Olive tree, oil and and fruit, has its blessings from God.

The olive is a species of small tree, found in much of Africa, the Mediterranean Basin from Portugal to the Levant, the Arabian Peninsula, and southern Asia as far east as China, as well as the Canary Islands, Mauritius and Réunion. The species is cultivated in many places and considered naturalized in Algeria, France (including Corsica), Greece, Turkey, Cyprus, Malta, Croatia, Albania, Crimea, Egypt, Iran, Iraq, Israel, Italy, Jordan, Spain, Palestine, Syria, Lebanon, Java, Norfolk Island, California and Bermuda.

The olive's fruit, also called the olive, is of major agricultural importance in the Mediterranean region as the source of olive oil. The tree and its fruit give their name to the plant family, which also includes species such as lilacs, jasmine, Forsythia and the true ash trees (Fraxinus). The word derives from Latin ŏlīva ("olive fruit", "olive tree"; "olive oil" is ŏlĕum) which is cognate with the Greek (elaía, "olive fruit", "olive tree") and  (élaion, "olive oil"). The word "oil" in multiple languages ultimately derives from the name of this tree and its fruit.

Historical Evidence
It is almost certain that the olive tree as we know it today had its origin approximately 6,000 -7,000 years ago in the region corresponding to ancient Persia and Mesopotamia. The olive plant later spread from these countries to nearby territories corresponding to present-day Syria and Palestine

The edible olive seems to have coexisted with humans for about 5000 to 6000 years, going back to the early Bronze Age (3150 to 1200 BCE). Its origin can be traces to areas along the eastern Mediterranean Coast in what are now southern Turkey, Syria, Lebanon, Palestine, and Israel based on written tablets, olive pits, and wood fragments found in ancient tombs, a cook book writer quoted that the most ancient evidence of olive cultivation having been found in Syria, Israel, and Crete.

It is assumed that Olive tree plants may have arisen from O. chrysophylla in northern tropical Africa and that it was introduced into the countries of the Mediterranean Basin via Egypt and then Crete or the Levant, Syria, Tunisia and Asia Minor. Fossil Olea pollen has been found in Macedonia, Greece, and other places around the Mediterranean, indicating that this genus is an original element of the Mediterranean flora. Fossilized leaves of Olea were found in the palaeosols of the volcanic Greek island of Santorini (Thera) and were dated about 37,000 BP. Imprints of larvae of olive whitefly Aleurolobus (Aleurodes) olivinus were found on the leaves. The same insect is commonly found today on olive leaves, showing that the plant-animal co-evolutionary relations have not changed since that time.

As far back as 3000 BC, olives were grown commercially in Crete; they may have been the source of the wealth of the Minoan civilization.

Outside the Mediterranean
Olives are not native to the Americas. The Spanish colonists brought the olive to the New World where its cultivation prospered in present-day Peru and Chile. The first precious seedlings from Spain were planted in Lima by Antonio de Rivera in 1560. Olive tree cultivation quickly spread along the valleys of South America's dry Pacific coast where the climate was similar to the Mediterranean. The Spanish missionaries established the tree in the 18th century in California. It was first cultivated at Mission San Diego de Alcalá in 1769 or later around 1795. Orchards were started at other missions but in 1838 an inspection found only two olive orchards in California. Oil tree cultivation gradually became a highly successful commercial venture from the 1860s onward. In Japan the first successful planting of olive trees happened in 1908 on Shodo Island which became the cradle of olive cultivation. It is estimated that there are about 865 million olive trees in the world today (as of 2005), and the vast majority of these are found in Mediterranean countries, although traditionally marginal areas account for no more than 25% of olive planted area and 10% of oil production.

Peace symbols
Olive oil has long been considered sacred. The olive branch was often a symbol of abundance, glory and peace. The leafy branches of the olive tree were ritually offered to deities and powerful figures as emblems of blessings and purification, and they were used to crown the victors of friendly games and bloody wars. Today, olive oil is still used in many religious ceremonies. Over the years, the olive has been the symbol of peace, wisdom, glory, fertility, power and purity.

Ancient Egypt
Leafy branches of the olive tree were found in Tutankhamun's tomb.

In Islam
Suratul - At - tin 95: 4, Allah mentioned the Olive, it can cure almost all diseases except death.

Ancient Israel and Hebrew Bible
The olive was one of the main elements in ancient Israelite cuisine. Olive oil was used for not only food and cooking, but also lighting, sacrificial offerings, ointment, and anointment for priestly or royal office.

The olive tree is one of the first plants mentioned in the Hebrew Bible and in the Christian Old Testament, and one of the most significant. It was an olive leaf that a dove brought back to Noah to demonstrate that the flood was over (Book of Genesis, 8:11). The olive is listed in Deuteronomy 8:8 as one of the seven species that are noteworthy products of the Land of Israel.

Ancient Greece
The ancient Greeks used to smear olive oil on their bodies and hair as a matter of grooming and good health.

