Here is some information about EVOO directly from the California Olive Oil Council.
“‘Extra Virgin’ is the highest grade an oil may receive. International standards dictate that olive oil meets both chemical and sensory standards to be sold as extra virgin. “Extra Virgin” also denotes that the oil is free of defects of flavor or odor. This is evaluated by a trained sensory panel and cannot be detected by laboratory tests.
Unfortunately, in the U.S., many of the oils which are labeled as extra virgin are not required to undergo any such testing. For this reason, in 1998 the California Olive Oil Council established its Seal Certification Program. Under this program, all COOC member producers must comply with the certification process following each harvest to ensure their oil meets the criteria to qualify as extra virgin grade.
Extra virgin olive oil is never better than when it is first pressed. Unlike wine, it does not need time to mature. That gives an impressive advantage to California producers—we get our olive oil to you immediately after harvest, and much more quickly than producers overseas.
The flavor of extra virgin olive oil can be buttery and soft, or spicy and sharp. It can be reminiscent of pepper, lemon or grass. Thanks to California’s range of growing conditions and olive varieties, there truly is a California extra virgin olive oil to suit every palate.
Remember, high quality extra virgin olive oil provides the best health benefits and flavor when it’s fresh. Extra virgin olive oil should be purchased within 12 to 18 months of its harvest date, and should be used up within six months of opening. Be sure to store it in a cool, dark place. When it comes to freshness, there is no better choice than COOC-certified California extra virgin olive oil. See for yourself just how delicious California extra virgin olive oil can be.”