Here’s a quick glossary of the grades you’ll see on olive oil bottles:
Extra virgin olive oil (highest grade). This must meet numerous chemical parameters (including a free fatty acid content of 0.08 percent or less) and a sensory standard of zero defects (such as fermented or rancid flavors), with some fruitiness.
Virgin olive oil. This grade has slight defects of aroma or flavor and meets a lower chemical standard, including higher free fatty acid levels. Both virgin and extra virgin olive oils must be extracted from the olives by mechanical means, without the use of solvents.
Refined olive oil blends (includes pure olive oil and extra-light olive oil). If a virgin olive oil does not qualify for the virgin designation as defined by its acidity level and other factors, the oil is refined to remove off-odors and off-flavors. The result is a bland oil that is blended with small amounts of virgin olive oil to give it some olive flavor and color.
This article first appeared in the UC Berkeley Wellness Letter.