The Olive (Olea europaea) is a small evergreen tree that grows best in a Mediteranean climate. Spain, Italy, Greece, and other Mediterranean countries are major producers, but olives are also cultivated outside the Mediterranean region in regions with an appropriate climate (e.g., in in California and Argentina). The olive fruit has a skin, a fleshy pulp, and a stony kernel. As the fruit matures, it turns from green to black.
Some archaeological evidence suggests that the Olive may have been domesticated in the eastern Mediterranean region 10,000 years ago. Certainly, this species has been closely associated with human religious, cultural, medical, and food uses for thousands of years. As food, olives are used both for their edible pulp (which contains up to 40% or more oil, in contrast to the kernel, which contains only a small amount of oil) and as the source of olive oil. The oil is monounsaturated, with a high percentage of the fatty acid oleic acid. Olive oil is used as a cooking oil, in salad dressings, and as a food preservative; in some places, such as the United Kingdom, it is used in a spread. Olive oil is also used in cosmetics and in the pharmaceutical industry, among other applications. Olives are cold-pressed and the first pressings, which require no further treatment, are known as "virgin" ("extra virgin" olive oil is virgin oil that has a specified low acidity). The residue left after pressing (pomace) is used in animal feed.
Both green (immature) and black olives are pickled in brine. These olives contain less oil than those used for oil extraction. Prior to pickling, the bittter glycoside oleuropein is often neutralized with caustic soda or another lye solution. During processing, the olives may have their pits removed and sometimes replaced with pimentos, garlic (Allium sativum), or some other filling.
Olive pollen is one of the most important causes of seasonal respiratory allergy in Mediterranean countries. In addition, cases of contact dermatitis and food allergy to the olive fruit and olive oil have been described. (Rodriguez et al. 2001; Esteve et al. 2012)
The Olive Fruit Fly (Bactrocera oleae) is an important economic pest wherever olives are grown (Daane and Johnson 2010). The historical biogeography of this fly, and its evolving relationship with O. europea, have been investigated by Nardi et al. (2010).
Feral Olive trees are significant weeds in Hawaii, Norfolk Island, and Australia (Spenneman and Allen 2000; Cuneo et al. 2010).
(Vaughan and Geissler 1997)