Olive oil



Olive oil is a liquid obtained from olives (the fruit of Olea europaea; family Oleaceae), a traditional tree crop of the Mediterranean Basin. The oil is produced by pressing whole olives. It is commonly used in cooking, whether for frying or as a salad dressing. It is also used in cosmetics, pharmaceuticals, and soaps, and as a fuel for traditional oil lamps, and has additional uses in some religions. There is limited evidence of its possible health benefits. The olive is one of three core food plants in Mediterranean cuisine; the other two are wheat and grapes. Olive trees have been grown around the Mediterranean since the 8th millennium BC.

Today, Spain is the largest producer of olive oil by volume, followed by Italy and Greece. However, per capita national consumption is highest in Greece, followed by Spain, Italy, and Tunisia. Consumption in South Asia, North America and northern Europe is far less, but rising steadily.

The composition of olive oil varies with the cultivar, altitude, time of harvest and extraction process. It 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.

Early cultivation


The olive tree is native to the Mediterranean basin; wild olives were collected by Neolithic people as early as the 8th millennium BC. The wild olive tree originated in Asia Minor or in ancient Greece. It is not clear when and where olive trees were first domesticated: in Asia Minor, in the Levant, or somewhere in the Mesopotamian part of the Fertile Crescent.

Archaeological evidence shows that olives were turned into olive oil by 6000 BC and 4500 BC at a now-submerged prehistoric settlement south of Haifa. Until 1500 BC, eastern coastal areas of the Mediterranean were most heavily cultivated. Evidence also suggests that olives were being grown in Crete as long ago as 2500 BC. The earliest surviving olive oil amphorae date to 3500 BC (Early Minoan times), though the production of olive oil is assumed to have started before 4000 BC. Olive trees were certainly cultivated by the Late Minoan period (1500 BC) in Crete, and perhaps as early as the Early Minoan. The cultivation of olive trees in Crete became particularly intense in the post-palatial period and played an important role in the island's economy, as it did across the Mediterranean.

Recent genetic studies suggest that species used by modern cultivators descend from multiple wild populations, but a detailed history of domestication is not yet forthcoming.

History and trade


Olive trees and oil production in the Eastern Mediterranean can be traced to archives of the ancient city-state Ebla (2600–2240 BC), which were located on the outskirts of the Syrian city Aleppo. Here some dozen documents dated 2400 BC describe lands of the king and the queen. These belonged to a library of clay tablets perfectly preserved by having been baked in the fire that destroyed the palace. A later source is the frequent mentions of oil in the Tanakh. Dynastic Egyptians before 2000 BC imported olive oil from Crete, Syria and Canaan and oil was an important item of commerce and wealth. Remains of olive oil have been found in jugs over 4,000 years old in a tomb on the island of Naxos in the Aegean Sea. Sinuhe, the Egyptian exile who lived in northern Canaan about 1960 BC, wrote of abundant olive trees.

Besides food, olive oil has been used for religious rituals, medicines, as a fuel in oil lamps, soap-making, and skin care application. The Minoans used olive oil in religious ceremonies. The oil became a principal product of the Minoan civilization, where it is thought to have represented wealth. Olive oil, a multi-purpose product of Mycenaean Greece (c. 1600–1100 BC) at that time, was a chief export. Olive tree growing reached Iberia and Etruscan cities well before the 8th century BC through trade with the Phoenicians and Carthage, then was spread into Southern Gaul by the Celtic tribes during the 7th century BC. Over 100 olive presses have been found in Tel Miqne (Ekron), one of the five main cities of the Biblical Philistines. These presses are estimated to have had output of between 1,000 and 3,000 tons of olive oil per season.

Many ancient presses still exist in the Eastern Mediterranean region, and some dating to the Roman period are still in use today.

Olive oil was common in ancient Greek and Roman cuisine. According to Herodotus, Apollodorus, Plutarch, Pausanias, Ovid and other sources, the city of Athens obtained its name because Athenians considered olive oil essential, preferring the offering of the goddess Athena (an olive tree) over the offering of Poseidon (a spring of salt water gushing out of a cliff). The Spartans and other Greeks used oil to rub themselves while exercising in the gymnasia. From its beginnings early in the 7th century BC, the cosmetic use of olive oil quickly spread to all of the Hellenic city states, together with athletes training in the nude, and lasted close to a thousand years despite its great expense. Olive oil was also popular as a form of birth control; Aristotle in his History of Animals recommends applying a mixture of olive oil combined with either oil of cedar, ointment of lead, or ointment of frankincense to the cervix to prevent pregnancy. Olive trees were planted throughout the entire Mediterranean basin during evolution of the Roman Republic and Empire. According to the historian Pliny the Elder, Italy had "excellent olive oil at reasonable prices" by the 1st century AD—"the best in the Mediterranean", he maintained.



