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CSI: Olive Oil

SACRAMENTO, Calif. — Paul Vossen remembers the typical Italian olive oil junket of 30 years ago. Visiting olive oil professionals witnessed vats of fresh olive oil pressed from olives taken straight from nearby Tuscan olive groves. But the tour also went to another area of the facility, says Vossen, which was shown to them proudly and without secrecy. Here, olive oil of lesser quality was refined — stripped of off-odors and aromas — and added like standard equipment to the fresh oil.

What ended up in retail containers was definitely olive oil. But don’t call it extra-virgin. And have no illusions that it’s got much in the way of healthful properties, like antioxidants.

Vossen, based in Santa Rosa, Calif., and a long-time olive oil expert with the University of California, Davis, says time’s run out for unscrupulous blenders to manipulate olive oil for profit.

To be extra-virgin, olive oil can’t be rancid, adulterated with cheap refined olive oil, or diluted with lesser oils. “We’ve known for years there’s been outright fraud,” Vossen says. Common adulterations pad olive oil with hazelnut oil, or seed oils such as canola oil, or refined olive oil. Slap on an extra-virgin label, and such products can fetch a premium price.

Study reveals mislabeling

But a study released last month by UC Davis puts this practice on notice, even if fraud is attempted in infinitesimal amounts. The study rocked the olive oil industry and prompted chefs to sue importers who were cited in the university’s research as selling inferior oil mislabeled as high-quality extra-virgin olive oil.

While the companies called out in the UC-Davis findings haven’t individually denied that they routinely sell blended or adulterated oil, their importers have claimed the study is unfair because it applies new testing standards.

New international grading standards may not have been the UC-Davis researchers’ goal, but their use of new forensics on olive oil purity can reveal the age of the oil, nail the percentage of PPPs and DAGs (more on those later) and indicate if some non-olive oil sneaked in.

“We have our own ‘CSI: Olive Oil’ here,” says Dr. Charles Shoemaker, the chemist who manages the Olive Oil Chemistry Lab at the Robert Mondavi Institute for Food and Wine Science on the UC Davis campus. “It’s become a very sophisticated practice, the adulteration of olive oil throughout the world.”

The windows in Shoemaker’s lab overlook the Davis campus’ 2,000 olive trees. Inside, the decor is cement bunker with beakers, test tubes and chemistry toys.

“We have lots of magnetic stirring bars because there’s a lot of mixing that goes on in a chemistry lab,” Shoemaker says, tapping a few small stirrers on a metal surface and waving one like a pointer.

The lab’s equipment uncovers defects, degradation and dilution in extra-virgin olive oil. Spectroscopic studies look for oxidation. That means the oil’s old or rancid. To be fair, any oil could suffer indignities during shipping, like a slow boat through the Panama Canal or storage in a hot warehouse.

But other tests go deeper. A key test for DAGs (three kinds of diacylglycerols) profiles certain fatty acids. It’s so specific that if profiles don’t match up, it could mean an olive oil is doctored with seed or nut oil, such as soybean, sunflower or canola.

Another test employed by the UC Davis study measures PPPs, which is a breakdown of chlorophylls. All olive oils have chlorophyll, particularly oil made from early harvest green olives. But chlorophyll degrades significantly and rapidly when olive oil is refined.

Shoemaker uses a pricey gizmo that makes a giant sucking sound as it vacuums solvents and isolates the chlorophyll. “It takes about 25 minutes per sample for just this one step,” Shoemaker says.

For the study, Davis did some of the tests. A lab in Australia did others. In all, 104 bottles of olive oil were purchased in Los Angeles, Sacramento and San Francisco — same brands, same lots — during the first week in March 2010. These included 14 imported brands and five labels from California. All were labeled extra-virgin.

Most of the California oils came out clean. But many big-name imports did not fare well. Testing revealed Bertolli, Filippo Berio, Pompeian, Colavita, Star and Carapelli samples labeled extra-virgin olive oil did not pass tests to qualify for the extra-virgin grade.

Critical reaction

The study came immediately under fire for several reasons.

First, it was funded by the California Olive Oil Council and a pair of California olive oil producers, giving the impression of bias in favor of the California samples. Second, the UC Davis tests included measures for DAGs and PPPs, as yet unrecognized by standards of the International Olive Council headquartered in Spain.

Bob Bauer of the North American Olive Oil Assn., which represents importers, called the study irresponsible. “These results directly contradict our 20 years of more extensive sampling than what those results show,” Bauer says.

But Vossen and Shoemaker say the IOC tests don’t go far enough and should one day analyze for PPPs and DAGs. “Everybody holds the IOC as some divine standard,” Vossen says. “But that standard is a minimum standard.”

The U.S. is not a member of the IOC. But growing concern over truth-in-olive-oil-labeling has drawn in the U.S.Department of Agriculture, which recently announced revised standards for olive oil sold in the United States, the first since 1948.

“We’re taking the snake oil out of olive oil,” says Mike Jarvis, acting director of the USDA’s Agriculture Marketing Service.

Beginning Oct. 25, olive oil from every olive oil-producing country, including the United States, could be subject to random sampling off retail shelves, using a lab in Blakely, Ga.


Zester Daily contributor Elaine Corn is a James Beard Award-winning cookbook author and food editor. A former editor at the Louisville Courier-Journal and the Sacramento Bee, Corn has written six cookbooks and contributed food stories to National Public Radio.

Photo: Olive oil.
Credit: Syagci.

Zester Daily contributor Elaine Corn is a James Beard Award-winning cookbook author and food editor. A former editor at the Louisville Courier-Journal and The Sacramento Bee, Corn has written six cookbooks and contributed food stories to National Public Radio.