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Most Of Us Are Blissfully Ignorant About How Much Rancid Olive Oil We Use

You may have heard by now that the olive oil in your kitchen cupboard may be an impostor. After a 2010 report found that 69 percent of imported olive oil in the U.S. failed to meet international standards, thousands of news stories were published, often incorrectly describing the presence of “fake” olive oils in grocery stores. Shoppers everywhere have been terrorized since, afraid that the olive oils on aisle nine may as well be Louis Vuitton bags from New York City’s Canal Street.

The hysteria recently led Congress to assign a new job to the the Food and Drug Administration: sampling imported olive oil to see whether it’s adulterated or fraudulently labeled. That testing and any new regulations that result will probably go a long way in filtering out low-quality oils from grocery shelves. But there’s something that not even the mighty FDA can fix: most of us don’t know the difference between a high- and low-quality olive oil.

Though there’s a long history of scandal in the olive oil world, the problem in the U.S. for consumers is less about oil that isn’t made from olives,1 and more about olive oil that doesn’t meet the quality standards declared on its label. But since most people in the U.S. can’t tell fusty2 and musty3 from pungent4 and fruity,5 low-quality olive oil masquerading as extra virgin is a hard problem to fix.

“We call the U.S. the world’s dumping ground for rancid and defective olive oil. We don’t know the difference,” said Sue Langstaff, a sensory scientist who consults for the beer, wine and olive oil industries, among others. Studies have shown that even frequent olive oil consumers in the U.S. don’t know what the extra virgin or cold pressed designations mean, let alone have the ability to taste the difference. And in blind taste tests, consumers often prefer lower-quality olive oils.

Rancidity, for example, isn’t generally a sought after quality in edible products. And yet, when it comes to olive oil in the U.S., people like it. Why? Partly, because rancid olive oil is less bitter6 than the good stuff. But also, likely because it’s what many of us know and grew up with. It’s what we think olive oil is supposed to taste like.

There’s nothing inherently wrong with liking rancid olive oil. There is, however, a problem with thinking you’re buying extra virgin and getting low-quality oil instead. For starters, because extra virgin oil is harder to make, it commands higher prices. There are also potential health benefits associated with extra virgin oil7 that aren’t necessarily present in lower-quality versions.

The money involved has long left the olive oil industry vulnerable to fraud. In 1959, the United Nations started a council, now called the International Olive Council,8 which was tasked with dealing with olive oil fraud. After decades of experimentation, the IOC came up with a method of tasting that has been used by law in Europe since the 1980s with few changes. It dictates the role of both lab instruments and humans in determining what can be labeled extra virgin olive oil.9 As Langstaff wrote, “With this law, olive oil became the first food in the world whose quality was legally determined at least in part by its sensory properties.”

What she meant is, the extra virgin classification is determined largely using humans as lab instruments — expert tasters trained to perceive 16 defects in olive oil. The presence of defects disqualifies an oil from being classified as extra virgin, though there’s not necessarily something inherently wrong with how the defects taste or smell. Instead, each one is associated with a flaw in the production process. Storage temperatures, exposure to light or oxygen, harvesting methods, the amount of time from harvest to crush, the cleanliness of equipment … each aspect of production can change the chemistry of the oil or produce flavor attributes considered undesirable if it isn’t carefully executed.

When olive oil is oxidized, frequently via light exposure or storage problems, peroxide is formed. When those peroxides decompose, the olive oil gets rancid. Fusty olive oil is created when olives begin to ferment in the absence of oxygen while in storage. More polyphenols generally means more bitter, pungent oil, which is considered positive.

There are some fairly blunt machine tests that can be performed, but ultimately it’s up to humans to determine the quality of olive oil. With training, the mouth and nose go from being a dipstick, which crudely measures good and bad, to a sensitive instrument, capable of discerning small variations in taste and aroma. For an oil to get the designation of extra virgin, it must receive a median score of zero for each defect or an oil will fall from grace, declining in the ranks from “extra” to simply “virgin.” (Fall too far down in these categories, and the olive oil is designated “lampante,” or lamp oil, which is “unfit for human consumption.”)