Olive oil was used to anoint kings and athletes in ancient Greece. It was burnt in the sacred lamps of temples as well as being the "eternal flame" of the original Olympic Games. Victors in these games were crowned with its leaves.

Odysseus crawls beneath two shoots of olive that grow from a single stock and metaphoric description of a lone olive tree in the mountains, by a spring; the Greeks observed that the olive rarely thrives at a distance from the sea, which in Greece invariably means up mountain slopes. Greek myth attributed to the primordial culture-hero Aristaeus the understanding of olive husbandry, along with cheese-making and bee-keeping. Olive was one of the woods used to fashion the most primitive Greek cult figures, called xoana, referring to their wooden material; they were reverently preserved for centuries. It was purely a matter of local pride that the Athenians claimed that the olive grew first in Athens. In an archaic Athenian foundation myth, Athena won the patronship of Attica from Poseidon with the gift of the olive. Though, according to the 4th-century BC father of botany, Olive trees ordinarily attained an age of about 200 years, mentions that the very olive tree of Athena still grew on the Acropolis; it was still to be seen there in the 2nd century AD; and when Pausanias was shown it, c. 170 AD, he reported "Legend also says that when the Persians fired Athens the olive was burnt down, but on the very day it was burnt it grew again to the height of two cubits." Indeed, olive suckers sprout readily from the stump, and the great age of some existing olive trees shows that it was perfectly possible that the olive tree of the Acropolis dated to the Bronze Age. The olive was sacred to Athena and appeared on the Athenian coinage.

On the Nature of Plants, does not give as systematic and detailed account of olive husbandry and that of the vine, but makes clear that the cultivated olive must be vegetatively propagated; indeed, the pits give rise to thorny, wild-type olives, spread far and wide by birds. Theophrastus reports how the bearing olive can be grafted on the wild olive, for which the Greeks had a separate name, kotinos.

Ancient Rome
According to the Romans, a vine, a fig and an olive tree grew in the middle of the Roman Forum; the latter was planted to provide shade (the garden plot was recreated in the 20th century). The Roman poet mentions it in reference to his own diet, which describes as very simple: " olives, endives, and smooth mallows provide sustenance." Since it is  preferred by the ancients and as one of the most perfect foods.

Olive oil
The olive tree, has been cultivated for olive oil, fine wood, olive leaf, and the olive fruit. 90% of all harvested olives are turned in to oil, while about 10% are used as table olives.

Table olives
Table olives are classified by the IOC into 3 groups according to the degree of ripeness achieved before harvesting.

Green olives. 

Picked when they have obtained full size, but before the ripening cycle has begun. Usually shades of green to yellow.

Semi-ripe or turning-colour olives.

 Picked at the beginning of the ripening cycle, when the colour has begun to change from green to multi-colour shades of red to brown. Only the skin is coloured as the flesh of the fruit lacks pigmentation at this stage, unlike that of ripe olives.

Black olives or ripe olives. Picked at full maturity when fully ripe. Found in assorted shades of purple to brown to black.

Traditional fermentation and curing

Raw or fresh olives are naturally very bitter; to make them palatable, olives 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, other phenolic compounds render freshly picked olives unpalatable and must also be removed or lowered in quantity through curing and fermentation. Generally speaking, phenolics reach their peak in young fruit and are converted as the fruit matures. One exception is the throubes olive, which can be eaten fresh. Once ripening occurs the levels of phenolics sharply decline through their conversion to other organic products which renders some cultivars edible immediately.

The curing process may take from a few days, with lye, to a few months with brine or salt packing. With the exception of California style and salt cured olives, all methods of curing involve a major fermentation involving bacteria and yeast that is of equal importance to the final table olive product. Traditional cures, using the natural microflora on the fruit to induce fermentation, lead to two important outcomes: the leaching out and breakdown of oleuropein and other unpalatable phenolic compounds, and the generation of favourable metabolites from bacteria and yeast, such as organic acids, probiotics, glycerol and esters, which affect the sensorial properties of the final table olives. The probiotic qualities of mixed bacterial/yeast olive fermentations are only recently being explored. Of all the metabolites lactic acid is the most important as it acts as a natural preservative lowering the pH of the solution to make the final product more stable against the growth of unwanted pathogenic species. The result is table olives which will store with or without refrigeration, and thus lactic acid bacteria dominated fermentations are generally considered the most suitable method of curing olives. Yeast dominated fermentations produce a different suite of metabolites which have less self-preservation characteristics and therefore acid corrected, often with citric acid, in the final processing stage to achieve microbial stability.

