I’m confused by the descriptions I see on oil labels — cold-pressed, expeller-pressed, extra virgin, etc. What do these terms mean, and which terms indicate quality?
Your confusion is understandable. Oil labeling is complex, with a few terms that have legal meaning, many terms that are mere marketing hype, and some terms that are downright misleading. Like most foods, oils are most flavorful and nutritious when they are fresh and minimally processed. But manufacturers are always looking for ways to do things faster and cheaper and make foods last longer on the shelf.
Four processes are used to extract oils from nuts and seeds: grinding, pressing, heating, and applying chemical solvents. Corn, soy and canola oils are typically processed using the chemical solvent hexane. Olive, avocado, walnut, peanut and most other oils are usually expeller-pressed.
Here’s how Spectrum, a leading producer of high-quality oils, explains expeller-pressed vs. cold-pressed:
“Expeller pressing is a chemical-free, mechanical process that extracts oil from seeds and nuts. This method of oil extraction is an alternative to the hexane-extraction method used for many conventional oils. The temperature reached during pressing depends on the hardness of the nut or seed. The harder the nut or seed, the more pressure required to extract the oil, which in turn creates more friction and higher heat. There is no external heat applied during the expeller pressing. Delicate oils, or those in which flavor nuances are a key component, need to be treated with greater care in controlling processing factors. Oils that are cold-pressed are also expeller-pressed, but in a heat-controlled environment to keep temperatures below 120 degrees Fahrenheit.”
According to Spectrum, Europe has rigorous standards in place for the terminology of cold-pressing (“fully unrefined oil extracted at temperatures below 122 degrees”), but the phrase “cold-pressed” has been used erroneously in the United States for a number of years, often employed as a marketing technique for oils that have been expeller-pressed or even refined (which exposes the oil to temperatures of up to 470 degrees).
The term “extra virgin” is also not regulated in the United States. A 2012 University of California, Davis study discovered that 86 percent of imported olive oils labeled “extra virgin” actually weren’t, failing the criteria because of oxidation, adulteration or poor manufacturing methods. Nine out of 10 California olive oil samples, on the other hand, were properly labeled.
Unfortunately, because most terms to describe oil processing are not defined by law or enforced, consumers just have to find brands they can trust. The UC Davis study includes charts indicating which brands were properly labeled “extra virgin.” California Olive Ranch, Corto Olive, Kirkland Organic and McEvoy Ranch were among the brands that sell legitimately labeled olive oil.
Vicki Mattern is a contributing editor for MOTHER EARTH NEWS magazine, book editor and freelance magazine writer. She has edited or co-authored seven books on gardening, and lives and works from her home in northwestern Montana. You can find Vicki on Google+.