Specialty Olive Oil Production

November/December 1994

by Paul Vossen, farm advisor, Sonoma CountyCooperative Extension

On the north coast of California several farmers are planting and producing specialty olive oils for sale in top-of-the-line markets. They are attempting to conquer this "new" crop with the same spirit that popularized fine wines, goat cheese, mesclun salad mix, and sun-dried tomatoes. Olive oil, like its similar specialty gastronomic counterparts, is really nothing new. Californians have been producing olive oil since the late 1800s, when thousands of acres of olives were planted (approximately 3,000 acres in Napa and Sonoma Counties remain today); but many orchards were abandoned in the mid 1900s due to competition from low cost imports, mostly from Italy and Spain.

Today a market certainly exists for olive oil, since the U.S. imports about 22 million gallons each year. Interest in the health aspects of olive oil is expanding and increasing demand each year. Most of this imported oil as well as most California oil is inexpensive and has been refined with heat and solvents. California produces about 300,000 gallons of oil each year. Only a very small fraction of this is the gourmet treat classified as extra-virgin and sold from $10 to $40 per liter.

Many of the new olive oil producers are associated with wineries, or have a deep love for Italy and the robustly flavored cuisine of that region. They are producing specialty, finely marketed, extra-virgin oils designed to compete with the Italian imports.

Tuscany in central Italy is currently regarded as the culinary king of olive oil production, world-wide. Most of the finest olive oils in the world are either produced or bottled in northern Italy. Consequently many producers have imported the varieties renowned for their flavor in Tuscany into the similar climatic region of Northern California.

These varieties include: Frantoio, Leccino, Pendolio, Maurino, Moraiolo, and Taggiasca. They are planted approximately 16 to 20 feet apart and are trained as traditional open-center trees. These orchards are still young and do not have good production records yet.

Very good oils have been produced from the dual purpose Mission variety and from carefully handled Marzanillo and Sevillano varieties. The latter two are large-fruited table olives that may yield only 12 to 15 gallons of oil per ton of fruit, while the Mission and Italian varieties may produce 40 to 50 gallons per ton.

There are many production costs necessary to achieve the economic yields of two to six tons per acre yearly.

Olives will survive on very poor sites with shallow soils but will grow very slowly and yield poorly. Deep soils tend to produce excessively vigorous trees, also with lower yields. The ideal site for olive oil production is a clay loam soil with good internal and surface drainage. Irrigation is necessary to produce heavy crops and avoid alternate bearing.

The site must be free of hard winter frosts because major wood damage will occur at temperatures below 15°F. The growing season also must be warm enough so fruits mature before even light fall frosts (usually by early November) because of potential damage to the fruit and oil quality.

Regular pruning should be employed to reduce alternate bearing of trees, to encourage production throughout the tree canopy, and to produce sufficient shoot growth for the next year's flowering and fruiting. Olives bear on the previous year's shoot growth, which is shunted while in competition with an excessively heavy fruit load.

Harvesting is one of the most expensive operations in an olive orchard. The best quality oils come from hand-harvested fruit, which costs $200 per ton. Many growers try to shake, rake, or beat the olives off the trees onto tarps or nets to reduce harvest costs.

To produce the valued extra-virgin oils, high quality fruit is crushed in either stone grinders or metal hammer mills. The paste is then mixed until oil droplets form, and pressed in either single batch hydraulic presses or continuous flow spinning presses. One alternative is a machine that selectively removes the oil from the paste without pressing. The olive juice which contains both water and oil is then separated in "cream-type" centrifuge separators, finally yielding the "liquid gold."

In order to make a profit after all this, the oils are bottled into beautifully decorated etched and labeled containers of various sizes. They are marketed in the finest establishments in the U.S. and served by many three and four star restaurants.

For more information

The California Olive Oil Council is a non-profit organization that educates its members and consumers about specialty olive oil. The council conducts research, tastings, festivals, tours, and educational lectures to disseminate information on the cultivation, processing, distribution, and marketing of olive oil. Contact:

California Olive Oil Council
P.O. Box 7520
Berkeley, CA 94707-0520
Phone: (888) 718-9830
Fax: (510) 528-2271
web site: http://www.cooc.com