A bottle of olive oil.Olive oil is a vegetable oil obtained from the fruit of the Olive tree (Olea europaea L.), a traditional tree crop of the Mediterranean Basin. It is used in cooking, cosmetics, soaps and as a fuel for traditional oil lamps. Olive oil is regarded as a healthful dietary oil because of its high content of monounsaturated fat (mainly Oleic acid) and polyphenols.

Grades and classification

The International Olive Oil Council (IOOC) sets standards of quality used by the major olive oil producing countries. It officially governs 95 percent of international production, and holds great influence over the rest. IOOC terminology is precise, but it can lead to confusion between the words that describe production and the words used on retail labels. Olive oil is classified by how it was produced, by its chemistry, and by its flavor. All production begins by transforming the olive fruit into olive paste. This paste is then malaxed to allow the microscopic olive droplets to concentrate. The oil is extracted by means of pressure (traditional method) or centrifugation (modern method). After extraction the remnant solid substance, called pomace, still contains a small quantity of oil.

Industrial grades

The several oils extracted from the olive fruit can be classified as:

Virgin means the oil was produced by the use of physical means and no chemical treatment. The term virgin oil referring to production is different from Virgin Oil on a retail label.

Refined means that the oil has been chemically treated to neutralize strong tastes (characterized as defects) and neutralize the acid content (free fatty acids). Refined oil is commonly regarded as lower quality than virgin oil; the retail labels extra-virgin olive oil and virgin olive oil cannot contain any refined oil.

Pomace olive oil means oil extracted from the pomace using chemical solvents — mostly hexane — and by heat.

Quantitative analytical methods determine the oil's acidity, defined as the percent, measured by weight, of free oleic acid in it. This is a measure of the oil's chemical degradation — as the oil degrades, more fatty acids get free from the glycerides, increasing the level of free acidity. Another measure of the oil's chemical degradation is the peroxide level, which measures the degree to which the oil is oxidized (rancid).

In order to classify olive oil by taste, it is subjectively judged by a panel of professional tasters in a blind taste test. This is also called its organoleptic quality.

Among global producers, Spain leads with more than 40% of world production, followed by Italy and Greece. Much of the Spanish crop is exported to Italy, where it is both consumed and repackaged for sale abroad as Italian olive oil. Although boutique groceries sell high-quality Spanish olive oil at a premium, Italian olive oil has the popular reputation for quality. However, chefs will often attest to the superior qualities of Greek olive oil. Incidentally, of these three competitors, Greece has the longest tradition of using the olive tree as a food source.