5 Olive Oil Curiosities  

Why is it called Extra Virgin olive oil?

The main olive oil production is exclusively based on mechanical extraction processes. In this way we can make a distinction between virgin oils and those obtained by processes based on physical and chemical methods (seed oils, adjusted and refined olive oils, olive-pomace oil). There are two extraction techniques: the classic and the modern one.

Other techniques involve the use of physical and chemical methods. It should be said that rules and quality standards prescribe that an olive oil can be defined virgin only if for its production exclusively mechanical methods have been used. The oil obtained with the use of chemical and physico-chemical methods is thus identified with different product categories which differ from virgin oil category.

The mechanical extraction production lines differ in the methods used at each stage, therefore, there are different types of olive oil mill plant. In addition to the technical characteristics, the systems differ markedly for working capacity, mechanization level, work organization, qualitative and quantitative yield, production costs. In general, the production line of an oil mill has five key stages:

  • preliminary operations;
  • milling;
  • oil juice extraction;
  • oil-water separation;
  • storage, clarification and bottling.

Generally speaking the yield of the olives may have considerable variation, from a minimum of about 8-9 kg of extra virgin olive oil per 100 kg of pressed olives up to a maximum of 22-28 kg of extra virgin olive oil per 100 kg of olives. Variations are due to several factors: the sun exposure of the olive trees, water availability during the olive growth and development season, the harvesting period.

When are olives harvested?

Olives are traditionally harvested (from mid-October to late December in Italy) on suitable nets, in some regions by beating the branches with flexible sticks, so as to cause separation of the fruits or waiting for the full maturation and consequently after their natural fall from the tree, in other regions. A more modern technique involves the use of mechanical harvesters that shake the branches, but with greater damage for the plant, and causing the fall of the olives on a prepared ground net that allows to pick them  faster and with less effort.

Olive hand-picking with special combs and shoulder bags (a labour intensive method, but that allows to select fruits) on long staircase with wooden pegs is still practiced in many parts of Italy. This technique is certainly the most expensive, but still allows to pick intact fruits at the right degree of ripeness. It is still preferable for preserved olives but it is the first of key elements to obtain an extra virgin olive oil, in short an EVOO, fragrant and free from any unpleasant smell.

There are fully mechanized harvesting methods using shaking machines with olive umbrella interceptor. Nowadays in olive tree groves specifically grown for the purpose (superintensive olive tree groves), the olive harvest is even possible by means of shaking machines suitable for mechanical harvesting of grapes (grape harvesters).

In order to obtain a virgin olive oil free from defects the method for olive storage is essential, too. It is of key importance that the olives are collected in special aerated plastic boxes (neither wooden boxes nor bags should be used) and that these boxes are kept away from heat sources and that the olives are pressed within 24-48 hours from harvesting. Such a storage method ensures that the olives do not ferment anaerobically giving rise to the formation of aliphatic alcohols which would produce in the oil defects such as heating and, in extreme cases, mold.

What is olive pomace?

The olive pomace is what remains after the extraction, and it is possible to extract more residue oil from it. In fact, pomace, according to the type of crusher, still contains from 3% to 6% of oil.

The pomace coming from traditional mills (equipped with presses) contains approximately 6% of oil whereas pomace from modern mills, the so-called continuous mills, contains about 3%.

This oil is extracted through an industrial process, precisely at factories specialising in the treatment of oil pomace by means of chemical solvents.

This oil, called crude pomace oil is not edible: through a refining treatment we obtain the refined olive pomace oil, which still is not edible; only after the addition of an unspecified percentage of virgin olive oil it becomes edible and is called olive-pomace oil.

This product is the only olive oil resulting from a solvent extraction process and is therefore the only oil resulting from olives that can be compared to a large part of seed oils available on the market.

Indeed most of the seed oils on the market are extracted using the same process. However, olive pomace oil keeps unchanged the fatty acid composition compared to olive oil, that is, with a high content of MUFA (mono unsatured fatty acid) with a percentage of 60-85%.

Why the olive tree is not a tree?

The olive tree is not a tree, is a shrub. But only in the Mediterranean area it has been acclimated giving it the shape of a tree.  It is thought to be typical of the Mediterranean, which is the emblem, but more than 40 species exist worldwide, as far as southern Africa and Oceania.

The name olive derives from the Cretan Greek where the letter “e” was represented by a stylized olive and fruit tree was called elaion, and in Latin “Olea”.

The special feature of this shrub is that it grows on the sunny side and rots on the shady one; man removes the rotten wood. In this way, the olive trees “walk” and new plants, which are always the same, but autonomous, move away from each other. A bi-millennium olive tree, then, is a plant that has changed at least fifty times its roots and from 2 to 3 times  its trunk. Yet it is always the same plant!

What is the maximal acidity, beyond which the oil is virgin?

The oil obtained from the pressing of good quality olives is called extra virgin, as it has undergone only mechanical and physical processes, ie pressing and extraction or squeezing, and must have a maximum acidity of 0.8, beyond which is classified as virgin, semi-fine or lampante olive oil; the latter is not edible. However, it is almost impossible to find on sale oils not classified as extra virgin olive oils.

Olive oils that are commonly on sale, labelled as “Olive Oil” are obtained from the chemical refining of lampante and virgin oils with a small addition of extra virgin oils. This process is achieved with deodorization and discoloration by means of chemical solvents. The same process applies to olive pomace oil, obtained using chemical solvents, too.