The importance and antiquity of olive oil can be seen in the fact that the English word oil derives from c. 1175, olive oil, from Anglo-Fr. and O.N.Fr. olie, from O.Fr. oile (12c., Mod.Fr. huile), from L. oleum "oil, olive oil" (cf. It. olio), from Gk. elaion "olive tree", which may have been borrowed through trade networks from the Semitic Phoenician use of el'yon meaning "superior", probably in recognized comparison to other vegetable or animal fats available at the time. Robin Lane Fox suggests that the Latin borrowing of Greek elaion for oil (Latin oleum) is itself a marker for improved Greek varieties of oil-producing olive, already present in Italy as Latin was forming, brought by Euboean traders, whose presence in Latium is signaled by remains of their characteristic pottery, from the mid-8th century.

Varieties
There are many olive cultivars, each with a particular flavor, texture, and shelf life that make them more or less suitable for different applications, such as direct human consumption on bread or in salads, indirect consumption in domestic cooking or catering, or industrial uses such as animal feed or engineering applications. During the stages of maturity, olive fruit changes color from green to violet, and then black. Olive oil taste characteristics depend on which stage of ripeness olive fruits are collected.

Culinary use
Olive oil is an important cooking oil in countries surrounding the Mediterranean, and it forms one of the three staple food plants of Mediterranean cuisine, the other two being wheat (as in pasta, bread, and couscous) and the grape, used as a dessert fruit and for wine.

Extra virgin olive oil is mostly used as a salad dressing and as an ingredient in salad dressings. It is also used with foods to be eaten cold. If uncompromised by heat, the flavor is stronger. It also can be used for sautéing.

When extra virgin olive oil is heated above 210 - 216 C, depending on its free fatty acid content, the unrefined particles within the oil are burned. This leads to deteriorated taste. Also, most consumers do not like the pronounced taste of extra virgin olive oil for deep fried foods. Refined olive oils are suited for deep frying because of the higher smoke point and milder flavour. Extra virgin oils have a smoke point around 180–215 °C (356–419 °F) whereas refined light olive oil has a smoke point up to 230 °C (446 °F). "Contrary to popular myths, high quality EVOO [extra virgin olive oil] is an excellent choice for cooking. High quality EVOO has a smoke point well above the standard temperatures required for cooking, and its resistance to oxidation is higher than most cooking oils due to the antioxidant and mono-unsaturated fat content." "The smoke point of a good extra-virgin olive oil is 210 °C (420 °F). The smoke point is higher in good extra-virgin olive oil and lower in low-quality virgin olive oil."

Choosing a cold-pressed olive oil can be similar to selecting a wine. The flavor of these oils varies considerably and a particular oil may be more suited for a particular dish.

Fresh oil, as available in an oil-producing region, tastes noticeably different from the older oils available elsewhere. In time, oils deteriorate and become stale. One-year-old oil may be still pleasant to the taste, but it is less fragrant than fresh oil. After the first year, olive oil is more suitable for cooking than serving raw.

The taste of the olive oil is influenced by the varietals used to produce the oil and by the moment when the olives are harvested and ground (less ripe olives give more bitter and spicy flavors – riper olives give a sweeter sensation in the oil).

Christianity
The Roman Catholic, Orthodox and Anglican churches use olive oil for the Oil of Catechumens (used to bless and strengthen those preparing for Baptism) and Oil of the Sick (used to confer the Sacrament of Anointing of the Sick or Unction). Olive oil mixed with a perfuming agent such as balsam is consecrated by bishops as Sacred Chrism, which is used to confer the sacrament of Confirmation (as a symbol of the strengthening of the Holy Spirit), in the rites of Baptism and the ordination of priests and bishops, in the consecration of altars and churches, and, traditionally, in the anointing of monarchs at their coronation.

