Not Just Any Olive Oil

By Robert L. Wolke
Wednesday, November 8, 2006

My mother says that EVOO should not be used for cooking because it can be dangerous to one's health at high temperatures. She tells me that it should be used only for salad dressing. Is that true? If not, what can I say to her to convince her that it is false? If EVOO shouldn't be used for cooking, I doubt that so many of the TV chefs would use it .

For the five or six readers who have not yet seen Rachael Ray on television, EVOO is her much-used shorthand for extra-virgin olive oil. As for your mother, I'm sorry, but she has been misled. Extra-virgin olive oil is no more hazardous to cook with than any other vegetable oil. The "extra virgin" label implies nothing about the effects of heat on the oil.

Here's what you can say to her: "Sorry, Mom: There are no health risks in EVOO. But you're right in line with most experts, who recommend using extra-virgin olive oil only for salad dressing and other table uses rather than for frying. I know you're too smart to waste an expensive oil with great flavor by frying fish in it."

So what does "extra-virgin" mean? It is the olive oil producers' designation of their finest and least processed products. A bit overly romantic, perhaps, but olive oil comes from a romantic part of the world.

The International Olive Oil Council sets the standards for olive oils throughout most of the world (but not in the United States, which doesn't belong to the council) as follows, in decreasing order of quality and, usually, price.

Extra-virgin: Beyond the qualifications for virgin (see below), the oil must exhibit the finest flavor and aroma that its variety of olive and degree of ripeness is capable of producing. And it must contain not more than 0.8 percent of free fatty acids. Fatty acids, which break off from the fat molecules, generally have unpleasant flavors. But recent insights indicate that acidity is not as important a marker of flavor as has traditionally been thought.

Virgin: The oil must be obtained by mechanically pressing a single variety of fruit, physically (not chemically) separating it from the watery juices, and perhaps filtering it. No further processing or refining is permitted. The oil must have excellent flavor and aroma but may contain up to 2 percent acid. A sub-category, "ordinary virgin olive oil," may have up to 3.3 percent acid.

(The designation "first cold-pressed," seen on labels of olive and other vegetable oils, is pure hype. No heat is ever used in the pressing, and there is never a second pressing.)

Refined (formerly labeled "pure olive oil"): A blend of virgin and other olive oils that have been treated to correct flavor defects and reduce acidity to a maximum of 0.3 percent. More than half of the olive oil produced in Mediterranean countries is refined in some way to improve its properties.

Olive oil (with no qualifier): A blend of virgin and refined oils with low acidity but inferior flavor.

Robert L. Wolke ( is professor emeritus of chemistry at the University of Pittsburgh. He can be reached

© 2006 The Washington Post Company