Olive oil ‘fridge test’ doesn’t reliably detect fraud

Mar 21, 2013 Diane Nelson University of California, Davis
Can you determine the purity of your extra virgin olive oil by whether solidifies in the fridge? No, according to new research from the UC Davis Olive Center.
Olive oil ‘fridge test’ doesn’t reliably detect fraud

UC Davis Olive Center Director Dan Flynn.

Extra virgin olive oil is tasty and excellent for your health, but experts say as much as 70 percent of it sold in America is adulterated, or of a lower grade. How can you tell if your brand is the real deal?

One notion — the so-called “fridge-test” theory — says you can determine the purity of your extra virgin olive oil (EVOO) by putting it in your refrigerator. If it solidifies, you can trust your EVOO is pure — or so the theory goes.

Is that scientifically accurate?

No, according to new research from the UC Davis Olive Center. Testing seven samples under cold conditions over eight days, researchers discovered the fridge test is unreliable in detecting either the purity or quality of olive oil.

“None of our samples showed any signs of congealing after 60 hours in a laboratory refrigerator set to 40.5 degrees Fahrenheit,” said Dan Flynn, executive director of the UC Davis Olive Center. “Even after 180 hours, the samples never fully solidified.”

The fridge-test theory surfaced on a recent episode of The Dr. Oz Show which aired Feb. 11, 2013 to more than 3 million viewers. While cautioning his method isn’t fool-proof, Dr. Oz. encouraged viewers to test the purity of EVOO by seeing if it solidifies in the fridge.

“After the show aired, we were swamped with calls from people who were concerned they were being ripped off,” Flynn said.

So the Olive Center conducted a study. They refrigerated seven samples, including two EVOOs, an olive oil, a canola oil, a safflower oil, and two blends. Some samples showed minor congealing at the bottom of the bottles, but none solidified completely.

“It’s true that waxes and long-chain fatty acids in extra virgin olive oil can lead to the oil solidifying in the cold, although relative amounts of these compounds vary from oil to oil,” the study said.

Olive oils are graded based on how the oil is extracted from olives and on the acidity of the pressed oil. True extra virgin olive oil is extracted from olives using only pressure, a process known as cold pressing, as opposed to other mechanical or chemical means. Extra virgin olive oil is more expensive than other grades and considered to have the finest, fruitiest flavor.

Using sensory and chemistry testing, the UC Davis Olive Center is working on dependable methods for detecting when an extra virgin olive oil is fraudulently labeled. In the meantime, the center advises consumers to choose an oil within 15 months of the harvest day (not the best before date), look for a certification seal indicating that the oil passed chemical and sensory tests, and seek (and store) oils protected from light.

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