Museo del Olio - Trevi, It

The legendary Museum of Olive Oil Culture in Trevia, Umbria.  Notice the emphasis on the five "S"...

The following pages are taken directly from the famous Olive Oil Museum in Trevi, Italy, during my visit to an olive oil festival in the City Center, with many local restaurants participating in the two-day event.   It is quite an in depth look into our beloved olive.


The olive tree, in botany called Olea europaea, belonging to the order of the ligustrales of the Oleaceae family, is the only among the various species of the Euelae branch that produces edible fruit called drupes.  In the botanical classification there are two groups of trees: wild olive trees (oleaster or silvestris), characterized by intertwined branches with small leaves and fruit, and cultivated olive trees (sativa o communis) with lancolate leaves and fruit of various sizes.  The latter variety grows in sandy or arenaceous terrains but prefers loose terrains or of medium consistency, fresh and well drained, of a calcareous nature and also in areas that are very steep.  It develops in temperate climates; air that is hot or soil that is too wet or too dry limits its productivity.  It cannot bear low temperatures, it also suffers if the temperature drops anywhere below zero, also causing a loss of vigor in the arboreal species.

   It is a plant with a very long lifespan that can live as many as a thousand years thanks to its capacity to regenerate itself from the stump through the pollens that grow directly from its roots.

   In the Mediterranean area there exist more than 1000 genetic types of olive trees.  In Italy there are approximately 500 cultivars of which the most widespread are the Coratina of Puglia, the Frantoio of Tuscany, the Rosciola of Lazio and the Taggiasca of Lavagnina of Liguria.

   The location of the olive groves along ideal climactic bands, on arid and permeable foothills, is the condition that favors a slow maturing of the fruit of the varieties typical of central Italy: Dolce Agogia (Trasimeno). San Felice (Giano of Umbria, Gualdo Catteneo, Montefalco), Frantoio, Leccino, Maurino, Moraiolo, Pendolino (Regional), Nostrale of Rigali (Gualdo, Tadino), Rajo (Colle Amerini).  This slow maturation process gives the Umbrian oil its heterogeneous characteristics that are found in the various Umbrian DOPs – Colli Assisi-Spoleto. Colli Martani, Colli Amerini, Colli del Trasimeno, Colli Orvietani.

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The Trevi landscape is characterized by a dominant cultivation of olive trees.  It is the result of much care, attention, and hard work, which have made it possible to make an apparently inaccessible area bear fruit.

   This area is referred to as the piedmont (foothill) strip, that is, the area between 300 and 600 meters above sea level.  It gets its name from the fact that it is generally the zone that acts as a juncture between the flatland and the mountains.  Here the terrain is composed of soil that is not very deep, that rests for the most part upon the so-called “scoglio”, that is, rock derived from the disintegration of calcareous rocks that fall into the valley following crioclastic phenomena (disintegration of the rocks after repeated phenomena of freezing and thawing).

   These characteristics allow for the development of the olive tree.  In fact, this type of terrain is quite permeable. Allowing the water to flow rapidly towards the valley, preventing the humidity from being held for too long; furthermore, the altitude prevents the plant from being attacked by dangerous parasites (such as the fly, for example, which lays its eggs in the flower and ruins the fruit).

   On the other hand the piedmont strip presents certain limits that are of significant importance: first of all, the land is often very steep, at the limits of what is practical, furthermore, and worse still, the low temperatures reached during certain periods during the year periodically cause the phenomenon of “frost”.

   As far as the slope of the terrain is concerned, the problem was resolved during the course of the centuries, adapting the steep slopes to man’s needs, creating artificial shelves like large ledges, terracing and lunettes (small terraces marked off by small stone walls in the form of a semicircle inside which the olive tree was planted).

