Olive oil is the substance extracted by crushing olives, it is the typical ingredient of the Mediterranean cooking, and it is also used to preserve foods, in the past it was also used as a combustible for lamps.

 Olives, from which the oil is extracted, are the fruits of the olive tree (Olea Europea), an evergreen plant, very longeval and that belongs to the family of Olea species. Flowers, after having been fecundated, generate fruits having a pulp rich in fatty substances: the olive. Olive tree is a plant having very ancient origins and it spontaneously grows in the entire Mediterranean area, however, nowadays we can consider this plant as cultivated just because man, since a very long time, has improved its cultivation techniques in order to get a rich and abundant harvest of fruits. The olive tree is more demanding in terms of climate than of soil, it has its ideal environment in the Mediterranean countries where summers are hot and dry and winters are rainy. The main purpose of the cultivation of the olive tree is the harvesting of fruits to be used in the production of olive oil, a condiment broadly used by the people of the Mediterranean which prefer this condiment to animal's fat, mainly used by the people of the northern areas of Europe.

Olive Trees

 Olive tree, its fruits and the oil produced with them, are part of the culture of man since the beginning of the history of humanity. It is supposed that the olive tree was cultivated in the Middle East since 8000 years ago. The first cultivations were probably done in Syria, Crete and Palestine where the most ancient oil presses were also found. Appreciated by Babylonians and Egyptians, the spreading of this wonderful tree in all the Mediterranean area was done by Phoenicians. Greeks were assiduous cultivators of olive trees, however were Romans that spread this tradition in all the empire. Sometimes, the tax revenue service of Romans wanted taxes to be paid in olive oil. The Romans were also the first ones to build the very first tools for olive crushing as well as improving the techniques for the storage of olive oil.

 Olive tree is frequently cited in the Bible, in the Koran and in classical text of the Greek and Roman culture. In the course of some archaeological excavations conducted in the Mediterranean area, many tools for harvesting and crushing olives were found. Since ancient times, this plant has had a very important role: with olive man wanted to symbolize peace and the prosperity of people. The olive is a symbol of longevity, knowledge and beauty, it was used by Romans to ornate the head of the winners of games. It was also used in religious ceremonies.

 Even now, olive has not lose its relevant importance, olive oil has a prominent role in the well known and renowned “Mediterranean diet”, many experts agree on its many beneficial qualities for our health.

 Olives mature in a very gradual way and this allows to organize the harvest in order to send olives at the oil press facility as soon as olives are harvested and to prevent their alteration. For more than 2000 years, the harvest of olives has practically not changed, they are usually harvested by hand, in order to guarantee the best quality of oil because, by doing so, olives are not damaged and, last but not the least, the plant does not get damaged as well. This is almost impossible in case nets are being used or, even worse, when olives are harvested as they fall from the plant to the ground. Technology also offers mechanical tools for harvesting olives. These tools shake the tree in order to detach olives from the plant and fall down. There also are tools, very similar to “vibrant combs”, that when passed on the branches of the tree detach olives from the plant and fall down to a net and subsequently gathered.

 The time of harvest greatly influences the physical and chemical characteristics of oil. Olives which are not fully ripe will give a green colored oil, having fruity aromas and slightly bitter flavors, whereas full ripe olives will produce a product having aromas of ripe fruit, fundamentally sweet and with a higher level of acidity. To determine the best time for harvesting olives, the following factors are being considered: color of olives, softening of the pulp, the quantity of oily substances and the resistance to detachment.

 This first stage of process must not be underestimated because in case the olives stay for too much time in the branches, or are left in the ground for too long they could get damaged, and this would greatly compromise the production of a good oil. In order not to compromise the quality of olives, the best thing is to send olives to the oil press facility within 48 hours from the harvest. This incredible fruit is so delicate that a proper attention has to be paid even to the kind of container used to keep them. A plastic container having holes on every side, including bottom, will ensure a proper circulation of air and avoid fermentative and oxidative processes of the fruits. Sacks are to avoided anyway because olives would get crushed and this would start those processes that would irremediably damage them. Another container that should be avoided is a wood containers because it could be easily affected by molds.

 As the olives are gathered they are promptly shipped to the oil press facility where they are selected, separated from any possible leaves or extraneous elements, washed, ready to go through the first stage of the process, the crushing process. The crushing breaks the oily cells contained in the fruit. In the past, when presses had a lower efficiency of those used nowadays, after having preliminarily crushed, hot water was added to the crushed paste in order to continue the crushing process and therefore to extract more oil with subsequent crushing phases; only the very first crushing could be legally called as “primary cold crush”. Nowadays all of the oil produced is extracted in a single crush and only the residual, called “husk”, is subsequently refined.

