According to Italian legislation, olive oil is the product of the pressing of the fruits of European olea Leccino.
European olea Leccino - Olive tree
The "Olea europea, commonly called olive tree, is a plant belonging to the oleaceae family which further differs into two botanical species: Olea europea sativa and European oleaster (more than 30 wild species).
"Italy is a strongly olive growing nation, so much" that, on a theoretical level, only two regions out of twenty (Piedmont and Valle d "Aosta) are NOT characterized by the cultivation (even minimal) of the olive tree; moreover, as is easily understood, most of the Italian oil comes from the south of the peninsula (85% of the total): Puglia, Calabria, Basilicata, Sicily and Sardinia.
Curiosity: The olive tree is the plant subject to fluctuations in production par excellence; it is characterized by years of poor yield (called charge) followed by years of high vegetative and fruiting production (called discharge).
Olive
The fruit or drupe of the Olea europea sativa is defined olive; the olive is characterized by a weight that varies between 1.5 and 4.5 grams and is structurally composed of:
- Epicarp or peel 1.5-3%: it is a thin and elastic outer membrane (epidermis) of variable color according to the state of ripeness (from chlorophyll green to red or black - anthocyanins), covered by a protective waxy substance, the bloom (with function of protective screen against parasites and microorganisms)
- Pulp 70-80%: it has a fleshy consistency and variable color; it mainly contains water and esterified lipids (oil).
- Endocarp or stone 15-25%: it is a woody "shell" that encloses the seed also called "almond" (achene - 2.5-4% of the weight). The core is in turn divisible into endosperm, episperm and embryo
NB. the achene of the olive is indehiscent for the human intestine.
Ripe Olive Nutritional Values
The mature olive, therefore ready to be pressed for the production of oil, has a chemical composition that can be summarized as follows:
- Water 45-55%: it is the component most present in the fruit
- Lipids 13-28%: portion useful for the composition of the oil
- Nitrogen substances 1,5-2%:
- Non-nitrogenous compounds 18-24%
- Crude fiber 5-8%
- Ash 1-2%
Types of oil
The types of oil obtained from olive harvesting and pressing can be classified into 3 groups:
- Oils obtained by mechanical means; there are three, but of these only two are directly edible: the extra virgin and the Virgin. The third, said glaring (because it was once used as a fuel for lamps) to become edible it requires a refining process.
In 2003, a fourth was defined, said current virgin, not available at retail and used only industrially for blends and blends of other oils. - Oil refined glare: purified by means of chemical-physical procedures to eliminate the NON-edible components. By mixing it with virgin oil, it is marketed under the name of olive oil.
- Oils extracts with chemical solvents from processing residue (pomace); they too are refined and subsequently blended with virgin oils to be marketed under the name of pomace oil.
Methods of olive harvesting
The methods of olive harvesting are many and different from each other; they are variable techniques for: level of automation, level of manpower, quality of the selection and result of the harvest. The methods are:
- Harvesting, which in turn includes:
- Spontaneous fall
- Combing
- Shaving of the olives
- Harvesting
- Hand picking
Extraction techniques
There are three techniques for extracting olive oil:
- PRESSURE (classic and discontinuous method)
- CENTRIFUGATION (modern and continuous method)
- PERCOLATION by SELECTIVE FILTRATION
In the various techniques of olive oil extraction it is possible to identify a common initial phase, namely:
'Cleaning initial of the drupes and the subsequent milling or pressing; the latter corresponds to a real grinding of the fruits in order to obtain an emulsion of water and lipids. On this emulsion is then applied the kneading, a procedure aimed at a "further separation of the lipid fraction into larger" oily drops "; it is carried out by rotating metal (steel) helical blades inside a tank.
Extraction by pressure includes a series of well-determined phases characterized by discontinuity.
One is applied to the malaxed compound pressing which separates the liquid portion from the pomace. The resulting fluid must then be centrifuged (centrifugation) in order to obtain a first separation of the water from the oil; the eliminated portion is defined as vegetation water. The resulting compound is then subjected to filtration from which it is obtained l "virgin olive oil.
Extraction by centrifugation, on the other hand, is made up of a single and continuous procedure which allows to obtain at the same time all three final components; NB. Extraction by centrifugation has a high cost in terms of energy.
The centrifugal extraction of the kneaded material exploits the difference of the 3 specific weights obtaining separately but continuously: pomace, virgin olive oil and vegetation water.
The extraction by percolation and selective filtration adopts a different physical process; this technique uses the higher surface tension of the oil compared to that of water.
A large sheet of steel is immersed in the malaxer which, with regard to the difference in surface tension between the two fluids, is mainly wetted with oil; this is then removed and drained into another container.
Leachate can originate oil and must, subsequently centrifuged to extract more oil to the detriment of the vegetation water. Or it can generate oil and non-definitive pomace, from whose centrifugation must be obtained (treated as just described) e pomace.
Either method is applied on the basis of the type and effectiveness of percolation.
Virgin oil VS extra virgin olive oil
Notice how the oily extraction product is repeatedly called Virgin and not extra virgin; this is because, from a technical production point of view, extra virgin olive oil does NOT differ from virgin; on the contrary, what (severely) differentiates the two products is the set of chemical and organoleptic characteristics. It is true that "extra virgin olive oil CAN" be obtained with first cold pressing (at less than 27 ° C by means of a first mechanical pressing carried out on the malaxer with hydraulic presses) or simply with cold extraction (at less than 27 ° C by percolating or centrifuging the malaxate); however, although these characteristics also contribute to conferring a higher or lower quality of production, nothing comes with the specific production disciplinary drawn up by the European Community (EC Reg. 1989/2003).
To acquire the denomination exta, a virgin olive oil MUST have a "MAXIMUM total acidity (induced by" free oleic acid, therefore NOT esterified with glycerol) equal to 0.8%; on the other hand, a NON extra virgin oil can use a "NOT" acidity more than 2%.
In addition to the chemical analysis, it is essential that the extra product passes the organoleptic control through a test applied and verified by the competent control bodies; the most important characteristics evaluated are: the fruity aroma (induced by the volatile components) and the taste bitter and spicy (conferred by polyphenols).
Chemical composition
It is possible to distinguish the composition of the "olive oil" in two fractions:
- Saponifiable fraction: it is composed of 98-99% triglycerides, 55% simple and 45% mixed, respectively. The fatty acid composition is variable but fundamentally it is distinguished by the high intake of palmitic (saturated), oleic (monounsaturated and predominant over the others), linoleic (polyunsaturated) and linolenic (polyunsaturated) acids.
A good olive oil SHOULD be characterized by: oleic acid not lower than 73%, linoleic acid not higher than 10% and an oleic / linoleic ratio > 7. - Unsaponifiable fraction: it is composed of hydrocarbons (including squalene 0.3-0.6%), phytosterols (β-sitosterol, campesterol, stigmasterol), fat-soluble vitamins (3-3.7%, represented by β-carotene and tocopherols, all antioxidants), pigments (chlorophyll and carotenoids), higher aliphatic alcohols esterified to fatty acids (waxes and triterpene alcohols), polyphenols (2-3%, represented by glucosides and esters, also antioxidants)
Nutritional properties of "extra virgin" olive oil
Bibliography:
- Food chemistry - P. Cabras, A. Martelli - chap 10
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