Olive oil is a kitchen fundamental, but if you’re a kitchen novice, a complete beginner, or the kind of person doesn’t care about cooking at all and is only doing it to survive (there’s absolutely nothing wrong with that!), trying to make sense of it can be a bit overwhelming.
Olive oil cannot be thought of in the same way that cooking oils like vegetable or canola are—think of it in the same way you think about wine: you want to use a cheap bottle if you’re cooking, but you never want to cook something you wouldn’t also want to drink. (Or, in olive oil’s case, enjoy drizzled atop a warm, crusty piece of bread with a light sprinkle of sea salt, and maybe a glass or two of the good wine you save all for yourself.) Here are some basic things you need to know about olive oil, and what you should be considering when buying it.
Olive oil has been a part of Mediterranean cuisine for at least 6,000 years, and the extraction process used for millennia is still used by some producers today: pressing. Back in the times of the Greeks and Romans this was done simply with heavy stones, and though technology has advanced quite a bit since then, high-end stone-pressed olive oils are still being made by some niche farms and culinary artisans.
Olive oil cannot be thought of in the same way that cooking oils like vegetable or canola are—think of it in the same way you think about wine.
Until the mid-20th century nearly all olive oil was made by pressing, and it was the system that gave birth to nearly all the terms we use to describe it today. About 90-percent of an olive’s oil would be extracted from the first pressing and was labeled virgin; the oil was then graded for quality, with the most premium being labeled as extra virgin (or premium extra virgin), and lesser-quality oils labeled as virgin, fine virgin, or semifine virgin. If the oils were process with chemicals or heated past 80-degrees Fahrenheit they were stripped of their virgin-status—a rule that still stands today. Many olive oil manufacturers will print terms like “cold pressed,” “first pressed” and “first cold pressed” on their labels to create an impression of exceptional quality, even though those terms are true for literally all virgin olive oils and therefore completely meaningless.
Today, most olive oil production is not pressed, but crushed. First, the olives are loaded into machinery where steel rollers grind them into a paste. Then, water is slowly added to the paste which causes the oil molecules to separate from the olive pulp and clump together. The paste is then put into a centrifuge to separate the oil and water from the pulp; the water is then removed, and the oil is graded. Though it isn’t pressed in the traditional sense, this oil is still allowed to be classified as virgin, and as long as it is not heated, it can still be considered cold “pressed.” Any oil that doesn’t meet the standards to be called extra-virgin is refined to remove any impurities, which also removes much of the characteristic olive flavor. Sometimes flavor is added by blending with a small amount of extra-virgin and is sold as regular or classic olive oil, which is not very good when eaten raw (such as in a salad dressing), but is perfecly fine when used in small quantities for cooking.
After processing, leftover olive pulp can be treated with chemicals to extract even more oil, which is called pomace. This olive oil is incredibly cheap, because, well, it’s not good: it lacks the flavor and health benefits of virgin olive oil, and is best avoided. Also steer clear of bottles that are labeled as light olive oil or olive oil blend are mixed with cheaper, more neutral-tasting oils. When shopping for oil, always stick with extra virgin — it may cost a bit more, but it’s well worth it.
Olive oil is sensitive to light and high temperatures, so purchase bottles that are darkly colored or opaque, which preserves its quality. Serious olive oil producers favor glass bottles over plastic, which are used for cheaper oils that should only be used for cooking. If you're looking for a nice bottle to use for salads or savoring, check the label for a harvest date; the best olive oil producers will always include that information somewhere on the bottle. Once it's opened, store your bottle of olive oil in a cool, dark place, and use within two months.