When Gary Beauchamp went to Erice, Italy in 1999 for the series of lectures that spawned what is now known molecular gastronomy, he attended an olive oil tasting. The symposium’s attendees smelled and sipped the viscous oil from clear glasses. “We were drinking it,” he said, “and, all of a sudden, my throat started to burn.”
The sensation reminded him of the burn that comes when you chew up ibuprofen. It tingles or itches. It makes you cough or, ahem, clear your throat. Sure enough, in 2005, Beauchamp, a biologist at Philadelphia's Monell Chemical Senses Center, and other researchers showed that extra-virgin olive oil contains a cough-eliciting compound they called oleocanthal, a distinguishing chemical characteristic of fresh-pressed olive oil.
Generally, "extra-virgin" oil is pressed or centrifuged and meets certain requirements set forward by the International Olive Council. But since the United States Department of Agriculture, which enacted new rules for "extra-virgin" oils (PDF) last October, does not enforce the voluntary rules, "extra-virgin" labels in the U.S. are essentially a marketing term intended for unheated, unrefined oil with low acidity and superior taste.
What's remarkable about that prickly, itchy, tickling sensation is that it comes from anti-inflammatory compounds that are very similar to ibuprofen. In a study published earlier this year in the Journal of Neuroscience, scientists said oleocanthal binds to the same TRPA1 receptors in our oropharyx that ibuprofen does.
The sensory research underscores our long-standing reverence for the medicinal properties of olive oil. One familiar food writing trope explains that olive oil was only sold in English drugstores, as a laxative or for treating earaches, before Elizabeth David's cookbooks appeared in the 1950s. More recently, olive oil has become a linchpin for the "Mediterranean Diet," although its benefits can be as uncertain as an oil's origins.
Earlier this month, the University of California Davis Olive Center released a report (PDF), which, found for the second year in a row, signs that imported olive oil brands failed to deliver on international standards for extra virgin oils. Panels of sensory experts found that top-selling brands—Colavita, Star, Bertolli, Filippo Berio, and Pompeian—failed international standards for extra virgin oils. (This study was funded by the California Olive Oil Council, which, no doubt, gains from results showing a much lower failure rate for its oils).
But the other factor at play here brings us back to the sensation in the back of our throats. We like familiar foods, and, it appears, we expect off-flavored oils. Another pair of researchers from the Olive Center conducted a survey in northern California, doling out a taste of 22 different oils to 110 consumers. They found that people liked oils with nutty, ripe fruit, green tea, butter, green fruit, and grassy attributes, but also, they wrote, "attributes that are characteristic of defective oils—rancidity, mustiness, fustiness and winey ﬂavor."
So the distinctive burn of extra-virgin olive oil indicates its phenolic content, which may underlie its health benefits, but one thing is clear: a pharmacological understanding of oleocanthal alone can’t be a universal measure for good or pure oils. (After all, you could dilute or adulterate olive oil and still have a detectable burn.)
As our appetite for olive oil continues grows, it’s important to remember how these objective chemical analyses combine with the subjective appreciation of experts, and "extra virgin" implies more than being pressed for the very first time.
Top photo (cc) by Flickr user fdecomit.
Middle chart via "Sensory Characterization of the Irritant Properties of Oleocanthal, a Natural Anti-Inflammatory Agent in Extra Virgin Olive Oils" ©2009 Oxford University Press.
Bottom chart via "How do consumer hedonic ratings for extra virgin olive oil relate to quality ratings by experts and descriptive analysis ratings?" © 2010 Elsevier.