Eastern Orthodox Christians still use oil lamps in their churches, home prayer corners and in the cemeteries. A vigil lamp consists of a votive glass containing a half-inch of water and filled the rest with olive oil. The glass has a metal holder that hangs from a bracket on the wall or sits on a table. A cork float with a lit wick floats on the oil. To douse the flame, the float is carefully pressed down into the oil. Makeshift oil lamps can easily be made by soaking a ball of cotton in olive oil and forming it into a peak. The peak is lit and then burns until all the oil is consumed, whereupon the rest of the cotton burns out. Olive oil is a usual offering to churches and cemeteries.

The Church of Jesus Christ of Latter-day Saints uses virgin olive oil that has been blessed by the priesthood. This consecrated oil is used for anointing the sick.

Judaism
In Jewish observance, olive oil was the only fuel allowed to be used in the seven-branched menorah in the Mishkan service during the Exodus of the tribes of Israel from Egypt, and later in the permanent Temple in Jerusalem. It was obtained by using only the first drop from a squeezed olive and was consecrated for use only in the Temple by the priests and stored in special containers. Although candles can be used to light the menorah at Hanukkah, oil containers are preferred, to imitate the original menorah. Another use of oil in Jewish religion was for anointing the kings of the Kingdom of Israel, originating from King David. Tzidkiyahu was the last anointed King of Israel.

Skin care
Olive oil has a long history of being used as a home skincare remedy. Egyptians used it alongside beeswax as a cleanser, moisturizer, and antibacterial agent since pharaonic times. In ancient Greece, olive oil was used during massage, to prevent sports injuries and relieve muscle fatigue. In 2000, Japan was the top importer of olive oil in Asia (13,000 tons annually) because consumers there believe both the ingestion and topical application of olive oil to be good for skin and health.

Olive oil is popular for use in massaging infants and toddlers, but scientific evidence of its efficacy is mixed. One analysis of olive oil versus mineral oil found that, when used for infant massage, olive oil can be considered a safe alternative to sunflower, grapeseed and fractionated coconut oils. This stands true particularly when it is mixed with a lighter oil like sunflower, which "would have the further effect of reducing the already low levels of free fatty acids present in olive oil". Another trial stated that olive oil lowered the risk of dermatitis for infants in all gestational stages when compared with emollient cream. However, yet another study on adults found that topical treatment with olive oil "significantly damages the skin barrier" when compared to sunflower oil, and that it may make existing atopic dermatitis worse. The researchers concluded that due to the negative outcome in adults, they do not recommend the use of olive oil for the treatment of dry skin and infant massage.

Applying olive oil to the skin does not help prevent or reduce stretch marks.

Other
Olive oil is also a natural and safe lubricant, and can be used to lubricate kitchen machinery (grinders, blenders, cookware, etc.). It can also be used for illumination (oil lamps) or as the base for soaps and detergents. Some cosmetics also use olive oil as their base, and it can be used as a substitute for machine oil. Olive oil has also been used as both solvent and ligand in the synthesis of cadmium selenide quantum dots.

Extraction


Olive oil is produced by grinding olives and extracting the oil by mechanical or chemical means. Green olives usually produce more bitter oil, and overripe olives can produce oil that is rancid, so for good extra virgin olive oil care is taken to make sure the olives are perfectly ripened. The process is generally as follows:

