The olive tree’s fruit, an olive, is of major agricultural importance in the Mediterranean region as the source of olive oil.
Olives are one of the core ingredients in Mediterranean cuisine.
Thousands of cultivars of the olive tree are known.
Olives cultivated for consumption are generally referred to as table olives.
About 90% of all harvested olives are turned into oil, while about 10% are used as table olives.
The olive tree, Olea europaea, is an evergreen tree or shrub native to Mediterranean Europe, Asia, and Africa.
The olive tree is short and squat and rarely exceeds 8–15 m (25–50 ft) in height.
Its silvery green leaves are oblong, measuring 4–10 cm (1+1⁄2–4 in) long and 1–3 cm (3⁄8–1+3⁄16 in) wide.
The trunk is typically gnarled and twisted.
The fruit is a small drupe 1–2.5 cm (3⁄8–1 in) long when ripe.
Olives are harvested in the green to purple stage.
Olea europaea contains a pit.
The six natural subspecies of Olea europaea are distributed over a wide range.
Hundreds of cultivars of the olive tree are known, impacting on its color, size, shape, and growth characteristics, as well as the qualities of olive oil.
Olive cultivars may be used primarily for oil, eating, or both.
Since many olive cultivars are self-sterile or nearly so, they are generally planted in pairs with a single primary cultivar and a secondary cultivar selected for its ability to fertilize the primary one
For thousands of years olives were grown primarily for lamp oil, with little regard for culinary flavor.
The olive branch has often been a symbol of abundance, glory, and peace, and has also been used to symbolize wisdom, fertility, power, and purity.
About 90% of all harvested olives are turned into oil, while about 10% are used as table olives.
The olive is one of basic ingredients in Mediterranean cuisine, the other two being wheat for bread, pasta, and couscous; and the grape for wine.
Olive oil is a liquid fat obtained from olives, produced by pressing whole olives and extracting the oil.
Olive oil is commonly used in cooking, for frying foods or as a salad dressing.
It is used in cosmetics, pharmaceuticals, and soaps, and as a fuel for traditional oil lamps, and has additional uses in some religions.
Spain accounts for almost half of global olive oil production; other major producers are Portugal, Italy, Tunisia, Greece and Turkey.
Per capita consumption is highest in Greece, followed by Italy and Spain.
The composition of olive oil varies with the cultivar, altitude, time of harvest and extraction process.
Olive oil consists mainly of oleic acid, up to 83%, with smaller amounts of other fatty acids including linoleic acid, up to 21%, and palmitic acid, up to 20%.
Extra virgin olive oil is required to have no more than 0.8% free acidity and is considered to have favorable flavor characteristics.
Raw or fresh olives are naturally very bitter.
To make olives palatable, they must be cured and fermented, thereby removing oleuropein, a bitter phenolic compound that can reach levels of 14% of dry matter in young olives.
In addition to oleuropein, there are other phenolic compounds present that make freshly picked olives unpalatable and must also be removed or lowered in quantity through curing and fermentation.
Phenolics reach their peak in young fruit and are converted as the fruit matures.
Once ripening occurs, the levels of phenolics sharply decline through their conversion to other organic products which render some cultivars edible immediately.
Table olives which can be stored without refrigeration.
Fermentations dominated by lactic acid bacteria are the most suitable method of curing olives.
It is most commonly applied to green olive preparation, around 60% of all the world’s table olives are produced with this method.
Olives are soaked in lye for 8–10 hours to hydrolyse the oleuropein.
They are then washed once or several times in water to remove the caustic solution and transferred to fermenting vessels full of brine at typical concentrations of 8–12% NaCl.
Fermentation is carried out by the natural microbiota present on the olives that survive the lye treatment process.
Yeasts then accumulate in sufficient numbers to help complete the fermentation alongside the lactic acid bacteria.
Once fermented, the olives are placed in fresh brine and acid corrected, to be ready for market.
Olives like hot weather and sunny positions without any shade, while temperatures below −10 °C (14 °F) may injure even a mature tree.
They tolerate drought well because of their sturdy and extensive root systems.
Olive trees can remain productive for centuries as long as they are pruned correctly and regularly.
Only a handful of olive varieties can be used to cross-pollinate.
The preferred ways to propagate olives are cuttings and layers; the tree roots easily in favorable soil and throws up suckers from the stump when cut down.
Yields from trees grown from suckers or seeds are poor; they must be budded or grafted onto other specimens.
Olive is an invasive species.
Most olives today are harvested by shaking the boughs or the whole tree.
Olives are one of the most extensively cultivated fruit crops in the world.
Olives, green
Nutritional value per 100 g (3.5 oz)
Energy
609 kJ (146 kcal)
Carbohydrates 3.84 g
Sugars 0.54 g
Dietary fiber 3.3 g
Fat 15.32 g
Saturated 2.029 g
Monounsaturated 11.314 g
Polyunsaturated 1.307 g
Protein 1.03 g
Vitamins
Quantity %DV†
Vitamin A equiv.-3% 20 μg
beta-Carotene-2%231 μg
lutein zeaxanthin-510 μg
Thiamine (B1)-2% 0.021 mg
Riboflavin (B2)-1% 0.007 mg
Niacin (B3)-2% 0.237 mg
Vitamin B6 2% 0.031 mg
Folate (B9) 1% 3 μg
Choline 3% 14.2 mg
Vitamin E 25% 3.81 mg
Vitamin K 1% 1.4 μg
MineralsQuantity %DV
Calcium 5% 52 mg
Iron 4% 0.49 mg
Magnesium 3% 11 mg
Phosphorus 1% 4 mg
Potassium 1% 42 mg
Sodium 104% 1556 mg
Water 75.3 g
One hundred grams of cured green olives provide 146 calories, are a rich source of vitamin E (25% of the Daily Value, DV), and contain a large amount of sodium (104% DV); other nutrients are insignificant.
Green olives are 75% water, 15% fat, 4% carbohydrates and 1% protein.
The polyphenol composition of olive fruits varies during fruit ripening and fermentation when olives are immersed whole in brine or crushed to produce oil.
Polyphenol contents are 117 mg/100 g in black olives and 161 mg/100 g in green olives, compared to 55 and 21 mg/100 g for extra virgin and virgin olive oil, respectively.
Olive fruit contains several types of polyphenols, mainly tyrosols, phenolic acids, flavonols and flavones, and for black olives, anthocyanins.
Its main bitter flavor of olives before curing from oleuropein and its aglycone which total in content, respectively, 72 and 82 mg/100 g in black olives, and 56 and 59 mg/100 g in green olives.
Olive tree pollen is extremely allergenic,
Olea europaea is primarily wind-pollinated and its light, buoyant pollen is a strong trigger for asthma.