A good bottle of olive oil is a requirement for just about every kitchen. From drizzling over vegetables or meats to crafting salad dressings and bread dips, a little olive oil can make your cooking sing. But how much do you need to spend for a quality olive oil, and how long will it last once opened? Is extra-virgin olive oil all that it purports to be?
Dan Flynn, executive director at the University of California at Davis Olive Oil Center; and Darrell Corti, a frequent olive oil competition judge, provide answers.
The olive harvest typically begins in early November, and more consumers are turning to olive oil for their culinary needs. According to Flynn, about 2 million gallons of olive oil are expected to be produced statewide in 2012 -- about double the amount from the previous year. Like wine, sorting through rows of olive oils at the store sometimes feels like a guessing game. Quality can range greatly, as will flavor profiles, which span from fairly neutral to very pungent.
"The quality of olive oils are based on the variety (of olive used), the time of their picking and the type of extraction used," said Corti. "All oils have a flavor character that's pungent and bitter. That's the normal flavor component of an olive. You want the oil to retain its bitterness and pungency."
So, let's start with shopping.
Let's say there's a great price on a gallon of olive oil that seems hard to pass up. Well, unless you plan to cook a lot with olive oil and use it fairly fast, it's best to buy these oils in smaller amounts.
The best olive oil is the freshest olive oil, and as with wine, oxygen is an enemy. Once a bottle is opened and oxygen gets introduced in the bottle, that's the start of an oxidation process that leads to declines in flavor and aroma. Olive oils contain fatty acids that can help fight off oxidation, but in the end, oxygen will always win. Plan on using up that bottle within weeks.
"As you use the oil, you're going to add some head space into the bottle, and that's how oil gets oxidized," said Flynn. "I try and use an oil as quickly as I can. Six to eight weeks can be good. If you can't use it in that time, you're maybe buying too big a container."
Unopened bottles of olive oil can last up to two years if stored properly, and their flavors can soften with extended time in the bottle.
"Keep them in a cool, dark place -- and buy them often," said Corti.
Heed the harvest date stamped on the bottle. This assumes your olive oil bottle comes stamped with a harvest date. If not, that's a key indicator that your oil likely isn't of the best quality. Some olive oils might have a "best by" date instead, but harvest date will be a better indicator of how fresh your oil may be.
"A 'best by' date is important as well, but we've found in some studies that a lot of that oil has already gone south," said Flynn. "They had some rancid and off flavors, but were within the 'best by' date. Look for the harvest date. Every olive oil, no matter how good it starts out, is going to decline."
The term "extra-virgin" is supposed to connote the utmost in olive oil purity. By definition, an extra-virgin olive oil must be free of defects, while exhibiting a certain measure of fruitiness. The oil must also be extracted solely by mechanical means, and no solvents may be used during processing, among other factors. Such standards are set by the International Olive Council, the United States Department of Agriculture and other bodies. Tasting panels also are used to determine if an olive oil is indeed extra-virgin.