Olive Oil


The olive and the tree on which it grows have been revered since ancient times. Archaeological digs have unearthed evidence that olive trees existed on the island of Crete in 3500 B.C. The Semitic peoples were cultivating the tree's fruit by 3000 B.C. They particularly liked to use the oil of the olive to anoint the body during religious ceremonies, and to light their lamps. An ancient Hebrew law prohibiting the destruction of any olive tree is still obeyed.

By the time of the Roman Empire, olives were a mainstay of the agricultural economy. The Romans also used the oil to grease the axles of wagons and chariots. The Greeks traded it for wheat; the elaborately decorated clay pots that they used to transport the oil became part of the civilization's burgeoning art industry.

The olive tree is mentioned frequently in the Koran and in the Bible. Noah receives the message that land is near when a dove arrives at the ark with an olive branch in its mouth. Greek mythology associates the goddess Athena with the olive tree and credits Acropos, the founder of Athens, with teaching the Greeks to extract oil from the tree's fruit.

A member of the evergreen family, the olive tree features a gnarled trunk and leaves with a silvery underside. Its strong root system is perfect for penetrating sand, limestone, or heavy, poorly aerated soil. The trees thrive best in regions with rainy winters and hot, dry summers. Although it may take up to eight years before a tree produces its first harvest, a single tree can live for centuries.

Early oil producers pressed the olives by crushing them between huge cone-shaped stones as they turned slowly on a base of granite. Today, most factories employ hydraulic presses, exerting hundreds of tons of pressure, to separate the oil from the olive paste. Spain and Italy are the primary commercial producers of olives and olive oil. Greece is close behind them. However, California, Australia, and South Africa are emerging as leaders in the industry. Some wineries are planting olives to offset poor wine harvests. Ironically, olive trees were planted in California by missionaries in the 1800s, which by the turn of the century were producing an excellent grade of olive oil. However, the market demand was weak so the trees were uprooted and grape vines were planted in their place.

In the late twentieth century, emphasis on good nutrition and a fascination with the so-called Mediterranean diet has resulted in a resurgence in the olive oil trade. Olive oil is touted as a monounsaturate that is healthier for human consumption than corn and vegetable oils. The oil is also promoted as a dandruff reliever and, when mixed with beeswax, a homemade lip balm. In the late 1990s, the United States and Canada consumed olive oil at a yearly rate of 147,600 tons (150,000 metric tons). The demand often exceeds the supply, and during the 1990s prices rose significantly.

Raw Materials

The primary ingredient of olive oil is the oil that is expressed from ripe olives. In the late spring, small flowers appear on the olive trees. Wind pollination results in the blossoming of the olives, which reach their

Olive Oil
peak oil content approximately six months later. Thus, the olives are harvested from November to March, after they have progressed in color from green to reddish violet to black. It is often necessary to harvest olives from the same trees several times in order to gather olives at the same stage of maturation.

Since ancient times, workers have knocked the fruit from the trees with long-handled poles. The process has not changed significantly over the centuries. Modern poles resemble rakes. Originally, nets were spread under the tree to catch the falling olives. Many producers are now using plastic covers to cushion the fall and to allow for cleaner, faster gathering.

One quart (0.95 L) of extra virgin olive oil, the highest level of quality, requires 2,000 olives. The only added ingredient in extra virgin olive oil is the warm water used to flush away the bittemess of the olives, caused by the presence of oleuropein. Extra virgin olive oil contains not more than 1% oleic acid. Pure olive oil, that which results from the second pressing, is often mixed with extra virgin olive oil. The commercial, or non-edible, grades are put through a refining process that may leave traces of soda solutions and bleaching carbons.

Olive Oil

The Manufacturing

Collecting and grading the olives

Washing and milling the olives

Creating an olive paste through malaxation

Cold-pressing the olive paste to extract the oil

Separating the oil from the vegetable water

Storing and packaging the oil

Quality Control

The olive oil industry is regulated by government food agencies, such as the Food and Drug Administration (FDA) in the United States. By regulation, olive is classified into five grades. Virgin olive oil is that which is obtained from the first pressing. Pure is a mixture of refined and virgin oil. Refined, or commercial, consists of the lower grade lampante oil from which the acid, color, and odor have been removed through processing. Lampante is a highly acidic grade; its name is derived from its use as lamp oil. Sulfide olive oil is chemically extracted from the olives through the use of solvents and is refined many times.

The popularity of olive oil in the late twentieth century has spawned many bottlers who are combining various grades of olive oil and labeling them illegally as virgin or pure. A 1995 FDA report charged that only 4% of the 73 domestically produced or distributed olive oils it tested were pure. The North American Olive Oil Association disputed the findings, stating that of the 300 oils the association tests each year, only a handful are found to be impure. In any event, the situation has become one of "buyer beware."

The Future

Finding workers who are willing to perform the laborious task of picking olives is becoming more difficult. Therefore, the olive oil industry is pursuing methods for mechanizing the collecting process. Among the larger olive oil companies, centrifugation methods are becoming more popular for the pressing process as well as for separating the oil from the vegetable water. Although centrifugation requires more energy and water, the method takes up less space in the factory and requires a shorter set-up time. Centrifugation also eliminates the need for pressing bags, which must be washed after each pressing.

Where to Learn More


Benavides, Lisa. "For Olive Importers, It's All Greek to Them." Boston Business Journal, October, 25, 1996, p. 3.

Burros, Marian. "Eating Well." The New York Times, October 23, 1996, p. C3.

"From the Olive Tree to Olive Oil." Pompeian, Inc.

"Green, With Envy." Prevention, August 1996, p. 106.

Muto, Sheila. "Impurity of Olive Oil Is Raising Concerns." The New York Times, January 3, 1996, p. C2.

Mary F. McNulty

User Contributions:

david kirrage
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May 11, 2006 @ 3:15 pm
The only added ingredient in extra virgin olive oil is the warm water used to flush away the bittemess of the olives.

Jane Simian
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Jun 21, 2008 @ 6:18 pm
Can the waste pulp that remains after the pressing of the olives be used as fertilizer for the soil? Is it true that from the picking time to the beginning of the pressing of the olives not more than one hour can go by?
Many thanks for answering my questions from Argentina

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