ANATOMY OF OIL
Oils are liquid fats (as opposed to solid fats, such as butter or shortening) - so 100% of any oil's calories come from fat.
Oils are derived from plant sources - nuts (such as walnuts), seeds (such as sesame seeds), plants (such as rapesee), and fruits (such as olives or avocados).
Many oils are low in saturated fat and high in heart-healthy monounsaturated and polyunsaturated fats.
STORAGE SAVY
Light, oxygen, and heat are oil's enemies, which can cause your precious "liquid gold" to spoil. Store oils in tightly sealed, colored glass or opaque containers in a cool, dark place; a cabinet or pantry is ideal. If you purchase your "liquid gold" in a clear container/bottle, not to worry, as the producer probably wants YOU to see the color and quality of their EVOO. It's best to buy oils in small quantities, unless, of course, you're a heavy user....then, if available, buy in 1/2 or 1 gallon sizes.
OILS & NUTRITION
Several comprehensive studies have revealed that overall fat consumption, as long as it remains moderate (30% calories or less from fat), isn't as much of a concern to our health as the types of fat we consume.
Substituting monounsaturated and polyunsaturated fats (like those found in cooking oils) for saturated and trans fats (found mostly in fatty meats and processed foods, respectively) may actually reduce harmful LDL, and monounsaturated fat may raise beneficial HDL cholesterol, helping to lower your risk of heart disease.
FLAVORED OILS
Many oils are superb flavor carriers, which means you can infuse them with just about any seasoning you choose. Choose your favorite oil. For a Mediterranean flair, infus olive oil with crushed garlic and rosemary. For an Asian dish, infuse sesame or peanut oil with hot chilies. If you have truffle shavings, choose a neutral-tasting oil, such as canola or regular olive oil, that won't overpower the truffles' exotic flavor.
Smash or slice ingredients to release their natural flavors (chilies, lemon rind, basil, garlic, and truffles are some suggestions), and heat over very low heat for 5 minutes (approx), turn off the heat and cool. We recommend that you use your flavored oil only for the meal that you are serving, after which discard the leftovers.
FAVORITE OILS
Extra Virgin Olive Oil: This oil has a rich range of flavors, from pungent and bold to smooth and buttery. In Europe, olive oils labeled "extra virgin" must meet strict classifications. In the United States, while there are no nationwide standards, the term generally means a minimally processed oil. Olive oil from California that is certified by the COOC which carries the COOC Certified Seal meets requirements similar to those in Europe - known as the International Olive Council (IOC).
Many high-end and imported extra virgin olive oils state on the bottle where the olives came from and the varietal or varietals that were used to produce that particular oil.
Olive oils range in colors from pale golden to deep emerald and has a pronounced fruity - sometimes peppery - taste. Because the flavor of extra virgin olive oil can diminish with heat, it's often used to finish a dish, drizzled over pasta, soups, or whisked into a vinaigrette.
Regular Olive Oil: Also called "pure" or "light" olive oil, which are simply marketing tags and not an indication of nutritional qualities, this olive oil is a blend of refined olive oil and extra virgin olive oil. It costs less and has a mild flavor. Use it when you want to preserve the flavors of the food rather than impart the character of the oil to it. It is often used for sautes or stir-fries.
TECHNICALLY SPEAKING
You'll see the following designations touted on product labels and in descriptions of many oils. Here's what they mean.
Extra Virgin: According to the standards set by the IOC, extra virgin olive oil must be unrefined, with an acidity level of less than 0.8%. "Virgin" oil is also unprocessed oil, but of inferior quality, with acidity levels of up to 2%. Be aware that the United States is not a member of the IOC, which means that oil made and marketed here as "extra virgin" may not adhere to the same quality controls. FYI: The COOC has much stronger and stricter standards than the IOC. AND this is a "good thing".
Cold Pressed (aka First Pressed): The flavor of some delicate oils is compromised if they become too hot during processing, so they may be treated in a controlled temperate environment. In the US, this term is largely unregulated and often not a true indication of quality.
Unfiltered: The most flavorful and aromatic of oils, these are also the most fragile. It's best to store them appropriately in a dark cool cupboard or pantry.
FYI - unfiltered is welcomed by chefs and olive oil foodies.
Expeller Pressed: This term means the oil was literally squeezed from the nut, seed, or olive paste using pressure. Oils that are not expeller pressed are extracted by soaking the grounds in a chemical solvent (usually hexane) and then boiling it off, which removes any flavor or aroma from the oil.
Refined: These oils have been chemically treated to make them more shelf-stable and neutral in flavor, color, and aroma. Unrefined oils maintain more flavor and often have a cloudy appearance.
Smoke Point: The temperature at which oil begins to emit fumes and decompose is called the smoke point. If oil reaches this point, it will produce an unpleasant taste in the food that it's cooked in. A first wisp of smoke is fine, but if it is allowed to intensify, you'll need to (carefully) discard it and start over. In general, refined oils have a higher smoke point than unrefined oils.