Fatty acid Percentage ref. Oleic acid 55 to 83% [52][53]

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