The oil produced by only physical (mechanical) means as described above is called virgin oil. Extra virgin olive oil is virgin olive oil that satisfies specific high chemical and organoleptic criteria (low free acidity, no or very little organoleptic defects). A higher grade extra virgin olive oil is mostly dependent on favourable weather conditions; a drought during the flowering phase, for example, can result in a lower quality (virgin) oil. It is worth noting that olive trees produce well every couple of years, so greater harvests occur in alternate years (the year in-between is when the tree yields less). However the quality is still dependent on the weather.
 * 1) The olives are ground into paste using large millstones (traditional method) or steel drums (modern method).
 * 2) If ground with mill stones, the olive paste generally stays under the stones for 30 to 40 minutes. A shorter grinding process may result in a more raw paste that produces less oil and has a less ripe taste, a longer process may increase oxidation of the paste and reduce the flavor. After grinding, the olive paste is spread on fiber disks, which are stacked on top of each other in a column, then placed into the press. Pressure is then applied onto the column to separate the vegetal liquid from the paste. This liquid still contains a significant amount of water. Traditionally the oil was shed from the water by gravity (oil is less dense than water). This very slow separation process has been replaced by centrifugation, which is much faster and more thorough. The centrifuges have one exit for the (heavier) watery part and one for the oil. Olive oil should not contain significant traces of vegetal water as this accelerates the process of organic degeneration by microorganisms. The separation in smaller oil mills is not always perfect, thus sometimes a small watery deposit containing organic particles can be found at the bottom of oil bottles.
 * 3) In modern steel drum mills the grinding process takes about 20 minutes. After grinding, the paste is stirred slowly for another 20 to 30 minutes in a particular container (malaxation), where the microscopic oil drops aggregate into bigger drops, which facilitates the mechanical extraction. The paste is then pressed by centrifugation/ the water is thereafter separated from the oil in a second centrifugation as described before.
 * 1) Sometimes the produced oil will be filtered to eliminate remaining solid particles that may reduce the shelf life of the product. Labels may indicate the fact that the oil has not been filtered, suggesting a different taste. Fresh unfiltered olive oil usually has a slightly cloudy appearance, and is therefore sometimes called cloudy olive oil. This form of olive oil used to be popular only among olive oil small scale producers but is now becoming "trendy", in line with consumer's demand for products that are perceived to be less processed. But generally, if not tasted or consumed soon after production, filtered olive oil should be preferred: "Some producers maintain that extra-virgin olive oils do not need filtration but also that filtration is detrimental to oil quality. This point of view should be considered as erroneous and probably the result of improper implementation of this operation. In fact, fine particles that are suspended in a virgin olive oil, even after the most effective centrifugal finishing, contain water and enzymes that may impair oil stability and ruin its sensory profile. [...] Filtration makes an extra-virgin olive oil more stable and also more attractive. If the suspended particles are not removed they slowly agglomerate and flocculate, forming a deposit on the bottom of the storage containers. Such a deposit continues to be at risk of enzymatic spoilage and, in the worst case, of development of anaerobic micro-organisms with further spoilage and hygienic risk. [...] It is [...] recommended that filtration be carried out as soon as possible after centrifugal separation and finishing."

Pomace handling
The remaining semi-solid waste, called pomace, retains a small quantity (about 5–10%) of oil that cannot be extracted by further pressing, but only with chemical solvents. This is done in specialized chemical plants, not in the oil mills. The resulting oil is not "virgin" but "pomace oil".

Handling of olive waste is an environmental challenge because the wastewater, which amounts to millions of tons (billions of liters) annually in the European Union, is not biodegradable, is toxic to plants, and cannot be processed through conventional water treatment systems. Traditionally, olive pomace would be used as compost or developed as a possible biofuel, although these uses introduce concern due to chemicals present in the pomace. A process called "valorization" of olive pomace is under research and development, consisting of additional processing to obtain value-added byproducts, such as animal feed, food additives for human products, and phenolic and fatty acid extracts for potential human use.

Production


In 2016/17 period, world production of virgin olive oil was 2.586,5 thousand tonnes (table), an 18,6% decrease under 2015/16 global production. Spain produced 1.290,6 thousand tonnes or 50% of world production. The next six largest producers – Greece, Italy, Turkey, Morocco, Syria and Tunisia – collectively produced 70 percent of Spain's annual total (table).

In the EU, Eurostat reported in 2007 that there were 1.9 million farms with olive groves. The olive sector is characterised by a large number of small operations. The largest holdings are in Andalucía (8 ha/holding on average) in Spain and Alentejo (7.5 ha/holding) in Portugal while the smallest are located in Cyprus (0.5 ha/holding), Apulia and Crete (1.7 ha/holding).

Some 75% of Spain's production derives from the region of Andalucía, particularly within Jaén province which produces 70% of olive oil in Spain. The world's largest olive oil mill (almazara, in Spanish), capable of processing 2,500 tonnes of olives per day, is in the town of Villacarrillo, Jaén.

In 2016/2017 Greece was the second largest producer of olive oil with 195,000 tons produced. As of 2009, there were 531,000 farms cultivating 730,000 ha from 132 million trees producing 310–350,000 tons of olive oil.

Italy produced 182,300 tonnes in 2016/17 or 7,6% of the world's production (table). Even though the production can change from year to year, usually major Italian producers are the regions of Calabria and, above all, Apulia. Many PDO and PGI extra-virgin olive oil are produced in these regions. In Apulia, among the villages of Carovigno, Ostuni and Fasano is the Plain of Olive Trees, which counts some specimens as old as 3000 years; it has been proposed add this plain to the UNESCO Heritage List. Excellent extra-virgin olive oil is also produced in Tuscany, in cities like Lucca, Florence, Siena which are also included in the association of "Città dell'Olio". Italy imports about 65% of Spanish olive oil exports. Some Italian companies are known to mix the imported olive oil with alternate oils (such as soy) and falsely market the blend as authentic olive oil "Made in Italy",  creating a fraud that the European Commission has attempted to overcome by offering a 5 million Euro reward to stimulate better methods of authentication.

