Olive (Olea europea L.)

 

Branch with ripe olives www.botanikus.de

Used plant part

The fruit (a drupe), which is pale green when unripe and purple to black when ripe. The fruits are normally sold pickled in brine, or used to extract olive oil.

The leaves of the olive tree are used medicinally for their hypotensive qualities.

Plant family

Oleaceae (olive family).

Sensoric quality

Raw olives are very bitter, but after several months in brine, the bitterness vanishes, and a characteristic aroma develops. Native olive oil has a pleasant, fruity fragrance; it affects the character of any dish cooked therewith.

Main constituents

In leaves and fruits of the olive tree, a phenolic seco-iridoid called oleuropein is found; it is the hypotensive principle. Before pickling olives, the oleuropein is removed either by treatment with lye or by lactic fermentation; the remaining residues of oleuropein are sometimes said to prevent diseases resulting from high blood pressure.
 

Olives in various stages of ripening mypage.bluewindow.ch

Olive oil is obtained from the mesocarp of special varieties of olives with rather small fruits; the mesocarp contains about 55% of oil. Oil obtained from the first pressing (called extra vergine in Italy, elsewhere "native olive oil extra") is produced at low temperature and at low pressure (max. 50 bar); it is usually pale greenish-yellow and strongly scented. Later cold pressing at higher pressure yields the so-called "native olive oil", which is less aromatic. The fraction of oil not available by cold pressure is about 25%; it can be won both by high temperature and by solvent extraction, but it cannot be used for human consumption without further raffination steps.

Olive oil is composed, like all plant oils (see also sesame), of fatty acids bound to the alcohol glycerol. Typically, the following fatty acids are found in olive oil: 66% elaic acid, 12% linoleic acid, 9% palmitic acid, 5% eicosenoic acid and 5% palmitoleic acid. The green colour is caused by chlorophyll (up to 10 ppm). Olive oil may contain up to 1.5% of an acyclic triterpene hydrocarbon, squalene.

Origin

Cultivation of the olive tree is known in the Eastern Mediterranean since five millennia. Whether the plant really stems from these regions or is a native to Central Asia is subject to debate.
 

Olive branch with unripe fruits

Etymology

Olive is a loan from Latin oliva "olive; olive tree", which itself was loaned from Greek (eláa or elaía, from older elaíva "olive; olive tree"; furthermore élaion "olive oil"). The word's ultimate origin is probably an Eastern Mediterranean language not known today.

In the languages of the Iberic peninsula, the Latin name was superseeded by an Arabic loan: Spanish aceituna and Portuguese azeitona both come from Arabic al-zeytun "the olive"; in Spanisch, oliva refers to the tree, not to the fruit. See also capers for more examples of Arabic loans in Iberic languages.

The Arabic term is cognate to Hebrew zayith "olive" and might derive from a Common Semitic root signifying "to be prominent".

Due to the enormous importance of olives for both the Greek and the Roman cultures, their name entered nearly every European language via Latin oleum "oil" as generic word for liquid fats.

 

 

Olive tree www.botanikus.de

It is difficult to name any plant of more cultural and historic significance to the Mediterranean than the olive. Egyptians, Phoenicians, Greeks and Romans knew and valued olive oil. The olive tree is mentioned in the Homeric epics (see poppy) and olive branches were used, in oldest time, to decorate the winners of the Olympic Games; later, they were replaced by bay leaves. In the classic era of Greece, the olive was closely associated with the goddes Pallas Athene, a daughter of Zeus. Innumerous are the instances of olive in the Bible, both in the Old and the New Testament (see pomegranate). The old Romans used olive oil extensively (see also silphion).

Olives are grown in the whole Mediterranean region and are a most important part of the diet in all Mediterranean countries: Olive oil is ubiquitously used as a cooking medium, and pickled olives are popular both a spice and as a snack.

Pickled olives are either black or green, depending whether they have been harvested unripe or ripe. Green olives are plucked unripe and treated with concentrated lye before pickling; by this procedure, which dated back to ancient Rome, bitterness is greatly reduced and the texture is improved. Black olives are plucked ripe; in Greece, they are treated with salt or undergo lactic fermentation, which results in an intense flavour. The brine olives are pickled in is often further enhanced by addition of some herbs (thyme, oregano) or garlic.

Pickled olives are a common decoration for cold dishes and tasty sauces. Of course, they fit best to specialities from the Mediterranean. Olive's flavour can be enhanced by preparing a paste of finely cut and squeezed olives with good olive oil. Adding anchovis (fermented fish), garlic and optionally capers to such a paste from black olives and olive oil gives tapenade, a Southern French speciality which tastes best with crunchy baguettes.

The use of olives for warm dishes is more or less restricted to Mediterranean cuisines. Tomato sauces containing onion, garlic, capers and green (or sometimes black) olives are characteristic of Italy; they may be made even tastier by adding fresh herbs (basil, oregano and rue). Sauces of this kind may be used to cook meat or poultry or they can simply be served together with noodles (pasta). Italian pizza is often prepared with (usually black) olives, mostly so in Southern Italy (see oregano).

Far more important than pickled olives is, however, olive oil, whose production consumes about 90% of olive acreage. The best quality, native olive oil extra (in Italy known as extra vergine), is quite variable in appearance and taste; after having tried some oils, most people develop different preferences. Some oils are subtle and flowery, others intense and fruity. It is probably a good idea to stock a few different varieties in the kitchen. Oils from second pressing is less aromatic, but better suited for frying. If you want to fry in extra vergine olive oil, the smoke point is raised by mixing the oil with butter, which might improve flavour anyway.

Many of the dishes of Southern Europe, Western Asia and Northern Africa owe much of their character to extra vergine olive oil. It is used for salads, for the Near East chick pea paste hummus (see sesame), cold appetizers (in Israel collectively known as mezes), spice pastes like Egypt dukka (see thyme) or the famous Provençal garlic mayonnaise aïoli. Italian noodles (pasta) are often boiled with a spoonful of olive oil to prevent them from sticking together; before serving, olive oil is often added to increase the flavour.

By using olive oil instead of characterless vegetable oil, everyday dishes like shallow-fried vegetables (zucchini, aubergines, capsicum) get a typically Mediterranean character, even more if they are served with yoghurt or tomato sauce. Another trick is to sprinkle high-quality olive oil over fried vegetables and fish before serving.

The taste of olive oil harmonizes excellently with the fragrance of Mediterranean herbs. In the Mediterranean countries, olive oil is often flavoured with branches of rosemary, lavender, tarragon or, on Cyprus, with fresh capers. Most fresh herbs can be preserved in olive oil; their aroma compounds dissolve better in oil than in an aqueous medium. A most famous recipe of this kind is pesto, a paste of ground basil leaves in olive oil.

Not only the gentle fragrance of fresh herbs, but also the pungency of chiles has an affinity for a fatty medium. In Italy, small but powerful chiles (peperoncini) are often used to convert olive oil to a fiery condiment. I have seen a comparable chile oil in Arizona. According to personal taste, it may be used drop by drop or tablespoon by tablespoon. In some variants of the Yemeni condiment zhoug (see coriander), the heat of green chiles is transmitted by olive oil.