Olive Oil Introduction - Cooking Tips

Olive oil has been one of the staples of the Mediterranean diet for thousands of years and its popularity is growing rapidly in other parts of the world. It is one of the most versatile oils for cooking and it enhances the taste of many foods. It is an excellent alternative to butter or margarine as a condiment or for use in food preparation.

Olive oil is the only type of vegetable/fruit oil that can be obtained from just pressing. Most other types of popular oils (corn, canola, etc.) must be processed in other ways to obtain the oil. (Oil from some seeds and nuts, such as sesame and peanut, can be obtained through pressing.) Another important bonus is that olive oil has proven health benefits.

Olive Growing

Most countries that line the Mediterranean Sea produce olive oil in varying quantities. Spain, Italy, and Greece represent more than three-fourths of the total olive oil output in the world.

• The largest producer, Spain, supplies about one-third of the olive oil in the world. The olive oil produced in Spain is exported to nearly 100 countries.
• Italy is the second largest producer, with one-fourth of the world's total production. Italy exports a large quantity of olive oil to countries that enjoy the distinctive flavors of Italian oil, but Italians consume so much olive oil that they must also import a large quantity. The average consumption in Italy is about 10 quarts of olive oil per person per year.
• Greece is the third largest producer, representing about one-fifth of the world's total production. With a consumption of about 20 quarts per person per year, the Greeks are the largest consumers of olive oil per person in the world.
• Other major olive oil producers in the Mediterranean region are Turkey, Tunisia, Portugal, Morocco, and France with smaller amounts produced in the remaining Mediterranean countries.

There are several other countries outside the Mediterranean that are suitable for olive growing and olive oil production. These include South Africa, Chile, Argentina, Australia, New Zealand, and the United States (nearly all of the production is based in California, because of its Mediterranean climate).

Olive trees thrive in climates with mild winters and hot summers. They cannot tolerate a temperature of less than 10ºF, and a lengthy spell of freezing weather can ruin any chances for a decent crop. Olive trees are very hardy in hot summer temperatures and they are drought tolerant. The trees grow best in shallow soil.

As ripening occurs, most olives change from green to purple to dark red to black. About 10 pounds of olives are required to produce 1 quart of olive oil. Most olive trees can provide enough olives to produce about 3 quarts of oil and some trees may provide 3 times that quantity.

Harvesting

Olives must be harvested at the correct time in order to obtain the greatest quantity of oil without an increase in the acidity level. The experienced olive grower knows the exact time when the olives should be harvested. Olives that are picked too soon may contain no oil. Olives contain oil soon after they have turned a light green color and the volume of oil increases as they become darker green and then change to purple or black. If the olives are allowed to ripen too long, the volume of oil will continue to increase as will the acidity level, which has a negative impact on the quality.

In the Northern Hemisphere, olives are generally harvested from late October through February. Harvesting usually occurs in November for most of the olive crop in Spain. October is the beginning of harvest time in the Tuscany region of Italy when the olives are still solid and green. In Greece, some olive varieties may be picked in October when they are still green, while other varieties may be left until February when they are at the peak of ripeness and bursting with oil.

Harvesting the olives has always been a labor intensive and time consuming process. Hand picking is still the best method for harvesting an entire crop because it causes the least amount of bruising to the fruit, (fruit that is bruised will have a negative impact on the resulting oil) but it is not very practical for large operations. Some individual growers, known as single estate producers, still harvest olives by hand picking to achieve the highest possible quality in the finished oil. Harvesting methods and the time of the harvest vary greatly depending on the country or region where the olives are grown, the type of olives that are grown, and the climatic conditions. Some of the various harvesting methods include:

• Hand picking.
• Beating the trees with large poles to loosen the olives.
• Using large wooden or plastic devices to "comb" through the foliage and loosen the olives.
• Collecting olives as they fall to the ground naturally.
• Machine harvesting, using a tractor that has vibrating claws that shake the tree and branches. The olives drop into nets, which helps to minimize bruising. The branch shaking equipment cannot harvest all of the olives from the tree, so the remaining olives must be picked by hand.

Pressing

Olives are usually pressed within 24 hours if the weather is hot. If the weather is cooler, the pressing may occur within 72 hours of harvesting. In many olive growing countries, the olives must be pressed within 72 hours to qualify as virgin oil. The longer the time between harvesting and pressing, the greater the chance that the olives will begin to ferment and the greater the chance that the resulting olive oil will not be the top quality possible.

In addition to the limited time available between harvesting and pressing, to be considered virgin or extra virgin, the oil must be obtained with the use of mechanical processes only. If heat and/or chemical processes are used to produce the olive oil, it cannot be called virgin or extra virgin.

A process, known as the "first cold pressing," yields olive oil with the best flavor and in most cases the highest quality possible. After harvesting, any remaining leaves are removed, the olives are washed, and are ground into a pulp using a revolving mill, usually constructed with stainless steel. Granite millstones were traditionally used before modern equipment became widely available. The entire olive, including the pit, is pressed to produce the oil.

Some single estate producers, collect the oil that results from just the initial crushing while many other producers use an additional step to extract more oil. The olive pulp is placed on mats constructed with hemp or polypropylene that are stacked and then pressed to squeeze the pulp. Oil and water filter through the mats to a collection tank below. The water and oil are then separated in a centrifuge.

Regardless of the method used for the first pressing, the temperature of the oil during production is extremely important in order to maintain the distinct characteristics of the oil. If the temperature of the oil climbs above 86ºF, it will be damaged and cannot be considered cold-pressed.

If the natural acidity of cold-pressed oil is less than 1% oleic acid, it is known as extra virgin olive oil. If the acidity is between 1% and 3.3%, the oil is called virgin olive oil. Any oil obtained from the first cold pressing that has a natural acidity above 3.3% cannot be sold as virgin olive oil. It is usually sent to a refinery to reduce the acidity and eliminate any other objectionable characteristics.

Up to 90% of the oil is obtained from the olives during the first cold pressing. The remaining 10% is extracted in refineries that use heat and/or chemical processes to remove the oil.

Basic Olive Oil Grades

Three basic grades of olive oil are most often available to the consumer:

• Extra Virgin
• Virgin
• Olive Oil

In addition to the basic grades, olive oil differs from one country or region to another because of the types of olives that are grown, the environmental factors of the area, the harvesting methods, the time of the harvest, and the pressing techniques. These factors all contribute to the individual characteristics of the olive oil. Some of the characteristics found in olive oils produced in some of the major olive growing areas are:

• Spain: golden-yellow, fruity, aromatic, almondy
• Italy: deep green, peppery, herbal, grassy
• Greece: green, strong, aromatic
• France: pale, sweet, mild, light
• Portugal: golden, strong, fully ripe
• California: mild, light, fruity