For thousands of years, humans have been picking, prizing, and pressing the fatty drupes found among the oblong leaves of the gnarled, twisted olive tree into rich, green-gold extra virgin olive oil. And for almost as many thousands of years, humans have been coming up with ways to fake it, to pass off cheaper, less delicious, less nutritious oils as the real thing. The earliest known written mention of olive oil – from Syria, 24 BC – describes how court-appointed inspectors would tour olive oil processing facilities to ensure quality, purity, and the absence of fraud. In ancient Rome, the vessels containing olive oil bore detailed information about the contents, including varietal of fruit used, place of origin, name of producer, the weight and quality of the oil, the name of the importer, plus the name of the official who inspected it and confirmed the previously mentioned data. Let’s just say they really, really liked their olive oil, and that olive oil adulteration has always been an issue.
It continues today, of course, and studies are bearing out the fact that extra virgin olive oil is often adulterated with cheaper, more refined, deodorized olive oils, oils from olives deemed unfit for human consumption, and/or random nut, seed, and vegetable oils spiked with chlorophyll and beta-carotene to replicate the authentic color. An Australian study  found that over half the supermarket EVOO was anything but, even the supposedly legit stuff from the Mediterranean countries; New Zealand researchers had similar results  with Mediterranean imports into their country. Last year, a University of California at Davis study (PDF ) found that 69% of imported extra virgin olive oils failed to meet international standards, while 90% of California EVOO tested passed (the study was partially financed by major California olive oil producers, and producers of some of the failed imports are crying foul ). Similar adulteration is taking place in China , where imported olive oil is mixed with cheap seed oils. In 2007, the New Yorker published a harrowing account of widespread and longstanding fraud in the Italian olive oil industry (“Profits were comparable to cocaine trafficking, with none of the risks”), and more recently, a study  found that four out of five Italian olive oils were “debased.”
I’ve spent the last few years recommending that you eat extra virgin olive oil , and now it appears as if the fraud is pervasive enough to throw everything you thought you knew into a state of confusion. So what are you supposed to do? How do you know if your olive oil is actually olive oil?
The Fridge Test
By now, you’ve probably all heard about it: to test the legitimacy of a supposed olive oil, stick it in the fridge for a day or two. If it begins to solidify, you’ve got yourself a bottle of true extra virgin olive oil. Does it hold true?
Pure monounsaturated fat, also known as oleic acid, solidifies at 39 degrees F. Since olive oil is primarily oleic acid (about 70-85 percent, generally), sticking a bottle of real olive oil in the fridge should elicit solidification. The original olive oil adulterants, sunflower oil  and safflower oil, were mostly polyunsaturated , so adulterating olive oil used to be easy to spot. Now, with high-oleic sunflower oil, high-oleic safflower oil, and high-oleic canola oil on the scene, adulterated olive oil can still solidify in the fridge. Thus, the fridge test is still a necessary, but not sufficient, test for the legitimacy of your extra virgin olive oil. It’s really a test for the degree of monounsaturation in the oils. It’s important (toss any oils that fail the test), but it’s not the full story.
The Taste Test
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 antioxidant plant compounds which make olive oil so good for you. If the olive oil you taste burns the back of your throat and tastes funny to you, chances are you’ve been using and are used to adulterated (or at least non-virgin) oil.
To my knowledge, olive oil adulteration hasn’t progressed to the point where scammers are able to simulate the flavor of true EVOO. If they were to do it, I’d imagine they’d have to add polyphenols or olive extracts to the vegetable oils, and that can’t be cheap. And even if they did add olive extracts and synthetic polyphenols, it’d be better than having none at all.
Does It Matter?
Aside from being cheated out of your money for a disgustingly disappointing mix of soybean and canola oils , can any real health issues arise from consuming adulterated olive oils?
There are allergy concerns, of course, if the adulterant contains an allergen, like peanut oil . Owing to the similarity of its fatty acids to olive oil’s, hazelnut oil is another popular adulterant as well as a fairly common allergen, and one study even showed that people with hazelnut allergies could identify olive oil spiked with hazelnut oil because they suffered symptoms after eating it .