 There are currently two crushing methods for olives. There are high velocity stone wheeled crushers and metal wheeled crushers. According to the type of crusher as well as the method used for crushing olives, depends the following stage: pressing. Alternatively, the crushing of olives can also be accomplished by using other types of crushers such as those having hammers, disks, cones or rollers. The usage of a proper crusher also ensures a good extractive yield. The strength at which the olives are being crushed influences the aroma and flavors of oil. As the olives are transformed into a paste, it is processed by a kneading-machine. During this phase, the tiny drops of oil get in contact one each other and form bigger and bigger drops that can be finally gathered. This phase is connected to the preceding one because the quality of the final product depends on the type and the temperature of the paste, as well as the quantity of time spent on the kneading-machine. This method of extraction is called “classic” or “discontinued” because it requires pauses during the process in order to allow the paste to be spread on filtering diaphragms and therefore forming the so called “pressing tower” which is subsequently processed by a pressure of 400-600 atmospheres. (5.6-8.5 ksi) This method of processing is sometimes replaced by the centrifugation process because it needs a continuous maintenance of the filters which are severely altered by the high pressures with the subsequent risk of passing some unwanted substances or aromas to the oil. The kneading process used in the “classic” method usually takes place at room temperature. (20-24° C - 68-75° F)

 The centrifugation method, also known as “continuous process”, as it does not need any pause between the phases, is become very common nowadays. The olive paste is being processed by a centrifuging machine at 3500 rounds per minute, which produces an emulsified oil and a subsequent increase of the velocity ensures the water to be separated from the oil. In this case the working temperature is slightly higher, however it should never be higher than 30° C (86° F) in order not to favor peroxiding and therefore damaging the oil's organoleptic qualities as well as the preservability of the product itself. The residual, called “husk”, goes through a different kind of process and it is refined in order to be used for the production of other things.

 It should be said that olive oil lovers know very well that, just like for wine, the taste is greatly influenced by natural factors such as sun, climate and quality of harvest, it can have fruity aromas and flavors, spicy, sweet, bitter as well as having other organoleptic qualities. By pressing olives it is produced the so called “olio vergine” (Italian for “virgin oil”) also known as “prima spremitura” (Italian for “first pressing”), viscous and having a green-yellow color, rich in fatty substances. Subsequent pressings give oils of lesser value. Residuals of this process, called “husks”, still contain a quantity of oil of about 5 to 10% and that be extracted by means of pressing. Production technologies, physical and chemical characteristics, organoleptic qualities, as well as the quantity of acids, all determine the category to which an olive oil belongs to.

 The categories of olive oil, according from the many processing methods, are:

• Extra-virgin olive oil - It is the best olive oil. It is virgin oil, not processed by any refinement or filtering technique, and its acidity (oleic acid) cannot be higher than 1%, that is not higher than 1 gram for every 100 grams. (0.03oz per 3.5oz) Its specific weight varies from 0.913 to 0.925, its point of solidification is from -2° C to 10° C (28.4° F to 50° F)
• Ordinary virgin olive oil - (also known as “pure”) It is the oil produced with mechanical systems and in thermal conditions that would not alter the product, they cannot be processed by any unconventional method except washing, centrifugation, filtering and decanting. The level of acidity is of about 2%
• Fine olive oil or olive oil - It is a refined olive oil to which is added some virgin olive oil in order to improve the taste. The maximum level of acidity is of about 1.5%
• Husk oil - It is composed by husk, that is the residual from the olives processing, refined with chemical solvents. When this oil is added to virgin olive oil it gives “husk olive oil”. The maximum level of acidity is of about 1.5%

 Besides virgin olive oil and extra virgin olive oil, there are other classifications, however these oils cannot to be used for direct consumption:

• Ordinary olive oil - It is an olive oil having a maximum level of acidity of about 3.3%. Added to refined olive oil gives “olive oil”
• Lampante olive oil - (“lampante” is an Italian term indicating something which is suited for lamps, in this case means an oil to be used as a combustible for lamps) It is an oil having some defects and more than 3.3% of acidity
• Rectified olive oil

 There also are other refined olive oils, obtained by the refinement of olive oils having a maximum level of acidity of 0.5%. Moreover, husk olive oil can be classified in the following categories: raw husk olive oil, refined or rectified husk olive oil and oil of olive's husk.

 It should be noticed that rectified oils are processed in a way that compromise the typical organoleptic qualities of olive oils; in the “olive oil” and ”husk olive oil” there is no indication about the minimum quantity of virgin olive oil or extra virgin olive oil that was added to the final product. The European Union, in order to safeguard the quality of olive oil as well as safeguarding the quality of other products and their area of production, has creates the DOP mark (Denominazione di Origine Protetta, Protected Denomination of Origin) which identifies the denomination of a product that was produced and processed in the geographical area designated and recognized by a committee. Another mark instituted by the European Union is IGP (Indicazione Geografica Protetta, Protected Geographical Indication), which identifies the origin of a certain product from a specific territory and requires that at least one of the production phases, or one of the transformation phases, was done in that specific geographical area.

 The determination of free acidity in an olive oil is an important factor that also determines the quality. As the acidity increases, a series of physical and chemical modification occur as well as the alteration of organoleptic qualities that would compromise the oil's quality. An oil having a low quantity of acid will be considered the best, it can be easily preserved and will have superior organoleptic qualities. Unfortunately, the level of free acidity is not always indicated in the label. It is best to trust the producers who write this value in the labels and it would be best to prefer oils having a value of acidity lower than 0.3%. Lastly, price should be considered as well, excessively low prices should be distrusted, and excessively high prices should be avoided as well, after all it is olive oil anyway.

