The evergreen olive tree (Olea europea L.) belongs to the family Oleaceae. It reaches a height of 10-16 meters and has a typical gnarled / furrowed bark. The plant prefers a frost-free, mild climate without extreme climate fluctuations. Porous calcareous soils with a low waterlogging level are advantageous here, as root rot can quickly lead to tree damage. It is therefore not surprising that the olive tree is native to the European Mediterranean area, South Africa or the Middle East with dry summers and frost-free winters.
Although it has a longevity of over 1000 years, the very slow growing olive tree only starts to bear its fruits after 10 years. The fruit (2-12g) is a drupe which consists of the following layers (from the outside to the inside): wax-coated epicarp, mesocarp with bitter substances, endocarp with lignin and kernel. The quality and quantity of the oil, which is mainly found in the mesocarp, is determined by the different composition of these layers.
2. Origin/flowering time/harvest
The olive tree prefers a subtropical climate. The world's largest area of cultivation and consumption is the European Union (EU), with Spain, Italy, Greece and Turkey among the largest producers.
Depending on the geographical location, the flowering period starts in spring.
Harvesting is done on small farms by hand or by laying out nets. In the latter case, the olives are beaten off the branch and fall onto the net, making them easier to collect. In case of intensive cultivation, full harvesting machines are used, which shake the entire tree and catch the falling olives in nets.
Olive oil has many different qualities due to the different harvesting, pressing and processing methods.
The manufacturing processes are subdivided according to the processing of the fruit: Olive oil can be obtained either from the whole olive, the pulp or the core.
a) The "Virgin Olive Oils", upper group of edible oils, are produced by way of mechanical or other physical procedures (which do not lead to an oil deterioration). Mixtures with other oils and further post-treatment such as refining etc. are not permitted. In order to further differentiate the chemical composition and olfactory requirements, subcategories have been divided into "Extra virgin olive oil", "Virgin olive oil" and "Lampant oil".
"Extra virgin olive oil" (category 1) has the highest olfactory requirements and the lowest free fatty acid content (maximum 0.8g per 100g oil).
The "Virgin Olive Oil" (category 2) has slightly lower demands in both respects: odour and taste are slightly weaker, with free fatty acids under 2g per 100g oil.
Lampant oil (category 3) is not suitable for consumption with over 2.0g per 100g of free fatty acids and needs further processing. By refining "refined olive oil"emerges (category 4).
b) In order to obtain a higher oil yield, press preparation steps are conducted at high pressure/temperature. The obtained "pressed oil" is of low quality or contains undesirable accompanying substances which is why it must be further processed in additional steps. By refining it, the "Refined Olive Oil" is obtained. "Refined Olive Oil" is obtained from "Lampant Oil" or "Pressed Oil" by refining. Its content of free fatty acids is adjusted to a maximum of 0.3g per 100g oil. Although this seems very low, several important substances have already been removed from the oil by refining. The result is a pure oil, with specifically adjusted parameters.
c) As already mentioned, there is still a residual oil content in the olive pomace. This content can be further reduced to a minimum by using solvents or physical methods.
"Crude olive-pomace oil" (category 6) is the first intermediate product and is similar in quality to lampante olive oil.
If the "crude olive-pomace oil" is further refined, "refined olive-pomace oil" (category 7) is obtained with a maximum fatty acid content of 0,3 g per 100 g.
4.The following oils can be obtained by blending oils:
(a) “Olive oil - (composed of refined olive oil and virgin olive oil)” (category 5) is a blend of “refined olive oil” and “virgin olive oil” (except lampante olive oil) in any proportion, with a maximum free acidity content of at most 1,0 g per 100 g oil.
(b) "Olive-pomace oil" (category 8) is a blend of "refined olive-pomace oil" and "virgin olive oils" (except lampante olive oil) in any proportion, with a maximum free fatty acids of 1,0 g per 100 g oil.
Olive oil is rich in saturated fatty acids, polyphenols, squalene, vitamin E and phytosterols. Many of these substances have a positive effect on the immune system and even show anticarcinogenic properties.
The oil can be used as a laxative in two ways: rectally applied to soften stools or orally as a stimulus to the intestinal mucosa.
Olive oil or in general oils with high content of saturated fatty acids seem to have a positive effect on blood lipid values. Diseases such as arteriosclerosis, coronary heart disease or diabetes can thus be positively affected.
In pharmacy, olive oil is used perorally, percutaneously and topically. Due to the lipophilicity of the oil and its low penetration capacity into the skin, the oil can be used to cleanse the skin. Crusts occurring in eczema and psoriasis as well as adhering lipophilic substances (e.g. ointments) can be removed more easily. In topical and peroral application, the oil can be used as a solvent for lipophilic drugs. Olive oil can be heat sterilized, which is why it is also suitable for percutaneous application.
Although olive oil is difficult to absorb into the skin it is widely used in the cosmetic industry due to its antimicrobial properties.
Due to its high content of unsaturated fatty acids, the oil is often used as edible oil, cooking oil and frying oil. For the end user only 3 categories are important in the range of edible oils: "extra virgin olive oil"; "virgin olive oil" and "olive oil".
5. Further properties/facts
1. The olive tree has to battle not only with fungal infestation and several harmful insects, but also against harmful "Xylella fastidiosa" bacteria. These bacteria, which also occur in vines or other citrus plants, are usually transmitted by insects and lead to the complete death of the olive tree within a few years. This leads to a kind of vascular disease in which the plant is no longer supplied with sufficient nutrients and consequently dies off. To stem this disease, the plants are usually completely cleared. The latest treatment methods use a mixture of copper and zinc, which can lead to regeneration of the plants. Experimental methods test pomegranate extract or heat to keep the bacteria in check. If more oils are imported from the affected areas, the general limits for copper, zinc and pesticides in food should be reviewed.
2. Pharmaceutical products must not be made from olive oil obtained by extraction. Markers can be: wax esters, triterpene alcohols (erythrodiol or uvaol) and the unsaponifiable fraction.
3. Olive oils are often blended with lower quality olive oils to save costs. The stigmastadiene value is helpful for this. It indicates a degradation product of refining and must not exceed a value of 0.05mg/kg. If the values of "native oils" are above this limit, the oil has been stretched with refined oil.
4. Another indicator of the quality of the olives and the conditions of production is the chemical group of fatty acid alkyl esters. These products are formed when olives are incorrectly stored and utilized. One value is the fatty acid ethyl ester, which should not exceed 35 mg/kg.
5. Olive oil should not be stored too warm or too cold. For example, if the oil is stored in the refrigerator, (reversible) flocculation occurs.