Olive oil is a fat obtained from the olive (the fruit of Olea europaea; family Oleaceae), a traditional tree crop of the Mediterranean Basin. The oil is produced by pressing whole olives and is commonly used in cooking, cosmetics, pharmaceuticals, and soaps, and as a fuel for traditional oil lamps. Olive oil is used throughout the world and is often associated with Mediterranean countries.
The olive tree is native to the Mediterranean basin; wild olives were collected by Neolithic peoples 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, along the Levantine coast stretching from the Sinai Peninsula and Israel to historic Armenia, or somewhere in the Mesopotamian Fertile Crescent.
Archeological evidence shows that olives were turned into olive oil by 6000 BC and 4500 BC in present-day Israel. 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 2,500 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. The Minoans put the pulp into settling tanks and, when the oil had risen to the top, drained the water from the bottom. 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.
The first recorded oil extraction is known from the Hebrew Bible and took place during the Exodus from Egypt, during the 13th century BC. During this time, the oil was derived through hand-squeezing the berries and stored in special containers under guard of the priests. A commercial mill for non-sacramental use of oil was in use in the tribal Confederation and later in 1000 BC, the fertile crescent, an area consisting of present day Palestine, Lebanon, and Israel. Over 100 olive presses have been found in Tel Miqne (Ekron), where the Biblical Philistines also produced oil. 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 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.
There are many different olive varieties or olives, 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.
Production and consumption
In 2013, world production of virgin olive oil was 2.8 million tonnes (table), a 20% decrease from the 2012 world production of 3.5 million tonnes. Spain produced 1.1 million tonnes or 39% of world production in 2013. 75% of Spain’s production derives from the region of Andalucía, particularly within Jaén province, although many other regions also produce oil.
Although Italy is a net importer of olive oil, it produced 442,000 tonnes in 2013 or 16% of the world’s production (table). Major Italian producers are known as “Città dell’Olio”, “oil cities”; including Lucca, Florence and Siena, in Tuscany. The largest production, however, is harvested in Apulia and Calabria. Greece accounted for 11% of world production in 2013.
Australia now produces a substantial amount of olive oil. Many Australian producers only make premium oils, while a number of corporate growers operate groves of a million trees or more and produce oils for the general market. Australian olive oil is exported to Asia, Europe and the United States.
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, Arizona, and Texas.
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.
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.
• Lampante virgin oil is olive oil extracted by virgin (mechanical) methods but not suitable for human consumption without further refining; lampante is Italian for “glaring”, referring to the earlier use of such oil for burning in 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.
In countries that adhere to the standards of the International Olive Council (IOC), as well as in Australia, and under the voluntary USDA labeling standards in the United States:
• Extra-virgin olive oil Comes from virgin oil production only, and is of higher quality: among other things, 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 Comes from virgin oil production only, but is of slightly lower quality, with free acidity of up to 1.5%, and is judged to have a good taste, but may include some sensory defects.
• Refined olive oil is the olive oil obtained from virgin olive oils by refining methods that do not lead to alterations in the initial 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. This is obtained by refining virgin olive oils with a high acidity level or organoleptic defects that are eliminated after refining. Note that no solvents have been used to extract the oil, but it has been refined with the use of charcoal and other chemical and physical filters. Oils labeled as Pure olive oil or Olive oil are primarily refined olive oil, with a small addition of virgin-production to give 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.
• 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 (80 °F)) 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”.
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.
• PDO and PGI refers 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.
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:
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 unite 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. 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 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.
4. 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. Unfiltered fresh olive oil that has a slightly cloudy appearance is 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 more ecological and less-processed “green” products.
The remaining paste (pomace) still contains a small quantity (about 5–10%) of oil that cannot be extracted by further pressing, but only with chemical solvents. This is done in specialised chemical plants, not in the oil mills. The resulting oil is not “virgin” but “pomace oil”. The term “first press”, sometimes found on bottle labels, is today meaningless, as there is no “second” press; it comes from ancient times of stone presses, when virgin oil was the one produced by battering the olives.
The label term “cold-extraction” on extra virgin olive oils indicates that the olive grinding and stirring was done at a temperature of maximum 25 °C (77 °F), as treatment in higher temperatures risks decreasing the olive oils’ quality (texture, taste and aroma).
One tablespoon of olive oil (13.5 g) contains the following nutritional information according to the USDA:
• Calories: 119
• Fat: 13.50 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)