Like wine, no two olive oils are exactly alike. Each oil is distinct, a unique product of soil, climate, olive type (there are at least 60 varieties of olives) and processing method. And like wine, olive oil is a changing, “living food."
The olive tree, the domesticated Olea Europaea, is a hearty evergreen with silver-green leaves that thrives in the mild winters and long hot summers of the Mediterranean and does well in dry, arid climates. In many cases olive trees, which start bearing usable fruit after five to eight years, can be hundreds of years old and still produce fruit.
There are about 800 million olive trees in the world, growing in places as disparate as Australia and California, but 98 percent of the world’s olive oil comes from the 20 or so countries that make up the International Olive Oil Council. The IOOC operates under a United Nations treaty and sets standards of quality for member countries. Spain is the largest producer of olive oil in the world, followed closely by Italy. Greece is the third-largest producer, though it uses more olive oil per capita than any other country.
Worldwide, about 10 million metric tons of olives are produced each year. A million metric tons are used for table olives and nine million (93 percent of the total crop) are pressed for olive oil. A mature olive tree will produce only 15 to 20 kilograms (33 to 44 pounds) of olives each year. Since it takes about five kilograms of olives to make a liter of oil, one tree is capable of producing only about three to four liters of oil per year—a small output by any measure.
The olive is a drupe, a fruit like the peach and the plum, with a single hard stone. An olive branch will bear 10 to 40 clusters of the fruit. As the olive ripens, the flesh fills out, and six to eight months after the tree’s blossoms first appear, the olives are fully ripe, yielding their maximum oil content.
Once the fruit is ripe, pickers traditionally stand on ladders propped on the branches and pick each olive by hand, dropping them into net bags. Hand picking assures that each olive is not damaged, and that only the fully ripe olives are picked. While olives are also harvested by machines, these mechanical harvesters make no distinction between the unripe and ripe olives.
The olives are immediately taken to an olive oil mill where they are pressed for their oil the same day, or at most a day later, before they start to oxidize and ferment. It is one of the great ironies of nature that the actual fruit of the tree—the just-picked olives—are far too bitter and acrid to eat. The fruit must be washed and soaked and then either brined or salted and allowed to age before it is edible. Virgin olive oil, however, is extracted without heat, additives or solvents from the freshly picked bitter olives, and should have a lush, rich taste and velvety texture; it is ready to use immediately after extraction.
Olive oil that is “cold-pressed” is made from olives that have been crushed with a traditional millstone or stainless steel grindstone. No heat or chemicals are added during the process, which produces a heavy olive paste. The paste is then spread over thick, round straw or plastic mats that are placed in a press. This press extracts the liquid from the paste—a combination of oil and water. The oil is separated from the water either by decanting or by centrifuge and then filtered to remove any large particles.
The resulting oil is then graded and classified, according to standards established by the IOOC. The finest oil has the lowest acidity, which is measured as a percentage per 100 grams of oil.
Extra Virgin: If the olive oil has certain taste characteristics and 1 percent or less total acidity, it can be classified as extra virgin, considered to have perfect taste and aroma. Because of its purity, distinct taste, and limited production, extra virgin olive oil is the most expensive.
Virgin: The next grade down, virgin olive oil is produced without heat or additives, just like extra virgin. Virgin olive oil has excellent taste and aroma, but may have a higher acidity than extra virgin, anywhere up to 2 percent. “Ordinary virgin olive oil,” rarely available in this country, may have up to 3.3 percent acidity.
Olive Oil: The most widely marketed grade of olive oil is simply called “olive oil,” the new term for what was previously called “pure olive oil,” or “100 percent pure olive oil.” Often less than a quarter of the price of extra virgin, olive oil has an acidity level of less than 1.5 percent and is a blend of refined olive oil and virgin olive oil. The amount of virgin in a blended oil varies from 5 to 25 percent, depending on the flavor desired by the producer. The new “lite” olive oils—lighter in flavor and texture, but identical in calories and fat composition to virgin—are part of this blended category.
Olive-Pomace Oil: This oil is extracted from pomace, the pulpy olive residue from which the virgin olive oil has been extracted. Extraction is done with the aid of solvents (in the same manner in which seed oils are produced), then the oil is blended with virgin olive oil. Pomace is usually the least expensive olive-derived oil product but may not be sold as olive oil. Production is limited and continues to decline because of advances in olive pressing technology.
