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Characteristics-Composition of olive oil... It is well known that the characteristics of an olive oil depend on many factors: cultivar, pedoclimatic conditions, method of cultivation, era and olive picking system, transformation technology and method, and product conservation. Olive oils differ both for their organoleptic characteristics (aroma, smell, taste) and for their chemical properties (composition, acidity, etc.). Many of the factors that influence the quality of an oil cannot be modified (e.g. pedoclimatic conditions), as they are characteristic of a given location. Others, however, can be easily adapted, such as the growing techniques and means of extraction. Thus, in order to produce an excellent oil, one must identify and highlight its best organoleptic and chemical characteristics which are worthy of attention by the consumer. Olive oil is a fat that is presented in liquid form at room temperature (20°C). From a chemical point of view it consists of 98-99% triglycerides, or a so-called “saponifiable” fraction. The remaining 1-2% is a mix of “unsaponifiable” compounds. Glyceride and triglyceride fractions differ in the nature of their fatty acids and/or for the position that they occupy. Fatty acids, according to their level of saturation by the hydrogen atoms are divided into saturated and unsaturated fatty acids. Fatty acids are all the fats that are found in nature in solid form (very common in animal fats), whilst unsaturated fats are found in liquid form at room temperature and are represented by monounsaturated and polyunsaturated fats depending on the presence of one or two double bonds (double bonds produce greater fluidity, lower the melting point and reduce the stability of the oil as it more easily bonds with oxygen). An analysis of the acidic composition of olive oil shows that the monounsaturated fraction, represented by the oleic acid, is the most abundant (up to 83%) and all the others present much lower percentages. For example saturated fatty acids such as palmitic and stearic acid, are present in olive oil with values of 5.7-18.6% and 0.5-4.0% respectively. Linolenic and linoleic acid prevail amongst all the polyunsaturated fatty acids in olive oil. They are generally known as “Essential fatty acids” (EFA) as they are indispensable for the growth and functioning of tissue, which man is not capable of synthesising. respectively the percentages are 0.1-0.6% and 3.5-20.0%.
The high content of monounsaturated fatty acids is what distinguishes olive oil from other vegetable fats.
Unsaponifiable fraction: the lesser constituents of olive oil, termed unsaponifiable, represent 1.2% of the total.
This is the component that differentiates this product from other liquid fats and includes about 220 substances.
Some of these constituents of olive oil have therapeutic properties, others account for the aroma of the oil (perfumes-tastes) and others still are effective natural antioxidants which help the product resist the effects of ageing.
These most notably include: hydrocarbons, phenolic compounds, alcohols, sterols, coloured pigments and secondary elements.
Hydrocarbons: these account for about 60% of unsaponifiable constituents, and of these, 60-70% is made up of squalene (saturated hydrocarbon) that effects the nutritional properties of oils, whilst the remainder plays an important role in establishing the authenticity and quality of the product.
Tocophenols: in olive oil α, β, γ and δ tocophenols are present. 90% are α tocophenols, which are those that are biologically most active and known as vitamin E.
Tocophenols are natural antioxidants that inhibit rotting.
In order to perform this function the ratio of vitamin E (mg) and polyunsaturated acids (g) is no less that 0.79mg/g.
Sterols: every different species of oleaginous plant has a different percentage of sterolic fraction.
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n olive oil, where the β-sitosterol fraction prevails, the following sterols have been identified: cholesterol (prevalent in animal fats), campesterol, uvaol, stigmasterol, clerosterol, erythrodiol and β-sitosterol
These compounds serve as natural antioxidants, and they also ascertain the authenticity of the product as the sterolic fraction is different for every type of oleaginous plant
Phenolic compounds: phenolic compounds in olive oil are different from those contained in olives and their quality and quantity is heavily influenced by variety, point of ripeness at picking and extraction process.
During extraction, as polyphenols are water-soluble, a substantial part of them are removed with the vegetation water.
It is also well-known that the enzymatic reaction that takes place during extraction cause the molecules to split into simpler particles than those found in olives.
Oils from virgin and extra virgin olives are the only vegetables fats that naturally contain appreciable quantities (50-500mg/kg) of phenolic substances.
Reference to virgin oils is not by chance because whatever type of chemical intervention that is carried out on this product cannot completely destroy its natural phenolic properties.
The antioxidant power of polyphenols, highlighted by some scholars, has consolidated the important effect that these compounds have on the stability of olive oil.
The literature is full of information that underlines the positive link between quantity of total polyphenols in virgin oils and resistance over time to oxidation (induction period).
Furthermore, scholars have highlighted the synergic action between polyphenols and α-tocophenols (vitamin E) on the stability of virgin olive oil.
Coloured pigments: these provide the colour characteristics of olive oil.
They are made up of chlorophylls and carotenoids.
Types a and b chlorophylls give freshly extracted oils their intense green colour.
They can oscillate between 0 and 10 ppm, and they themselves vary according to cultivar and point of ripeness of the fruit.
These substances merit attention because in the presence of light they act as pro-oxidants, whilst in the dark they act in synergy with phenols to protect the oil from oxidation.
Alcohols: oil contains aliphatic and triperpenic alcohols.
They are esterified in wax and they are very important in analysis for the identification of oils obtained through extraction with solvents or through mechanical pressure.
Other secondary elements: aldehydes, esters, ketones, etc, that influence the aromatic note of the oil and thus the compounds involved in its hedonistic evaluation.
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