Davis Researchers Put Olive Oil ‘Fridge Test’ to the Test

On a recent episode of the Emmy Award-winning television program, “The Dr. Oz Show,” Dr. Oz warned his audience that more than two-thirds of extra virgin olive oil sold was not pure EVOO. He recommended that viewers paying premium prices to get EVOO should conduct a home test to find out if their purchase is pure EVOO quality. Dr. Oz advised buyers to put their bottle of EVOO into the refrigerator to see if the oil solidifies. If it does solidify, they can be “pretty sure it’s pure,” said Dr. Oz; though he also cautioned that the test is “not 100 percent foolproof.”

Some experts debunk the so-called “Fridge Test,” including expert taster Richard Gawel who called the test a “myth” and the North American Olive Oil Association that described it as “completely false and misleading.”

The University of California Davis Olive Center recently put the Fridge Test to the test. Olive Center Director Dan Flynn, who was a guest on Dr. Oz’s show, said that there were many calls and emails to his office, supermarkets and producers after the program aired. Viewers who had tried the test and found their oil failed had concerns and questions. Flynn said Olive Center Research Director Selina Wang had the idea for the team to conduct its own research experiment to “help clear up the confusion.”

Flynn told Olive Oil Times that the results of the experiment, which were released today, showed that the Fridge Test is an unreliable indicator of olive oil quality.

Seven oil samples, including EVOO, lesser grade olive oils, olive oil blends and non-olive oils were placed in a refrigerator and checked at intervals up to 180 hours. Although no samples fully solidified, a sample of EVOO mixed with up to 50 percent lesser grade olive oil congealed in the bottles, meaning it could be interpreted as passing the refrigerator test even though it was not pure EVOO. The study concluded that the Fridge Test is not reliable for determining oil purity or quality.

If the Fridge Test cannot be relied on, what can consumers do? Flynn advises consumers to buy darker bottles that protect the oil from light, purchase oil within 15 months of the harvest date (which should be printed on the label) and look for certification seals.

Flynn recommends certifications that include both a chemical profile test and a sensory evaluation, such as the Australian and Californian certifications. The NAOOA, which represents American olive oil importers, also conducts a quality seal program that includes analyses by a certified taste panel.

Chemical tests alone are “not enough to tell if an oil tastes good,” said Flynn.


Refrigeration is not reliable in detecting olive oil adulteration, UCD Olive Center

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This article was last updated October 14, 2014 - 2:46 PM (GMT-5)

  • Rono

    Finally we can all stop talking about this. Thanks UCD.

  • Jason

    Something from Dr. Oz debunked? Shocked, I’m shocked, I tell you…

    • Hayward

      Shocked AND appalled!

  • Jon

    This is useful. Unfortunately, a small percentage of the millions of people that watch Dr. Oz will ever see this study.

    Also, no one seems to have done a study that shows “dark glass” is better for olive oil and some research shows that it could even be worse as the coloring agent they add to the glass in fact may allow more harmful UV light to pass through the glass.

  • Basil Smith

    Sadly to those millions of vacuous-minded viewers who believe that every thing that is screened on reality TV shows (such as the Dr OZ show) is in fact reality. Truth is not or is rarely the issue. The utterances of their hosts are regarded as infallible…..A retraction by the producers or Dr Oz himself, would be beneficial.

    As a consumer I have no idea as to whether the product I am purchasing is in fact and truth EVOO or not. I rely upon the container’s label and this publication to inform me.
    In this regard it would be helpful if an independent national (or international) OO standards board was established whose role (among others) was to certify the purity of OO.

    Given the info that has emerged re false declarations and fraud on a grand scale in the industry, it tarnished image could do with such a body.


    Very sad , but Olive Oil industry W/O Fraud is not possible nowdays. We ll see in 20 years.

  • http://www.facebook.com/oliveoilsoap Adia Osteen

    Interesting ,, Thanks

  • John Kalmatiz

    Per the results of that study, you can – at the very least – say that if an oil stays completely liquid after five days in the refrigerator, it is *not* unrefined olive oil. Unrefined oils should not have been “winterized”. Combined with the high levels of triglycerides containing oleic acid, these oils should not stay completely liquid in the refrigerator.

    Though it tells you little about quality, the fridge test may be able to tell you something about the identity of the oil. The oils not produced from olives (canola, safflower) do not pass the test, and oils with less than 50% extra virgin oil also did not pass the test.

    The test can be sped up simply by lowering the volume of oil use – oil in a small glass will work.

    The “Extra Virgin” oil from a common brand available in America, imported from Europe, completely fails this test. Therefore, I think it’s fair to say that it is likely to have been adulterated with oil from another species of plant, or with refined olive oil, as has been recently reported.

    Conceivably this test could be easily fooled by adulteration with coconut or palm oil, but I have not read any reports about that happening yet.