Turkey is the largest producer outside the EU (table), with 178,000 tons produced in 2016/2017, cultivating from 174.594 thousand trees.

Tunisia is the fourth largest producer outside the EU (table), with 100,000 tons produced in 2016 to 2017, among which 73% was exported to Europe. Because of the arid climate, pesticides and herbicides are largely unnecessary in Tunisia.

While the majority (between 60–70%) of olive oil consumed in Australia is imported from Europe, a smaller domestic industry does exist. Many Australian producers only make premium small-batch oils, while a number of corporate growers operate groves of a million trees or more and produce oils for the general market. 11% of Australian production is exported, mostly to Asia.

In North America, Italian and Spanish olive oils are the best-known, and top-quality extra virgin olive oil from Italy, Spain, Portugal and Greece are sold at high prices, often in prestige packaging. A large part of U.S. olive oil imports come from Italy, Spain, and Turkey.

The United States produces olive oil in California, Hawaii, Texas, Georgia, and Oregon.

Global consumption
Greece has by far the largest per capita consumption of olive oil worldwide, over 24 l per person per year; Spain and Italy, around 14 l; Tunisia, Portugal, Syria, Jordan and Lebanon, around 8 l. Northern Europe and North America consume far less, around 0.7 l, but the consumption of olive oil outside its home territory has been rising steadily.

Regulation
The International Olive Council (IOC) is an intergovernmental organisation of states that produce olives or products derived from olives, such as olive oil. The IOC officially governs 95% of international production and holds great influence over the rest. The EU regulates the use of different protected designation of origin labels for olive oils.

The United States is not a member of the IOC and is not subject to its authority, but on October 25, 2010, the U.S. Department of Agriculture adopted new voluntary olive oil grading standards that closely parallel those of the IOC, with some adjustments for the characteristics of olives grown in the U.S. Additionally, U.S. Customs regulations on "country of origin" state that if a non-origin nation is shown on the label, then the real origin must be shown on the same side of the label and in comparable size letters so as not to mislead the consumer. Yet most major U.S. brands continue to put "imported from Italy" on the front label in large letters and other origins on the back in very small print. "In fact, olive oil labeled 'Italian' often comes from Turkey, Tunisia, Morocco, Spain, and Greece." This makes it unclear what percentage of the olive oil is really of Italian origin.

Commercial grades


All production begins by transforming the olive fruit into olive paste by crushing or pressing. This paste is then malaxed (slowly churned or mixed) to allow the microscopic oil droplets to agglomerate. The oil is then separated from the watery matter and fruit pulp with the use of a press (traditional method) or centrifugation (modern method). After extraction the remnant solid substance, called pomace, still contains a small quantity of oil.

To classify its organoleptic qualities, olive oil is judged by a panel of trained tasters in a blind taste test.

One parameter used to characterise an oil is its acidity. In this context, "acidity" is not chemical acidity in the sense of pH, but the percent (measured by weight) of free oleic acid. Measured by quantitative analysis, acidity is a measure of the hydrolysis of the oil's triglycerides: as the oil degrades, more fatty acids are freed from the glycerides, increasing the level of free acidity and thereby increasing hydrolytic rancidity. Another measure of the oil's chemical degradation is the peroxide value, which measures the degree to which the oil is oxidized by free radicals, leading to oxidative rancidity. Phenolic acids present in olive oil also add acidic sensory properties to aroma and flavor.

The grades of oil extracted from the olive fruit can be classified as:
 * Virgin means the oil was produced by the use of mechanical means only, with no chemical treatment. The term virgin oil with reference to production method includes all grades of virgin olive oil, including Extra virgin, Virgin, Ordinary virgin and Lampante virgin olive oil products, depending on quality (see below).
 * Lampante virgin oil is olive oil extracted by virgin (mechanical) methods but not suitable for human consumption without further refining; “lampante” is the attributive form of “lampa”, the Italian word for “lamp”, referring to the earlier use of such oil in oil lamps. Lampante virgin oil can be used for industrial purposes, or refined (see below) to make it edible.
 * Refined olive oil is the olive oil obtained from any grade of virgin olive oil by refining methods which do not lead to alterations in the initial glyceridic structure. The refining process removes colour, odour and flavour from the olive oil, and leaves behind a very pure form of olive oil that is tasteless, colourless and odourless and extremely low in free fatty acids. Olive oils sold as the grades Extra virgin olive oil and Virgin olive oil therefore cannot contain any refined oil.
 * Crude olive pomace oil is the oil obtained by treating olive pomace (the leftover paste after the pressing of olives for virgin olive oils) with solvents or other physical treatments, to the exclusion of oils obtained by re-esterification processes and of any mixture with oils of other kinds. It is then further refined into Refined olive pomace oil and once re-blended with virgin olive oils for taste, is then known as Olive pomace oil.



