Adulterated or Fake Olive Oil
by Catherine Haug, Jan 22, 2014
Olive oil has become very popular in recent years, and not just in the kitchen; it can also be used as a skin moisturizer. It is great for salad dressings and marinades, and for medium-low heat cooking, such as sautéing or braising. However, it should not be used for higher heat cooking, such as browning meats or deep frying.
Inevitably, now that it is so popular, some companies have found a way to increase their profits from the sale of olive oil by – gasp! – diluting it with cheaper oils such as GMO corn, soy or canola oil.
If you test your olive oil using the at-home tests described below, let me know what you find and I’ll add it to this article.
Testing for Purity of Olive OIl
Back in 2010, UC Davis published information about adulterated olive oil (2). They tested 124 different samples from eight major brands (6,7), both domestic and imported, and found that 69% of imported, and 10% of domestic (California-based) oils labeled as olive oil or extra virgin olive oil, did not meet international and USDA standards.
Beginning in 2011, Duke University publishes information on adulterated olive oil; those results can be found on FoodFraud.org (1); on their site, click the Search tab, and type ‘Olive oil’ in the search field to get the results. Duke researchers used DNA analysis, as well as other methods to identify the plant sources of oils in the mix. What did they find? corn, soy, safflower, canola and other inexpensive oils, most of which are likely GMO (1, 2), some with green coloring added to look like olive oil. .
How can you tell if the olive oil you use is pure?
You can send a sample of your oil toUC Davis Olive Center (4) for testing. But short of that, here are some general indicators:
- Beige-colored olive oil in plastic bottles, or clear glass bottles is most likely adulterated.
- Olive oil in dark-colored bottles or steel cans is more likely pure, but you should still do an at-home test (see below).
- If the oil is clear (not cloudy), it is suspect, but cloudiness can be faked, so you should still do the at-home test.
- Most imported extra virgin olive oils are questionable for authenticity.
- California-based olive oils are most likely pure, especially those that have the name of the orchard on the label.
- Imported olive oils certified by the IOC are most likely pure.
- Price can also be an indicator; that is, inexpensive olive oils are more likely to be impure. However, expensive olive oils can be using price to assure you of purity when they may in fact be adulterated.
At-home tests for pure olive oil
These tests are by no means infallible, but it’s a good place to start. For the most definitive test, send a sample of your oil to UC Davis Olive Center (4) for testing.
The fridge test
Put your bottle of oil in the refrigerator overnight. After chilling, inspect the oil: (5)
- If is still all-liquid, it is highly likely it is adulterated, because the mono-unsaturated fats that are so prized in olive oil will solidify at refrigeration temperatures.
- If it is solid or mostly solid, it is likely to be pure. However, olive oil adulterated with high-oleic sunflower, high-oleic safflower and/or high-oleic canola oil behave like olive oil when refrigerated, so this test is not 100% accurate.
Note that some pure olive oils are winterized (chilled and filtered) and will fail the fridge test, even though they are pure. It would thicken but not solidify so the test would be indeterminate. (6)
The taste test
If your oil passed the fridge test (it solidified), next do the taste test (5). “Good olive oil is often bitter, pungent, spicy, and slightly abrasive. It’s not always smooth and easy going. In fact, the “off-notes,” the intense flavors that make the uninitiated screw up their face actually indicate the presence of high levels of polyphenols” (those peppery compounds that make olive oil so healthful). (6). If your oil burns the back of your throat or tastes “funny,” it is probably pure olive oil.
However, olive extracts and polyphenols can be added to adulterated oils, and those pass the taste test even though they are not pure olive oil.
The oil lamp test
Pure extra-virgin olive oil will keep an oil lamp burning. So pour some in an oil lamp and ignite the wick. If it continues to burn, it is fairly likely to be olive oil. If it won’t’burn, it is NOT extra virgin olive oil, and contains refined oils which are mostly likely not olive oil at all.
However, there are other oils besides olive oil that will burn in an oil lamp, so this test is not definitive. (6)
List of tested brands
These lists are based on testing at UC Davis in 2010. Most likely those found to be adulterated are still adulterated, but some of the ‘pure’ brands may no longer be so reliable.
Brands that failed to meet international and USDA standards for pure olive oil and are likely adulterated ( 2):
- Filippo Berio
- Newman’s Own
- Rachel Ray
- Whole Foods
The following brands met the standards back in the 2010 study ( 2):
- Corto Olive
- California Olive Ranch
- Kirkland Organic
- Lucero Olive Oil (Ascolano)
- McEvoy Ranch Organics
Cat’s Fridge Testing
I’ve been using Western Family brand of imported olive oil (from Harvest Foods) for a couple years, because it has a good price. But when I learned of this adulteration problem, I became suspicious. I put some of the oil in the fridge for 3 days and it never solidified. A very bad sign. I didn’t even bother to do the taste test because the fridge test was fairly definitive. Also it comes in a clear bottle, another bad sign.
Next I bought a dark-colored bottle of Spectrum brand Organic Mediterranean Extra Virgin Olive Oil, from Spain or Tunisia (per the label). It was slightly cloudy at room temperature, and started to solidify after only 1 hour in the refrigerator. It was mostly solidified by the next day. Then I tasted it, and noted its peppery flavor. This oil cost twice as much os the Western Family olive oil, but I want the real deal. I’m not 100% sure it’s is pure, but I’m going to trust it.
I have also tried a bottle of olive oil from a named orchard in California, another trustworthy sign. It came in a dark bottle that was corked, like wine. slightly cloudy at room temperature and easily solidified in the fridge. Also had a nice ‘green olive’ flavor, slightly peppery. It is more expensive than the Spectrum Organic olive oil, so I buy it only when the store is out of Spectrum.
A friend had a different brand of Organic olive oil she bought at Costco, so she did the fridge test. It did not solidify at all, so may well be adulterated; or it may be pure but ”winterized’. (6)
Another friend, who lives in Israel, tells me that the big Italian brands are most suspect while middle-eastern brands are more trustworthy.