Another health issue that can arise from using adulterated olive oil is the one caused by excessive intake of omega-6 fats from the soybean, sunflower, safflower, canola, or any other cheap high-PUFA  oil being added: generation of inflammatory eicosanoids , systemic inflammation , and oxidized blood lipids. Luckily, the fridge test is sufficient to ferret out PUFA-rich “olive oil” and prevent this from harming you.
Depending on the source and age of the adulterants (year old soybean oil, five month canola, etc), the once robust polyphenol profile of the starter extra virgin olive oil will have been severely diluted. And since the healthful, anti-inflammatory effects of olive oil can mostly be attributed to the polyphenols, olive oil adulterated with inferior, polyphenol-less oils will be less stable, more rancid, and more prone to oxidation. Oxidized oils are not very good for us; here’s why .
I’d say it does matter, and not just because of taste (as if “taste” isn’t reason enough). Here are my roughly recommended guidelines for choosing a good, real EVOO:
My best results have come with domestics – wherever I am. My favorite olive oil here in California is a California olive oil. The best Italian olive oil I ever had was in Italy. Same for Spanish olive oil. In all those studies referenced above, domestics seemed to win out. The NZ and Australian studies found that local oils bested the imports, just as the California study found that the top oils were from California. I’d imagine Italians like Italian olive oil and Spaniards like Spanish olive oil and so on and so forth because they’re not getting the imported, adulterated dregs.
You might have to spend a little money. Sure, I’ve made some good, affordable finds at Trader Joe’s in my day (including a $15 a liter bottle of spicy, unfiltered to the point of clogging the spout, lime green EVOO from Italy that appeared on the shelves for a month or two last year only to disappear before I could grab another bottle), but generally, I’ve gotten what I’ve paid for.
Do some tastings. Look for specialty shops or farmer’s market stands that allow and even encourage tastings of their olive oils. Take at least an ounce (the quarter teaspoon some places try to offer is way too meager to get an accurate reading), slurp it up, and swirl it around in your mouth like you’re trying to make a saliva-EVOO emulsification. Be obnoxious about it, even. But as you swallow the oil, relax and be ready to note the peppery polyphenol kick at the end, usually experienced at the back of your throat. Good EVOO should linger pleasantly in the mouth, even after it’s been swallowed.
Do the fridge test. Even though it won’t prove that your oil is pure, you’ll at least know that your EVOO wasn’t cut with PUFA-rich oils.
Avoid clear bottles. Although I’ve bought some fantastic olive oil from dedicated small-time producers that was stored in random glass jars, I usually opt for EVOO that comes in dark bottles or stainless steel containers. First reason being, light exposure oxidizes olive oil and degrades the polyphenol content. Second reason, most quality olive oil producers care about their product enough to ship it in suitable vessels.
Buy a winner. I always keep up with the latest winners of the Los Angeles International Extra Virgin Olive Oil Competition . Whenever I’ve tried one from the list of winners, I haven’t been disappointed. Here  are some other lauded competitions.
Talk to people who know good olive oil. Talk to olive farmers at the farmers’ market who grow and pick and press and sell the stuff, talk to the mustachioed olive oil aficionado who owns the olive oil shop that you’ve never stopped in to see, talk to your friends who know about this sort of thing and splurge on olive oil all the time.
Ultimately, absent a team of sensory experts, access to gas chromatography equipment, and the ability to astrally project your soul backward through time to the time and place of the oil’s production, there’s no one way to tell, no grand, all knowing test. The closer you are to the proximate producer of the oil (buy “close to the mill”), the fewer times it changes hands before reaching yours, the “feeling” you get from sniffing the herbaceous fragrance, tasting the piquant fruitiness, the enjoyment you derive from it – this is how you determine the worth of your oil. It’s more art than science.
Thanks for reading, folks. Be sure to drop a link or reference to your personal favorite (or favorites) extra virgin olive oil, preferably one that’s widely available or available online, as well as your tips for finding a good brand.