Mueller's new book, Extra Virginity: The Sublime and Scandalous World of Olive Oil

NPR - interview! You can listen to it here

Mueller's new book, Extra Virginity: The Sublime and Scandalous World of Olive Oil, chronicles how resellers have added lower-priced, lower-grade oils and artificial coloring to extra-virgin olive oil, before passing the new adulterated substance along the supply chain. (One olive oil producer told Mueller that 50 percent of the olive oil sold in the United States is, in some ways, adulterated.)

The term "extra-virgin olive oil" means the olive oil has been made from crushed olives and is not refined in any way by chemical solvents or high heat.

"The legal definition simply says it has to pass certain chemical tests, and in a sensory way it has to taste and smell vaguely of fresh olives, because it's a fruit, and have no faults," he tells Fresh Air's Terry Gross. "But many of the extra-virgin olive oils on our shelves today in America don't clear [the legal definition]."

Extra-virgin olive oil wasn't created until stainless steel milling techniques were introduced in the 1960s and '70s. The technology allowed people to make much more refined olive oil.

"In the past, the technology that had been used had been used really by the Romans," says Mueller. "You grounded the olives with stone mills [and] you crushed them with presses."

The introduction of stainless steel milling techniques has allowed manufacturers to make more complex and flavorful extra-virgin olive oils, he says. But the process is also incredibly expensive — it costs a lot to properly store and mill extra-virgin olive oil. Mueller says that's why some people blend extra-virgin olive oil with lower-grade, lower-priced products.

"Naturally the honest people are getting terribly undercut," he says. "There's a huge unfair advantage in favor of the bad stuff. At the same time, consumers are being defrauded of the health and culinary benefits of great olive oil."

Bad or rancid olive oil loses the antioxidant and anti-inflammatory properties of olive oil, says Mueller. "What [good olive oil] gets you from a health perspective is a cocktail of 200+ highly beneficial ingredients that explain why olive oil has been the heart of the Mediterranean diet," he says. "Bad olives have free radicals and impurities, and then you've lost that wonderful cocktail ... that you get from fresh fruit, from real extra-virgin olive oil."

Your Olive oil may not be as virgin as you think it is.

The next time you reach for a bottle of extra-virgin olive oil, beware. A new study from the University of California- Davis claims more than two-thirds of random samples of imported so-called extra-virgin olive oil don't make the grade.

The Olive Oil Chemistry Lab overlooks many of the 2,000 olive trees on the Davis campus.

"It's like we have our own CSI: Olive Oil lab here," says chemist Charles Shoemaker, who manages the lab's forensics.

To be extra-virgin, olive oil can't be rancid or doctored with lesser oils. Shoemaker wasn't all that surprised that many of the 14 major brands failed certain tests.

"It's become a very sophisticated practice, the adulteration of olive oil throughout the world," Shoemaker says. He says the lab can prove defects, degradation and dilution in olive oil beyond what human taste buds can figure out. The lab testing zeroes in on specific flaws.

"We do spectroscopic studies looking for oxidation," he says. That means the oil's old or spoiled. Shoemaker also tests fatty acids "to make sure the oil is all from olives and not from soybean, sunflower or other types of oil."

The UC-Davis Olive Oil Report


No molecule can hide. Shoemaker revs up a small vacuum that removes solvents and isolates chlorophyll, which is always in oil made from green olives, but never in lesser-grade seed oil. As it sucks a sample, he's patient.

"It takes about 25 minutes per sample to do just this one step," he says.

The UC-Davis study was funded in part by the California Olive Oil Council. Oils were tested by some methods not yet recognized by international standards. For that reason, Bob Bauer of the North American Olive Oil Association, which represents importers, disputes the Davis study.

"It's irresponsible to create the misperception that they've done based on unrecognized tests," he says. "These results directly contradict our 20 years of more extensive sampling than what those results show."

There's never been a legal definition in the U.S. for any grade of olive oil, but mounting concern over truth-in-olive-oil-labeling has drawn in the USDA, and new American regulations will conform to international standards. Starting in October, olive oil from every olive oil-producing country, including America, will be subject to random sampling off retail shelve.