But Langstaff, who leads a professional olive oil tasting panel, points out this is not how we do things at home. “You’re a human gas chromatograph. You don’t ask if you like the olive oil, you’re just a machine,” she said. Most people lack the language to differentiate their preference for various oils. Unlike with sight and sound, we spend very little time learning about or describing what we taste and smell, which leaves many unable to state their preferences.

But what if we could learn how to better articulate what we like? Consumer research on olive oil preferences is often conducted through a method called descriptive analysis, where the first step involves helping people establish a lexicon for the flavors they perceive. That facilitates data collection, but also gives tasters the tools to refine how they taste.

That’s because having language to describe an experience likely changes the experience itself. We know that language helps us differentiate colors. Light, after all, exists on a spectrum; in many cultures there was no differentiation in language or perception of blue and green until the modern era. And among social scientists, there’s relative agreement that language influences our thoughts and experiences, though there’s debate over the degree of that influence.

Perhaps, then, placing a greater emphasis on learning how to describe what we eat could increase the joy we get from consuming it. It’s difficult to come up with a surefire way to train our palates at home since grocery store offerings can be unreliable. Still, I found a fairly simple experiment useful in beginning to learn the language of olive oil, and the flavors that go with it. Buy a California brand olive oil at the grocery store, one that’s certified by the California Olive Oil Council.10 Then buy a bottle labeled just virgin to compare. Try a sip of each of them solo, to get a sense of their flavors. Since most of us aren’t in the habit of drinking olive oil, the real taste testing comes from then trying the oils on toast, and using them in a cooked dish. Do this with a friend or a notebook, so you can talk about what you’re tasting. For most of us, the first step to experiencing great olive oil is probably learning the language that defines it, and the flavor of those descriptors.

This was an edition of The Digest, a FiveThirtyEight column exploring the science, history and economics of food. We’re still working out the essential ingredients to make this just right — we welcome your feedback and suggestions! You can email me, leave a note in the comments, or find me on Twitter.


  1. Though according to Selina Wang, research director at the University of California, Davis, Olive Center, fake oil is a problem in restaurants and commercial kitchens — not because chefs are choosing oil not made from olives, but because their suppliers are buying fraudulently labeled olive oil.

  2. Olive oil gets fusty when olives are stored in a way that allows them to undergo advanced anaerobic fermentation. People often say it smells like sweaty socks or mushy black olives.

  3. Musty is used to describe the flavor of olive oil made from olives that were stored in humid conditions and have large fungi and yeast content as a result.

  4. Pungent is the tactile sensation, largely felt in the back of the throat, often described as peppery or biting.

  5. The fruitiness of an olive oil is largely determined through the olfactory system, and varies by olive varietal and ripeness.

  6. Bitterness is prized among professionals and considered a positive attribute, along with pungency and fruitiness, but it is disliked by many consumers. Most people have an innate distaste for bitter substances, likely an evolutionary result of the bitterness of many poisonous plant alkaloids.

  7. You can’t trust most of what you read about nutrition studies, but there is more evidence for the benefits of extra virgin olive oil than most “healthy” foods.

  8. Originally called the International Olive Oil Council, it was renamed in 2006.

  9. It also established the method for determining confidence intervals.

  10. I’m not a shill for the California olive oil industry, honest! What makes California notable is that the state has passed a variety of standards that are stricter than national requirements, and several brands have also won gold medals at the New York International Olive Oil Competition this year. At the moment, seeking a California Olive Oil Council seal of approval is a fairly reliable way of getting extra virgin oil if you don’t live near a boutique food store with a knowledgeable buyer.

Anna Maria Barry-Jester is a senior reporter at Kaiser Health News and California Healthline, and formerly a reporter for FiveThirtyEight.


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