International Olive Council
In countries that adhere to the standards of the International Olive Council, as well as in Australia, and under the voluntary United States Department of Agriculture labeling standards in the United States:

Extra virgin olive oil is the highest grade of virgin oil derived by cold mechanical extraction without use of solvents or refining methods. It contains no more than 0.8% free acidity, and is judged to have a superior taste, having some fruitiness and no defined sensory defects. Extra virgin olive oil accounts for less than 10% of oil in many producing countries; the percentage is far higher in the Mediterranean countries (Greece: 80%, Italy: 65%, Spain 50%).

Virgin olive oil is a lesser grade of virgin oil, with free acidity of up to 2.0%, and is judged to have a good taste, but may include some sensory defects.

Refined olive oil is virgin oil that has been refined using charcoal and other chemical and physical filters, methods which do not alter the glyceridic structure. It has a free acidity, expressed as oleic acid, of not more than 0.3 grams per 100 grams (0.3%) and its other characteristics correspond to those fixed for this category in this standard. It is obtained by refining virgin oils to eliminate high acidity or organoleptic defects. Oils labeled as Pure olive oil or Olive oil are primarily refined olive oil, with a small addition of virgin for taste.

Olive pomace oil is refined pomace olive oil, often blended with some virgin oil. It is fit for consumption, but may not be described simply as olive oil. It has a more neutral flavor than pure or virgin olive oil, making it unfashionable among connoisseurs; however, it has the same fat composition as regular olive oil, giving it the same health benefits. It also has a high smoke point, and thus is widely used in restaurants as well as home cooking in some countries.

United States
As the United States is not a member, the IOC retail grades have no legal meaning there, but on October 25, 2010, the United States Department of Agriculture (USDA) established Standards for Grades of Olive Oil and Olive-Pomace Oil, which closely parallel the IOC standards:
 * U.S. Extra Virgin Olive Oil for oil with excellent flavor and odor and free fatty acid content of not more than 0.8 g per 100 g (0.8%);
 * U.S. Virgin Olive Oil for oil with reasonably good flavor and odor and free fatty acid content of not more than 2 g per 100 g (2%);
 * U.S. Virgin Olive Oil Not Fit For Human Consumption Without Further Processing is a virgin (mechanically-extracted) olive oil of poor flavor and odor, equivalent to the IOC's lampante oil;
 * U.S. Olive Oil is a mixture of virgin and refined oils;
 * U.S. Refined Olive Oil is an oil made from refined oils with some restrictions on the processing.

These grades are voluntary. Certification is available, for a fee, from the USDA.

Several olive producer associations, such as the North American Olive Oil Association and the California Olive Oil Council, also offer grading and certification within the United States. Oleologist Nicholas Coleman suggests that the California Olive Oil Council certification is the most stringent of the voluntary grading schemes in the United States.

