Can you cook with olive oil on high heat? Is all high-quality oil from Italy? Nutritionist Carrie Dennett debunks the olive-oil myths.

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On Nutrition

You might not think of olive oil as having a harvest season, but it does — just like any other fruit. Extra virgin olive oil (EVOO) is unique among oils because it’s essentially fruit juice — the olive “fruit” is mechanically crushed to extract the “juice.” This is quite different from the process used to extract oil from seeds like canola, sunflower and safflower, which usually involves chemical solvents.

Olive oil plays an integral role in the Mediterranean diet and is rich in health-promoting phytonutrients, antioxidants and monounsaturated fats. Despite this, it has been hounded by several myths that won’t seem to die. Let me take a shot at them:

1. Most olive oil is adulterated. This myth stems from reports published by the University of California, Davis several years ago suggesting that more than two-thirds of EVOO sold in California did not meet quality standards. According to Dan Flynn, executive director of the UC Davis Olive Center, EVOO has to have some fruitiness and be free of defects like fustiness (when the olives start to ferment before pressing), mustiness (when olives start to mold before pressing) or rancidity (which means the oil started to oxidize before or during processing).

Unfortunately, the fact that many of the tested oils lacked fruitiness, or were fusty, musty or rancid has been widely misinterpreted to mean the “failed” oils were adulterated with either inferior olive oil or with other oils like canola. So how did this disconnect happen? “It partly got misinterpreted because it’s easier in the media to report that something’s fake,” Flynn said. “It also plays into the bigger story about inauthenticity in food.” He also suspects that many people who wrote about the report didn’t actually read it.

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The North American Olive Oil Association (NAOOA) guards against adulteration through random testing. “While there are rare instances of adulteration, the NAOOA’s testing of hundreds of bottles each year confirms that it’s actually a very rare occurrence today,” said Eryn Balch, NAOOA’s executive vice president. “Unfortunately, the misconception is stronger than ever due to the reach of blogs and social media that promote inaccurate claims.”

2. It’s not healthful to cook with EVOO. Think that olive oil isn’t safe to use above moderate heats? Think again. EVOO loses some of its unique flavor during cooking, but it doesn’t become unhealthful.

Balch said that while it’s true that EVOO has a lower “smoke point” (the point when an oil starts to smoke and break down and produce unhealthful free radicals) than refined oils like canola oil, vegetable oils and light olive oil, its smoke point is high enough to be a healthful choice for almost all types of cooking we do at home. “Mediterranean countries, especially Greece, cook everything in extra-virgin olive oil,” Balch said.

She points out that smoke point depends partly on the quality, age and condition of the oil. Good-quality EVOO is safe in a range of 350-410 degrees, in part because it is rich in antioxidants, which protect the oil from becoming damaged when heated. Poor quality oil, or oil that has gone rancid, will have a lower smoke point.

3. You can tell a quality olive oil by looking at it. Quality olive oil isn’t a generic product. According to the NAOOA, variance based on factors like olive variety, growing conditions and country of origin creates variability in oil color — from pale yellow to dark green — and how fast the oil will cloud or solidify in the refrigerator.

Flynn said an oil’s color is worth admiring, but it says nothing about the quality. “Many people think, ‘If the oil’s really green, I’m going to be looking for an early harvest peppery oil, but if it’s golden I’m going to be looking for a late harvest buttery oil.’ ” Not necessarily true.

4. It matters where olive oil comes from. Flynn said it’s a mistake to assume an olive oil is good just because it comes from, say, Italy, Greece or California. “The origin in terms of the state or country is not that important from the standpoint of quality,” he said. “Quality comes down to the producer level. Just because olive oil has been made somewhere for a long time doesn’t mean that everything that comes out of that place is going to be great.”

Less than 4 percent of the olive oil consumed in this country is produced here — with most of the rest coming from Mediterranean countries. California produces about 99 percent of domestic olive oil, but stop in at a Seattle-area Whole Foods and you can buy nearly local olive oil from Oregon Olive Mill in Dayton, the only commercial olive-oil mill north of the California border.

Oregon Olive Mill general manager and head miller K. Paul Durant takes quality seriously. Most of the mill’s olives come from family farms in California, because demand for his oil far exceeds the supply of fruit from his young crop of olive trees. A few weeks ago, an olive farm in Northern California harvested 24 tons of olives in the morning, loaded them on a truck, and sent them north. Durant started processing those olives that evening. “That fruit is in such great condition when they are machine picked,” he said. “The other beauty is that the temperature as they travel through Oregon is lower.”

The harvest season runs almost constantly from mid-October to mid-December, and the freshly pressed oil is stored in stainless-steel tanks in a temperature-controlled room before and after filtering (some processors use plastic, which allows oxygen in and can lead to rancidity). “We bottle every week, and we put the milling date and the bottling date on the label.” Durant doesn’t like “best by” dates, calling them arbitrary.

5. Olive oil gets better with age. Flynn says a quality oil should last two years after bottling time, provided it is stored in a capped bottle away from light and heat, and that a harvest date on the bottle is often a good indicator of quality. “The fact that a producer cares that a consumer knows when the oil was harvested tends to indicate that the producer is ‘above the bar,’ ” he said. Shoppers can also look for quality seals from the NAOOA, USDA, California Olive Oil Council or the Extra Virgin Alliance.