Storing olive oil
As long as it is properly cared for, olive oil has a long shelf life. Because of its antioxidants, it will remain fresh longer than other oils and in a restaurant setting will be consumed before there is a loss of flavor. Under proper conditions, olive oil may last up to 12 months (18 months if stored in metal containers). Light, heat and air are destructive to olive oil, so the best way to buy it is in tins or dark glass bottles. The best place to store well-sealed containers is in a cool, dark place.
Oive oil can also be refrigerated, though it will become hazy. A good compromise for a hot kitchen is to store large amounts in the refrigerator, and pour out small amounts that will be used up quickly.
Occasionally, extra virgin oil will have particles floating in it. Not to worry. This is unfiltered olive oil, considered prime oil in the producing countries. The tiny bits of pressed olives that have been left in the oil add flavor and color.
How to choose an oil
Personal taste, cost effectiveness and availability are important issues when choosing olive oils. But what appeals to you may not necessarily be the choice of a colleague. Nature, fortunately, has provided a wide range of styles and flavors.
It would be easy if different grades of olive oil could be categorized by taste, but that’s not the case. Some extra virgin oils will be very rich but mild, others will be fruity and delicate, and there are those whose peppery smell and taste almost bites back. The extra virgin olive oils of small producers may vary in taste from year to year, much like the output of small wineries. The olive oil from large producers, particularly those who do a lot of exporting, tends to be consistent.
Culinary professionals who are familiar with olive oil contend that they can tell an oil’s country of origin, even in a blind tasting. What is probably true in most cases, however, is that they recognize a style that is associated with a country.
Olive oil does not have to come from a particular country in order for it to be bottled and labeled there; however, the quality of the oil and its labeled grade must meet IOOC specs. The actual oil can come from different regions of the same country, or from one or several other countries, although a producer will usually try to replicate his or her “national taste.”
In order to re-create the authentic taste of a dish some chefs will purposely match up particular olive oils to specific dishes—Spanish oil for a paella, Greek oil for making mezze, a French oil from Provence for a tapenade. Often, restaurants will keep several olive oils on hand—an extra virgin for some cold dishes and dining room service; a virgin for sautéing, braising, roasting and grilling; a pomace for frying.
Terms to know
Anti-oxidant: A substance that increases the useful life of a fat or oil because it reduces the rate at which the fat becomes rancid. Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are examples of manufactured anti-oxidants allowed by the U.S. Food and Drug Administration for use in foods.
Flash point: The temperature at which an oil will flame but not continue to burn (650ºF for olive oil).
Foaming: The development and persistence of froth on the surface of fats or oils during frying. Foaming can indicate fat breakdown, but may also result from the presence of foreign material.
Hydrogenated: The addition of hydrogen to the molecule of an unsaturated oil or fat to make it solid.
polyunsaturated: A fatty acid with two free carbon links. Oils from plant foods and fish contain the most abundant amounts of polyunsaturated fats, with coconut oil as an exception.
Pro-oxident: A substance that speeds up the reaction of fats with oxygen. Copper and iron are pro-oxidants.
saturated: A fatty acid with no free carbon links. Unsaturated fats have a greater potential to develop rancidity. When hydrogen is added to an unsaturated oil, the fatty acid becomes saturated and changes from a liquid to a solid.
Smoke point: The temperature at which oil gives the first trace of smoke when heated at a specified rate. A high smoke point is desirable for a fat used for frying and indicates good refining, but the length of total frying time before a fat starts to smoke is a better test of stability. Good frying oil will have a smoke point of 420ºF to 450ºF (the smoke point for olive oil is 437ºF).
Careful with flavored oils
Olive oil suffused with garlic, herbs or hot peppers have become popular recently not only because of their flavors, but because many of them are appealing to the eye. They can, however, become a breeding ground for botulism, so it is important to exercise caution when making any kind of flavored oil.
Avoid using low-acid, fresh ingredients, like raw garlic or fresh herbs, to infuse oil meant to last awhile. When these ingredients are combined with olive oil, an anaerobic environment (without oxygen) can result and create harmful bacteria.
If you want to use fresh ingredients for your infused olive oil, make it in small quantities. The oil may be refrigerated for up to two days before being discarded.
Infused oils made with dried ingredients are much safer and just as potent as those made with fresh products.