Label wording
Furthermore, there is no "second" press of virgin oil, so the term "first press" means only that the oil was produced in a press vs. other possible methods.
 * Different names for olive oil indicate the degree of processing the oil has undergone as well as the quality of the oil. Extra virgin olive oil is the highest grade available, followed by virgin olive oil. The word "virgin" indicates that the olives have been pressed to extract the oil; no heat or chemicals have been used during the extraction process, and the oil is pure and unrefined. Virgin olive oils contain the highest levels of polyphenols, antioxidants that have been linked with better health.
 * Olive Oil, which is sometimes denoted as being "Made from refined and virgin olive oils" is a blend of refined olive oil with a virgin grade of olive oil. Pure, Classic, Light and Extra-Light are terms introduced by manufacturers in countries that are non-traditional consumers of olive oil for these products to indicate both their composition of being only 100% olive oil, and also the varying strength of taste to consumers.  Contrary to a common consumer belief, they do not have fewer calories than extra virgin oil as implied by the names.
 * Cold pressed or Cold extraction means "that the oil was not heated over a certain temperature (usually 27 C) during processing, thus retaining more nutrients and undergoing less degradation". The difference between Cold Extraction and Cold Pressed is regulated in Europe, where the use of a centrifuge, the modern method of extraction for large quantities, must be labelled as Cold Extracted, while only a physically pressed olive oil may be labelled as Cold Pressed.  In many parts of the world, such as Australia, producers using centrifugal extraction still label their products as Cold Pressed.
 * First cold pressed means "that the fruit of the olive was crushed exactly one time – i.e., the first press. The cold refers to the temperature range of the fruit at the time it is crushed". In Calabria (Italy) the olives are collected in October. In regions like Tuscany or Liguria, the olives collected in November and ground, often at night, are too cold to be processed efficiently without heating. The paste is regularly heated above the environmental temperatures, which may be as low as 10–15 °C, to extract the oil efficiently with only physical means. Olives pressed in warm regions like Southern Italy or Northern Africa may be pressed at significantly higher temperatures although not heated. While it is important that the pressing temperatures be as low as possible (generally below 25 °C) there is no international reliable definition of "cold pressed".
 * Protected designation of origin (PDO) and protected geographical indication (PGI) refer to olive oils with "exceptional properties and quality derived from their place of origin as well as from the way of their production".
 * The label may indicate that the oil was bottled or packed in a stated country. This does not necessarily mean that the oil was produced there. The origin of the oil may sometimes be marked elsewhere on the label; it may be a mixture of oils from more than one country.
 * The U.S. Food and Drug Administration permitted a claim on olive oil labels stating: "Limited and not conclusive scientific evidence suggests that eating about two tablespoons (23 g) of olive oil daily may reduce the risk of coronary heart disease."

Adulteration
There have been allegations, particularly in Italy and Spain, that regulation can be sometimes lax and corrupt. Major shippers are claimed to routinely adulterate olive oil so that only about 40% of olive oil sold as "extra virgin" in Italy actually meets the specification. In some cases, colza oil (extracted from rapeseed) with added color and flavor has been labeled and sold as olive oil. This extensive fraud prompted the Italian government to mandate a new labeling law in 2007 for companies selling olive oil, under which every bottle of Italian olive oil would have to declare the farm and press on which it was produced, as well as display a precise breakdown of the oils used, for blended oils. In February 2008, however, EU officials took issue with the new law, stating that under EU rules such labeling should be voluntary rather than compulsory. Under EU rules, olive oil may be sold as Italian even if it only contains a small amount of Italian oil.

Extra virgin olive oil has strict requirements and is checked for "sensory defects" that include: rancid, fusty, musty, winey (vinegary) and muddy sediment. These defects can occur for different reasons. The most common are:
 * Raw material (olives) infected or battered
 * Inadequate harvest, with contact between the olives and soil

In March 2008, 400 Italian police officers conducted "Operation Golden Oil", arresting 23 people and confiscating 85 farms after an investigation revealed a large-scale scheme to relabel oils from other Mediterranean nations as Italian. In April 2008, another operation impounded seven olive oil plants and arrested 40 people in nine provinces of northern and southern Italy for adding chlorophyll to sunflower and soybean oil, and selling it as extra virgin olive oil, both in Italy and abroad; 25,000 liters of the fake oil were seized and prevented from being exported.

On March 15, 2011, the prosecutor's office in Florence, Italy, working in conjunction with the forestry department, indicted two managers and an officer of Carapelli, one of the brands of the Spanish company Grupo SOS (which recently changed its name to Deoleo). The charges involved falsified documents and food fraud. Carapelli lawyer Neri Pinucci said the company was not worried about the charges and that "the case is based on an irregularity in the documents."

In February 2012, an international olive oil scam was alleged by Spanish police to have taken place, in which palm, avocado, sunflower and other cheaper oils were passed off as Italian olive oil. Police said the oils were blended in an industrial biodiesel plant and adulterated in a way to hide markers that would have revealed their true nature. The oils were not toxic and posed no health risk, according to a statement by the Guardia Civil. Nineteen people were arrested following the year-long joint probe by the police and Spanish tax authorities, part of what they call Operation Lucerna.

Using tiny print to state the origin of blended oil is used as a legal loophole by manufacturers of adulterated and mixed olive oil.

