cal treatment with olive oil for newborns "significantly damages the skin barrier" when compared to sunflower oil, and that it may make existing atopic dermatitis worse. The researchers conclude that they do not recommend the use of olive oil for the treatment of dry skin and infant massage.[69]

hen 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." The study also notes that there appears to be much confusion surrounding mineral oil, and that further studies should be done on refined mineral oil to back up claims about its superiority to olive oil.[67] Another trial echoes this claim, stating that olive oil lowers the risk of dermatitis for infants in all gestational stages when compared with emollient cream.[68] However, yet another study found that topical treatment with olive oil for newborns "significantly damages the skin barrier" when compared to sunflower oil, and that it may make existing atopic dermatitis worse. The researchers conclude that they do not recommend the use of olive oil for the treatment of dry skin and infant massage.[69]
Clinical trials have found that olive oil does not act to prevent or reduce stretch marks.[70][71]
The fatty substance was found to reduce inflammation via oleuropein, which is touted for its antioxidant, anti-atherosclerotic, and anti-inflammatory characteristics.[72]
Potential health effects attributed to fat composition[edit]
Preliminary clinical studies provide evidence that consumption of olive oil may lower risk of heart disease risk factors such as lower blood cholesterol levels and reduced LDL cholesterol oxidation,[73] and that it may also possibly influence inflammatory, thrombotic, hypertensive and vasodilatory mechanisms.[36][74][75][76] Although epidemiological studies indicate that a higher proportion of monounsaturated fats in the diet may be linked with a reduction in the risk of coronary heart disease,[77] a cause and effect relationship has not yet been established with sufficient scientific evidence.[78]
In the United States, producers of olive oil may place the following restricted health claim on product labels:
Limited and not conclusive scientific evidence suggests that eating about 2 tbsp. (23 g) of olive oil daily may reduce the risk of coronary heart disease due to the monounsaturated fat in olive oil. To achieve this possible benefit, olive oil is to replace a similar amount of saturated fat and not increase the total number of calories you eat in a day.[79]
This decision was announced November 1, 2004, by the Food and Drug Administration after application was made to the FDA by producers.[80] Similar labels are permitted for foods rich in omega-3 fatty acids such as walnuts and hemp seed.[81]
Other possible effects of olive oil may be a property to balance omega-6 fats and omega-3 fats[citation needed] and to affect blood sugar levels and blood pressure,[82] but these effects were dismissed in reviews by the Scientific Committee of the European Food Safety Authority.[78]
Olive oil contains the monounsaturated fatty acid oleic acid, vitamin E and oleuropein, a chemical that may affect the oxidation of LDL particles.[83]
Preliminary research indicates that olive oil could possi

mixed triglyceride esters of oleic acid and 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. Fatty acid Percentage ref. Oleic acid 55 to 83% [52][53]

 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).[51]
Constituents[edit]



General chemical structure of olive oil (triglyceride). R1, R2 and R3 are alkyl groups (approx. 20%) or alkenyl groups (approx. 80%).
Olive oil is composed mainly of the mixed triglyceride esters of oleic acid and 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.
Fatty acid    Percentage    ref.
Oleic acid    55 to 83%    [52][53]
Linoleic acid    3.5 to 21%    [52][53]
Palmitic acid    7.5 to 20%    [52]
Stearic acid    0.5 to 5%    [52]
α-Linolenic acid    0 to 1.5%    [52]
Phenolic composition[edit]
Olive oil contains polyphenols such as esters of tyrosol and hydroxytyrosol, including oleocanthal and oleuropein,[54] having acidic properties that give extra-virgin unprocessed olive oil its bitter and pungent taste. Olive oil is a source of at least 30 phenolic compounds.[55]
Other phenolic constituents include aldehydic secoiridoids, flavonoids and lignans (acetoxypinoresinol, pinoresinol).[56] The latter two compounds are only present in extra virgin oil.[57]
Hydroxytyrosol (2-(3,4-Di-hydroxyphenyl)-ethanol or DHPE) is a phenolic component of extra-virgin olive oil. An olive oil fraction containing DHPE was shown to inhibit platelet aggregation and eicosanoid (thromboxane B2) formation in vitro.[58] Both hydroxytyrosol and its precursor oleuropein exist in the fruit at levels on the order of 100 times that of shelf extra virgin olive oil. Phenolics are considerably higher in fresh cloudy olive oil than extra virgin that has been separated and aged.
Oleocanthal from olive oil is a non-selective inhibitor of cyclooxygenase (COX) similar to classical NSAIDs like ibuprofen. It has been suggested that long-term consumption of small quantities of this compound from olive oil may be responsible in part for the low incidence of heart disease associated with a Mediterranean diet.[59]
Nutrition[edit]

Olive oil

ore 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 olives are ground into paste using large millstones (traditional method) or steel drums (modern method).

Extraction[edit]



A cold press olive oil machine in Israel.
Main article: Olive oil 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 olives are ground into paste using large millstones (traditional method) or steel drums (modern method).
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.
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).
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