 Each gram (0.03oz) of olive oil gives 9 Kcal, just like any other oil, and the belief that other oils have more calories than olive oil is therefore untrue. The quantity of fatty substances is the same for every oil (like to say, they make you get fat in the same way), however olive oil should be preferred because it is nutritionally superior, it is rich in anti-oxidants substances and vitamins as well as having good quantity of acids. The best way to store olive oil at home is to keep it from light, in a clean room and at a temperature from 12° C and 24° C. (53° F to 75° F) The so called “smoking point” of olive oil, that is the tolerance to high temperatures, is very high, also thanks to the many anti-oxidants substances the preserve its composition. In consequence of this, the common belief that olive oil is not suited for frying foods is not true.

 Olive oil is the only oil to be produced by the simple crushing of a fruit, without using any chemical substance, and it is mainly composed by monounsaturated fats and chlorophyll, lecithin, linoleic fatty acid, phenolic compounds, vitamin E, vitamin A, vitamin D and beta carotene. These anti-oxidants substances make olive oil very important for our health. It is scientifically proven that a constant consumption of olive oil favors the lowering of LDL cholesterol (the bad cholesterol) while favoring the increase of HDL cholesterol (the good cholesterol), as well as preventing vascular and heart diseases, particularly atherosclerosis, lowering the risk of arteries' blockage, as well as lowering stomach's acidity, blood pressure and the quantity of sugar in the blood. Extra virgin olive oil consumed in the morning, before having breakfast, seems to be a good remedy for constipation.

 Despite the fact the cultivation of olive tree is pretty common, consumption of olive oil is limited to the countries of the Mediterranean area, in other countries the most consumed oils are those of peanuts, colza-seeds, soybean and sunflower seeds. Olive oil is the best oil to be used for cooking and in particular to be consumed raw without any cooking process, however even when cooked it still remains one of the best oils for human nutrition. Other oils should be consumed, except for peanut oil, with some caution. Thanks to its proper characteristics and qualities, olive oil can be considered as one of the best oils.

 The best time of the day for tasting is the interval of time that precedes lunch, that is between 10:30AM and 12:00AM, because taste buds have not been altered by other factors yet and therefore are more sensitive and do their job better. Tasting temperature should preferably be of about 28° C. (82° F) Tasting olive oil consists in evaluating its color, its flavors and taste as well as its aromas. This can be easy to say but it certainly requires lot of experience and lot of practice in order to recognize and evaluate an olive oil. Moreover, it should be said that tasting techniques varies from taster to taster.

 First of all a small quantity of oil is being poured in a glass container, that is a container that does not alter the contents with its possible flavors or smells. After the oil has been swirled in order to evaluate its fluidity, the color as well as the nuances are being evaluated: a limpid or cloudy color in a non filtered oil or young oil are factor of good quality; whereas a turbid aspect or, even worse, a orange-reddish color, indicates that an oxidation process is taking place. Smell the oil sample in order to evaluate all its aromas and the bad smells. Take a small sip, the quantity of a spoon will be enough, and vigorously inhale air in order to vaporize part of the oil in the mouth, without swallowing, and in order to stimulate the taste buds at best, keep the oil in the mouth for at least 10-20 seconds. Take a little break and then inspire air again while keeping the lips almost sealed and the tongue on the upper palate. Repeat the inhaling and vaporization phases more times and therefore expel or swallow the oil. While moving the tongue on the palate, evaluate the final flavors.

 Aromas and flavors or mature fruit, particularly of apple, aromas of olive fruit, nuts, musk and undergrowth (in case this latter sensation is light it is considered to be typical for some areas), herbaceous, tomato leaf, artichoke, are all to be considered as positive factors; whereas bitter, pungent and sweet flavors, in case they are not excessively accentuated, can also be considered as acceptable and positive. Negative factors are sensations of sour, acid, metallic, mold, rancid and carbolic acid. Olive oil tend to absorb odors and smells of the room where it is being kept, therefore in case strange or funny smells that would resemble the ones of some environmental conditions are all to be considered as consequence of a bad storage.

 Lastly, the following list is a group of terms commonly used for the classification of the organoleptic qualities of olive oils.

• Sweet - it is said of an oil having gentle aromas and a final taste of almond without being excessively sweet or faint
• Bitter - is a negative factor because it reveals an oil produced with not fully ripe olives, bitter flavors can also be followed by flavors of leaves and wood. Only a slight flavor of bitterness can be considered as acceptable
• Pungent - is the typical flavor of young and fresh olive oil, the ones having a brilliant green color, and that tends to disappear with time
• Harmonic - it is an oil having no defects. Surely the best
• Aggressive - it is an oil having some components excessively intense and that cover all the other sensations
• Oxidized - it is an oil that was exposed to the air for a long time and that is going rancid. It is not edible
• Limp - it is said of an oil which is unctuous and lost its aromas
• Mature - an oil having fruity aromas, fundamentally sweet and having a golden color
• Exhausted - it is an oil which is getting old