Journalist Tom Mueller has investigated crime and adulteration in the olive oil business, publishing the article "Slippery Business" in New Yorker magazine, followed by the 2011 book Extra Virginity. On 3 January 2016 Bill Whitaker presented a program on CBS News including interviews with Mueller and with Italian authorities. It was reported that in the previous month 5,000 tons of adulterated olive oil had been sold in Italy, and that organised crime was heavily involved—the term "Agrimafia" was used. The point was made by Mueller that the profit margin on adulterated olive oil was three times that on the illegal narcotic drug cocaine. He said that over 50% of olive oil sold in Italy was adulterated, as was 75–80% of that sold in the US. Whitaker reported that 3 samples of "extra virgin olive oil" had been bought in a US supermarket and tested; two of the three samples did not meet the required standard, and one of them—with a top-selling US brand—was exceptionally poor. Similar analyses conducted in 2011 found that 73% of the top-selling "extra virgin olive oil" brands in California supermarkets failed to meet the sensory qualifications for true extra virgin oils.

In early February 2017, the Carabinieri arrested 33 suspects in the Calabrian mafia's Piromalli 'ndrina ('Ndrangheta) which was allegedly exporting fake extra virgin olive oil to the U.S.; the product was actually inexpensive olive pomace oil fraudulently labeled. Less than a year earlier, the American television program 60 Minutes had warned that "the olive oil business has been corrupted by the Mafia" and that "Agromafia" was a $16-billion per year enterprise. A Carabinieri investigator interviewed on the program said that "olive oil fraud has gone on for the better part of four millennia" but today, it's particularly "easy for the bad guys to either introduce adulterated olive oils or mix in lower quality olive oils with extra-virgin olive oil". Weeks later, a report by Forbes stated that "it's reliably reported that 80% of the Italian olive oil on the market is fraudulent" and that "a massive olive oil scandal is being uncovered in Southern Italy (Puglia, Umbria and Campania)".

Constituents


Olive oil is composed mainly of the mixed triglyceride esters of oleic acid, linoleic acid, palmitic acid and of other fatty acids, along with traces of squalene (up to 0.7%) and sterols (about 0.2% phytosterol and tocosterols). The composition varies by cultivar, region, altitude, time of harvest, and extraction process.

Phenolic composition
Olive oil contains traces of phenolics (about 0.5%), such as esters of tyrosol, hydroxytyrosol, oleocanthal and oleuropein, which give extra virgin olive oil its bitter, pungent taste, and are also implicated in its aroma. Olive oil is a source of at least 30 phenolic compounds, among which are elenolic acid, a marker for maturation of olives, and alpha-tocopherol, one of the eight members of the Vitamin E family. Oleuropein, together with other closely related compounds such as 10-hydroxyoleuropein, ligstroside and 10-hydroxyligstroside, are tyrosol esters of elenolic acid.

Other phenolic constituents include flavonoids, lignans and pinoresinol.

Nutrition
One tablespoon of olive oil (13.5 g) contains the following nutritional information according to the USDA:
 * Calories: 119
 * Fat: 13.5 g (21% of the Daily Value, DV)
 * Saturated fat: 2 g (9% of DV)
 * Carbohydrates: 0
 * Fibers: 0
 * Protein: 0
 * Vitamin E: 1.9 mg (10% of DV)
 * Vitamin K: 8.1 µg (10% of DV)

Potential health effects
In the United States, the FDA allows producers of olive oil to place the following qualified health claim on product labels:

In a review by the European Food Safety Authority (EFSA) in 2011, health claims on olive oil were approved for protection by its polyphenols against oxidation of blood lipids, and for maintenance of normal blood LDL-cholesterol levels by replacing saturated fats in the diet with oleic acid. (Commission Regulation (EU) 432/2012 of 16 May 2012). Despite its approval, the EFSA has noted that a definitive cause-and-effect relationship has not been adequately established for consumption of olive oil and maintaining normal (fasting) blood concentrations of triglycerides, normal blood HDL-cholesterol concentrations, and normal blood glucose concentrations.

A 2014 meta-analysis concluded that increased consumption of olive oil was associated with reduced risk of all-cause mortality, cardiovascular events and stroke, while monounsaturated fatty acids of mixed animal and plant origin showed no significant effects. Another meta-analysis in 2018 found high-polyphenol olive oil intake was associated with improved measures of total cholesterol, HDL cholesterol, malondialdehyde, and oxidized LDL when compared to low-polyphenol olive oils.