stays under the stones for 30 � 40 minutes. After grinding, the olive paste is spread on fibre disks, which are stacked on top of each other, then placed into the press. Pressure is then applied onto the disk to further separate the oil from the paste.
Production Techniques
The oil contained in olives is extracted by a multi-stage process: crushing, kneading the resulting paste, collection of the free flow oil, pressure separation and collection of residual oil in the grinds, separation of solids and vegetation water from the olive oil. The finished oil is then carefully stored to assure conservation of its sensory characteristics.
Crushing
The oil in olives is contained in special cells mainly in the pulp and pit. In the first stage of processing they are crushed to release the oil. During this phase, the oil and the water contained in the olives (50%) emulsify. The prolonged mixing of the paste, at a constant temperature, breaks down the emulsion and causes the minute drops of oil to combine into a large mass which will be more easily separated in subsequent phases. This operation is called kneading.
Traditional millstones are still used in some olive mills, but generally they have been replaced by mechanical crushers. The latter consist of steel cylinders enclosed in a metal housing. The olives are fed between the cylinders that turn against each other at a speed of more than 1,800 revolutions per minute and crush them to a thick paste. Cooling water flowing in a jacket surrounding the cylinder housing maintains the paste at an optimal temperature for extraction of the oil. Excessive heat can compromise the quality of the oil. Some very modern mills manage to reconcile requirements of modern processing with the advantages of older methods. In these mills, olives are crushed between two cylinders made from Norwegian granite, a rock that has a particular texture with carefully arranged grooves running along its surface. Crushing is carried out without altering the characteristics of the oil. The kneading is done inside steel basins where the paste is mixed for long periods by special blades fixed on a worm gear.
Extraction
The olive paste contains a percentage of oil varying from 18% to 27%, which can be extracted with different methods. The yield, that is to say the quantity in weight of oil that can be extracted from 100 kg of olives, depends on the type of olives, on the amount of water received by the plant, on the fertilizing, on the harvesting system, and above all on the extraction technique.
The most recent techniques have radically changed the oil extraction concepts and methods. In modern olive mills extraction from the olive paste is based on the principles of centrifugation and a process called "percolation" (not to be confused with the coffee brewing process).
Centrifugation: This process exploits the specific weight differences between water and oil. The water-thinned paste is churned at very high speed in a horizontal centrifuge. This results in the separation of the three components of the paste: oil, vegetation water and the pit and pulp residue (pomace).
Percolation: This method of separation is based on the different surface tensions of oil and water. We can understand how it works by dipping a metal blade, such as a table knife, into a glass of oil and water. When we pull out the blade we will note that only the oil has adhered to it. Thus percolating machines have been designed to dip numerous steel blades, attached to a continuously moving belt, into a receptacle containing the water-thinned olive paste. As the blades move out of the water their load of oil drips off into a collecting basin. This technique allows the extraction of about 50%-70% of the oil in the solution and results in an excellent product, free of any contaminants. The oil not picked-up by the percolation process is then recovered from the remaining oil and water solution by centrifugation.
Stainless steel tanks are the modern standard for the storage of large quantities of olive oil; they afford protection from light and easily sanitized, thus offering highest guarantee of correct conservation. Proper conservation of olive oil in the home is likewise important: it must follow the criteria of safeguard and protection that the characteristics of the product require. If correctly stored, olive oil can be consumed even mere than two years after it was produced because it contains antioxidants that protect it from becoming rancid. The containers must be of dark glass or tinplate, to protect the contents from light, and must be stored in a dark, cool place.
Clarification
The oil extracted from the paste still contains emulsified water, fruit particles and mucilage in suspension. These substances compromise the quality of the oil as much as they promote oxidation, hydrolysis and fermentation. They are removed by processes of clarification.
Even oil obtained with modern extraction systems, regardless of the one adopted, is still a crude must, turbid and opalescent due to impurities. Generally it is left to decant until the latter have settled. The oil is then channelled to other containers. The most demanding producers filter the newly extracted oil with special cellulose filters that are capable of blocking the tiniest impurities and even microscopic drops of water.
Storage
Perfect storage conditions are essential for the protection of olive oil from its worse enemies: light, heat and air oxygen, that can cause irreparable damage to the chemical and sensory characteristics of even the finest extra virgin oil.
Stainless steel tanks are the modern standard for the storage of large quantities of olive oil; they afford protection from light and easily sanitized, thus offering highest guarantee of correct conservation. Proper conservation of olive oil in the home is likewise important: it must follow the criteria of safeguard and protection that the characteristics of the product require. If correctly stored, olive oil can be consumed even mere than two years after it was produced because it contains antioxidants that protect it from becoming rancid. The containers must be of dark glass or tinplate, to protect the contents from light, and must be stored in a dark, cool place.