   Frost, instead, remains a practically invincible enemy.  It is synonymous in these parts with the worst misfortune, as it dries out the plant and leaves no other choice but to cut it down, leaving only the roots so that they may then germinate again.  It is not by chance that the olive trees in these areas never get very big, in contrast to those in other areas, precisely because the frost arrives periodically forcing them to start again from scratch.           

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Pruning is the process in which the trees are trimmed of excess branches in order to improve their productivity and facilitate the work on the plant. 

   Considered since ancient times to be a true and genuine art, pruning holds an important place among the many devices and treatments necessary for obtaining a satisfying product from both the qualitative and quantitative points of view.

   The regular and productive growth of an olive plant, in fact, is the result of a subtle balance of many factors: it would be useless to irrigate or fertilize a tree if an excessive number of branches or their poor positioning prevented the exposure of its leaves to the sunlight or proper oxygenation.  The leaves are the biochemical laboratory of the olive tree, and from them, thanks to the process of photosynthesis, the tree receives part of the nourishment it needs for germination and subsequent fruit bearing.

   A good pruning, furthermore, facilitates the process of harvesting the olives as it renders the fruit more reachable, thus optimizing the harvesting process, which in the area of Trevi is still carried out predominantly by hand, thus reducing the labor costs.

   In the end, it is best to “build” a tree with expansive foliage that receives sunlight everywhere and has the largest quantity of fruit bearing foliage close to the ground.

   There are two basic types of pruning:

            -One is for forming the young plant, intended to give the plant a regular and rational form for its growth;

            -For productivity, meant to maintain a regular arboreal skeleton, to renew and favor the productive branches and to shape the plant so that all the leaves have homogeneous oxygenation and exposure to sunlight.

   These are the general guidelines. However, as with every art form their application is very subjective and therefore when the time comes to harvest the olives, disagreements, at times quite heated, inevitably arise among the senior harvesters regarding the best or the worst method of pruning of the one or the other.

   The olive tree should be constantly cleaned in order to never prune it, since the able pruner is not the one who knows how to cut, but rather one who knows when to trim the plant in such a way as to maintain the tree clear of branches that have grown incorrectly, or are weak or almost dry; and in thinning it in such a way that every part receives abundant exposure to the sun and air, both the inner branches as well as those on the outside, to the point that there is not even one branch which during the course of the day does not reap the benefits of the sun.                   

   The Trevano is such a lover of cutting large branches that rather than maintaining those branches that he believes are old, he rejuvenates the plant with secondary shoots, the majority of which should be removed. The olive trees of Montefalco are split, truncated, bare and have very few fruit bearing branches.  Those of Giano are prosperous, vigorous, full of foliage and very beautiful also to the eye.

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The harvest is the crucial moment of the productive chain that spans from the plant to the finished product. First of all, it is necessary to choose the phase of the fruit’s maturation that is most suited to the type of product you want to obtain.  An early harvest, in fact, along with a lower yield, that is, of a lesser quantity of oil obtained from each individual olive, will give the oil different organoleptic qualities and taste with respect to a later harvest.  During this stage, one should keep in mind different aspects, in particular the integrity of the fruit.  In fact, it is indispensable that the olive goes from the plant to the mill without bruises and basically in the best condition possible.  Furthermore, it is important that not too much time is allowed to pass between the harvest and the pressing.  All of this in order to obtain a product of the most excellent quality in terms of its chemical qualities and, above all, taste.  The harvest is a very delicate stage that if carried out with little skill could compromise the work of an entire season.

   In the Zone of Trevi the prevailing technique has remained basically unchanged.  It is called brucatura (cropping) or, if performed with small rakes, pettinatura (combing).  The work is very slow (each harvester can be expected to harvest between 80-90 Kg of olives per day) but the product obtained is of the highest quality, suitable for either the table or the mill.  Other traditional techniques include:

            -Raccattatura or spontaneous falling: used mainly in the regions of Southern Italy (Puglia) where the olives are left to fall to the ground after having laid sheets under the plants.  This way it’s enough to collect the fruit that falls there.  Though this method is economically advantageous, it yields an inferior product since it will mix in to the harvest some olives that are too ripe or rotten and others that are soiled with dirt.

