To begin with, there are several types of olive oil, each determined by the method of processing.
Virgin olive oil is produced only by physical means, rather than by chemical treatment. The best stuff comes from only ripe olives (as green and overripe olives produce bitter and rancid oil, respectively) ground into a paste using millstones or steel drums. By definition, a virgin olive oil has not undergone any processing other than washing, decanting, centrifuging, and filtering (although none of these are required for virgin oil, nothing else is permitted). Some heat can be applied and, as long as it doesn’t alter the composition of the oil, the process can still be dubbed virgin pressing.
Refined olive oil is poor quality (either due to acid content or other defects) virgin oil that must be refined if it is to be edible. Refining is usually done with charcoal filters or chemical processes. Refined olive oil is more shelf-stable, but it’s also essentially flavorless.
Olive pomace oil is extracted from the olive solids (pomace) leftover from the pressing, usually with chemical solvents. This isn’t really olive oil, and it’s definitely not meant to be eaten. Most olive oil-based soaps you see are made with olive pomace oil.
Blended olive oil is, in my opinion, to be generally avoided. While it can be a blend of different olive oil varieties, it’s usually blended with canola or some other vegetable oil. You’ll get increased shelf life and polyunsaturated fat content along with less monounsaturated fat. No thanks.
Light olive oil isn’t actually less caloric; it just lacks flavor. Besides, why would anyone want to eat less monounsaturated fats?
Extra virgin olive oil is widely regarded as the pinnacle of olive oils. According to the International Olive Oil Council (of which, beware, the United States is not a member), extra virgin olive oil must contain at most 0.8% acidity, with a “superior taste.” Extra virgin can also be unfiltered (which deepens the flavor and reduces shelf life) or cold-pressed (wherein the pressing is slow and gradual, without generating much frictional heat, and which results in better flavors). Extra virgin also contains the most polyphenols, which are some of my favorite antioxidants.
What to Look For – A Few Things to Keep in Mind About Olive Oil
Just because something is labeled “extra virgin,” though, doesn’t mean it’s necessarily good. In fact, rather than buying a mid-priced or inexpensive bottle of Italian or Greek extra virgin olive oil, you might look for a local – or at least domestic – brand. Those extra virgins are fragile oils, and the journey from the Mediterranean can result in a bland bottle. I’ve also read that a lot of the extra virgin that makes it over here in mass quantities isn’t worth it (and that’s been my experience, sadly).
When choosing an oil, treat it a bit like wine and engage your senses. Smell it – it should smell like olives, very clean and almost like grass and apples. Don’t rely too much on sight – the color of an oil is easily manipulated. Instead, go with the one that really matters: taste. Take a half teaspoon or so into your mouth and swirl it around (again, like wine). First and foremost, it should taste like olives, but there are other flavors in the best oils. Grassiness, apples, even fennel are pretty common in really great olive oil. If it’s metallic-tasting, it’s probably rancid. If it’s light, delicious, and barely coats your mouth (without feeling greasy), it’s probably great stuff. And then my favorite part, the finish. The best oils from the first harvest with the highest antioxidant content will leave a spicy finish on your throat, like mild peppers.
Just experiment. Keep trying them until you find one you like. The different varietals are all unique, so your journey might be a long one.
The thing with olive oil is that you need to use it the right way. The best extra virgin, unfiltered, cold-pressed olive oil should never be used to sauté something because heat can mar the delicate flavor. Instead, use high quality stuff as a finisher. Cook with butter then top the dish off with your prized extra virgin oil. That way, the taste and nutritional benefits are retained without wasting any of your precious nectar on a cast iron skillet.
Store your oil in a cool, dark place. Heat and light are now your biggest enemies (be sure to buy an oil in a dark bottle). Extra virgin is the least stable, so keep it at a good temp (somewhere between 57 and 65 degrees, like a wine cellar). You can refrigerate other olive oils if your kitchen is too hot, but refrigerating extra virgin olive oil can disrupt the delicate flavors. If you get extra virgin that’s tasty enough, of course, you won’t have to worry about long-term storage – you’ll be guzzling it straight out of the bottle.