There are many types of preparations for table olives depending on local tastes and traditions. The most important commercial examples are:

Spanish or Sevillian type (Olives with fermentation). Most commonly applied to green olive preparation. Around 60% of all the worlds table olives are produced with this method. Olives are soaked in lye (Dilute NaOH, 2-4%) for 8–10 hours to hydrolyse the oleuropein. They are usually considered "treated" when the lye has penetrated two-thirds of the way into the fruit. 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. The brine is changed on a regular basis to help remove the phenolic compounds. Fermentation is carried out by the natural microbiota present on the olives that survive the lye treatment process. Many organisms are involved, usually reflecting the local conditions or "Terroir" of the olives. During a typical fermentation gram-negative enterobacteria flourish in small numbers at first, but are rapidly outgrown by Lactic acid bacteria species such as Leuconostoc mesenteroides, Lactobacillus plantarum, Lactobacillus brevis and Pediococcus damnosus. These bacteria produce lactic acid to help lower the acidity of the brine and therefore stabilize the product against unwanted pathogenic species. A diversity of yeasts then accumulate in sufficient numbers to help complete the fermentation alongside the lactic acid bacteria. Yeast commonly mentioned include the teleomorphs Pichia anomala, Pichia membranifaciens, Debaryomyces hansenii and Kluyveromyces marxianus. Once fermented, the olives are placed in fresh brine and acid corrected ready for market.

Sicilian or Greek type. (Olives with fermentation). Applied to green, semi-ripe and ripe olives. Almost identical the Spanish type fermentation process, however the lye treatment process is skipped and the olives are placed directly in fermentation vessels full of brine (8-12% NaCl). The brine is changed on a regular basis to help remove the phenolic compounds. As the caustic treatment is avoided, Lactic acid bacteria are only present in similar numbers to yeast and appear to be outcompeted by the abundant yeasts found on untreated olives. As there is very little acid produced by the yeast fermentation, lactic, acetic, or citric acid is often added to the fermentation stage to stabilize the process.

Picholine or directly-brined type. (Olives with fermentation). Can be applied to green, semi-ripe or ripe preparations. Olives are soaked in lye typically for longer periods than Spanish style (e.g. 10–72 hours) until the solution has penetrated three-quarters of the way into the fruit. They are then washed and immediately brined and acid corrected with citric acid to achieve microbial stability. Fermentation still occurs carried out by acidogenic yeast and bacteria, but is more subdued than other methods. The brine is changed on a regular basis to help remove the phenolic compounds and a series of progressively stronger concentrations of NaCl are added until the product is fully stabilized and ready to be eaten.

Water-cured type. (Olives with fermentation). Can be applied to green, semi-ripe or ripe preparations. Olives are soaked in water or weak brine and this solution is changed on a daily basis for 10–14 days. The oleuropein in naturally dissolved and leached into the water and removed during a continual soak-wash cycle. Fermentation takes place during the water treatment stage and involves a mixed yeast/bacteria ecosystem. Sometimes, the olives are lightly cracked with a hammer or a stone to trigger fermentation and speed up the fermentation process. Once debittered the olives are brined to concentrations of 8-12% NaCl, acid corrected and ready to eat.

Salt-cured type. (Olives with minor fermentation). Applied only to ripe olives and usually produced in Morocco or Turkey and other eastern Mediterranean countries. Once picked, the olives are vigorously washed and packed in alternating layers with salt. The high concentrations of salt draw the moisture out of olives, dehydrating and shrivelling them until they look somewhat analogous to a raisin. Once packed in salt, fermentation is minimal and only initiated by the most halophilic yeast species such as Debaryomyces hansenii. Once cured, they are sold in their natural state without any additives.

California or "artificial ripening" type. (Olives without fermentation). Applied to green and semi-ripe olives. Olives are placed in lye and soaked. Upon their removal they are washed in water injected with compressed air. This process is repeated several times until both oxygen and lye have soaked through to the pit. The repeated, saturated exposure to air oxidises the skin and flesh of the fruit, turning it black in an artificial process that mimics natural ripening. Once fully oxidised or "blackened", they are brined and acid corrected ready for eating.

Olive wood
Olive wood is very hard and is prized for its durability, colour, high combustion temperature and interesting grain patterns. Because of the commercial importance of the fruit, and the relatively small size of the tree, olive wood and its products are relatively expensive. Common uses of the wood include: kitchen utensils, carved wooden bowls, cutting boards, fine furniture, and decorative items.

Olive tree parts, and olive oil, have a number of common phenolic compounds that might possess positive health effect to the human body, as well as a good source of vitamin E. The processing of olives (fruit) especially affects their phenolic content, but other parts of the plant also contain phenolics, such as leaves and bark.

The addition of iron salts such as Iron(II) gluconate, as commonly in canned olives, drastically reduces phenolic content, especially hydroxytyrosol. Total polyphenol contents, as measured by the Folin method, are 117 mg/100 g in black olives and 161 mg/100 g in green olives, as compared to 55 and 21 mg/100 g for extra virgin and virgin olive oil respectively. Olive fruit contain several types of polyphenols, mainly tyrosols, phenolic acids, flavonols and flavones, and for black olives, anthocyanins. During the crushing, kneading and extraction of olive fruit to obtain olive oil, the glycosidic oleuropein, demethyloleuropein and ligstroside are hydrolyzed by endogenous Beta-glucosidases, to form aldehydic aglycones. The aglycones become soluble in the oil phase, whereas the glycosides remain in the water phase; fresh cloudy olive oil has the added benefit of containing these water phase phenolics. Lignans are also found in olive fruit and oils.

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