            -Bacchiatura (knocking down): the plants are beaten with poles, thus causing the olives to detach from the plant.  This method, though offering an excellent execution rate (each harvester can harvest between 5-6 plants per hour), presents the obvious disadvantage of significantly damaging the fruit and thus rendering it useless for table consumption.

   Naturally, in the course of time these manual methods were complemented by others making use of mechanical apparatus.  This is the case for example with the scrollatura (shaking) method; which consists of attaching a mechanical arm to the plant or to the individual fruit bearing branches which are then jolted, thus causing the fruit to detach.  It is a quick method, that guarantees practically absolute integrity of the olives and that, if used on a vast scale, allows for the further reduction in labor costs (one person can harvest up to 10 q of olive a day).  The drawback, however, is that the plant could be damaged as a result of the vibrations.

   During the olive season, precautions were often taken to prevent the olives from being stolen; special guards, domiciliary inspections of non landowners, the Mill owners were forbidden to accept olives that had been “knocked down” before the end of the season.

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The transformation of the fruit into oil takes place at the oil mill.  There are various extraction methods, among which two main ones:

            -Exclusively mechanical at low temperatures, the only one that by law qualifies the oil as “virgin” or “extra virgin” (base on the acidity level); it consists in crushing the olives in order to extract the pulp;

            -Mechanical and chemical, consists in adding a series of reagents that modify the acidity of the oil in order to make it conform to predefined parameters, used for about all vegetable oils, rectified oils or sansa oils.

   In both cases, independent of the type of milling used, the operation can be separated into five phases;

            Preliminary operations:

            The olives, brought to the olive mill on the same day they were harvested, are defoliated with the help of the stationary or vibrating screens to eliminate the leaves and larger twigs that otherwise could leave the oil with an acid-bitter or woody taste.  The olives are then washed to eliminate the fermented juices of the crushed olives.

            Pressing or Milling:

            The olives having been prepared for milling are dropped by gravity into the mill, where two millstones, rotating around an axis, crush the olives without increasing the temperature, forming a paste.  This procedure is meant to break down the fruit’s cellular walls and to grind the fragments of stones with the pulp to allow for the extraction of the pulp.

In the modern, highly automated oil mills, automated mills equipped with disks or hammers are widespread.  They consists of a series of rotating hammers that crush the fruit, obtaining the same effect as the millstone but in a much shorter time (a few seconds as opposed to the 20-40 minutes of the traditional method).

            Malaxation (Mixing):

            From the milling an initial quantity of oil is obtained, but the paste produced, consisting of pulp and crushed rock, still contains a significant quantity of oil.  In order to extract it, the paste is loaded in the mixer, a machine consisting of a long tub within which the paste is kept agitating slowly.  This movement facilitates the gathering of oil in drops that are large enough to allow for the subsequent separation from the water.


            There are a variety of technologies applied for separating the oil from the paste.  Among the most used is the discontinued press technology, also called the traditional method.  In this case the paste is placed on fiscoli (discs made with woven synthetic or plant fibers) and pressed with hydraulic presses to obtain a larger yield of oil.

            Separating the oil from the water:

            Once all the oil is extracted it must be separated completely from the water it naturally contains.  This process is usually performed using centrifuges, which with a rotation of 6000-7000 rotations per minute, taking advantage of the different densities of the two liquids, make it possible to obtain the product pure and edible, even if opaque due to the presence of debris of pulp and fats (slush). 

             Storage, clarification and bottling:

             At this point the product is poured into stainless steel drums and stored at a controlled and constant temperature, in contact with nitrogen to avoid oxidation, for a period of time that varies depending upon the maturation characteristics desired of the product (usually a few months).  This process also serves to decant the last impurities and obtain transparent oil that is ready to be bottled and introduced on the market.