Light olive oil does not contain fewer calories than other olive oils or, for that matter, any edible oils. As far as calories are concerned, an oil is an oil, all oils are fats, and all fats give us approximately 9 calories of energy per gram.
The word light is thrown around by food manufacturers to mean anything they want it to mean, including virtually nothing. In the case of olive oil, however, all you have to do is look at the bottle and you know that in this case it means light in color, and almost certainly in flavor.
We use vegetable oils in the kitchen mainly for sautéing, frying, and dressing salads. These functions are primarily physical rather than chemical in nature. In frying, for example, oil acts as an inert liquid that allows us to cook foods very quickly at a temperature much higher than that of boiling water. On salads, oil helps the dressing to stick; it “cuts” the acid; it carries other flavors, such as those of garlic and herbs; and it imparts unctuousness, a smooth, flowing mouth feel. These qualities are all largely physical, not chemical, and any relatively flavorless oil such as canola or corn oil can do those jobs.
Perhaps without realizing it, then, we may be tempted to think of kitchen oils in purely mechanical rather than flavor-related terms. As a result, many Americans prefer oils that are relatively tasteless, in fact, the blander the better, and colorless (or at most pale yellow). The olive oil producers oblige those customers by making a decolorized and deodorized version. They decolorize the oil, which is often not of top quality to begin with, by adsorping the colored substances onto a fine clay, and they deodorize it (odor being a big part of flavor) by treating with high-pressure steam, in much the same way in which seed oils are refined.
But that’s really a shame, because natural olive oils, ranging in color from yellow to gray-green, possess a remarkable diversity of rich flavors and aromas that cooks prize for various culinary uses. Unlike most other kitchen oils, olive oil contributes its own flavor to whatever is cooked in it or dressed with it. It is a flavor ingredient in itself, not just a medium for carrying other flavors. That’s why most Mediterranean cooking, which uses olive oil almost exclusively, is so flavorful. (The garlic also helps.)
The flavors of olive oils, like those of wines, vary with the country of origin, the variety of fruit (there are some fifty different species in general cultivation), the local soil and climate, how the groves are cultivated, when the olives are harvested, and how they are processed. The predominant flavor notes in olive oils include fruity, green, fatty, grassy, sweet, bitter. and astringent.
The chemistry of olive oils can be discussed from at least two standpoints: what are they made of in general, and what are their flavor and aroma compounds in particular? I won’t burden you with the polysyllabic names or formulas of all these chemicals, but I do want to point out a few of the ones that are of particular relevance to the qualities we value most highly in olive oils.
In view of the wide variation in olive oils, no exact analyses of their fatty acids can be stated, despite the supposedly exact figures quoted in many food publications. The oleic acid content, for example, can range anywhere from 55 to 83 percent. Nevertheless, some average values, not to be taken too literally. Not listed are about a dozen other fatty acids that are present in minor amounts.
When olives are crushed to express their oil, they release enzymes (lipoxygenases) that oxidize some of the polyunsaturated fatty acids to produce a wide variety of volatile aromatic compounds, including aldehydes, esters, and alcohols. More than one hundred volatile compounds have been identified in the olives’ aromas alone, and chemists know the details of how most of them are formed.
The acidities of olive oils, that is, the percentages of free oleic acid molecules broken off from fat molecules, have been much discussed. Acidity is easy to measure, and quality-control examiners have long used the degree of acidity, along with several other characteristics, as a gauge of quality. Supposedly, the more free acid, the harsher the flavor and the lower the quality. In the fall of 2003, the European Union reduced the maximum permitted acidity of EU produced extra-virgin olive oils from 1.0 to 0.8 percent. Nevertheless, it has recently been shown that acidity and flavor quality are not necessarily directly related to each other.
According to regulations of the EU and the International Olive Oil Council, here are the characteristics of the several grades of olive oil, in order of decreasing quality.
• Extra-virgin olive oil is virgin olive oil (see following grade) that meets strict composition and flavor characteristics. It’s the top o’ the heap. Obtained from perfect olives that have been crushed as soon as possible after harvest (their flavor deteriorates quickly) and processed without the use of heat or steam, extra-virgin oil exhibits the ideal flavor and aroma of its variety. It must contain less than 0.8 percent of free fatty acids. Extra-virgin oils are sometimes called “cold-pressed,” but that term is being phased out as pointless; olive oil presses don’t need to be cooled and are rarely, if ever, heated.
• Virgin olive oil must contain 100 percent olive oil from olives of one or more varieties. It must be obtained only by pressing, washing, decanting, centrifuging, and filtering, or certain other processes that do not alter its natural state. No additives, colorants, flavorings, or any other foreign matter may be added.
• Pure olive oil or 100% olive oil is virgin olive oil that has been blended with refined olive oil: oil that has been further processed with steam to remove off flavors and acids. But it still contains nothing but olive-derived ingredients.
• Light or extra-light olive oil is typically a blend of virgin and highly refined oils, most of whose colors, off flavors, and (for that matter) “on flavors” have been removed.
• Pomace oil: The oft-quoted statement that extra-virgin oils come from the “first pressing” of the olives is baloney. Olives are pressed only once. But more oil may later be extracted from the pressed pulp, skins, and stones (the pomace), which still contains some 4 to 10 percent oil. It can be extracted by a combination of pressure, heat, and chemical solvents, yielding what is called pomace oil, the bottom of the barrel in quality. You won’t even find it in most grocery stores.
Which brings us back to your question. (Remember your question?) By the time olive oil has been filtered, purified, decolorized, and practically de-olived to make light olive oil, most of its most flavorful, aromatic, and healthful compounds are gone. So rather than using an oil that has been stripped of its oliveness, be a sport and experiment with the wide variety of olive oils on the market until you find your one or two favorites. Choose based on one and only one criterion: what you like.
Some chefs and cooks believe it’s a waste of a good drinking wine to use it in cooking. Others say that if it’s not good enough to drink, it’s not good enough to cook with. Similarly, conflicting advice abounds on whether a good, extra-virgin olive oil is wasted by using it to sauté or fry. Except for deep-frying, I prefer extra-virgin oil, both in cooking and on the table.
For deep-frying in olive oil (Americans don’t do that very much, but Spaniards do), I use a good virgin oil. If you do too, try to find out from a specialty store or from the brand’s website the name of the predominant variety of olives that went into the oil. Spanish picual oil is reputed to be exceptionally stable at high frying temperatures.
Keep your olive oil ever within reach, but not too near the stove.
Heat deteriorates all cooking oils and olive oil in particular, because its high percentage of unsaturated fatty acids is more susceptible to oxidation than are the saturated fatty acids of many other vegetable oils.
Like heat, light too is an enemy of olive and other vegetable oils. That’s why most olive oil bottles are green or smoky colored. You’ve read a million times (including a few pages ago in this book) that you should keep oils in “a cool, dark place,” but there’s no need to go overboard. “Cool and dark” doesn’t mean inside a refrigerator whose door is never opened lest its interior light go on.
“Cool” is a relative term, best interpreted as “not warm.” Nor does “dark” mean pitch-black. The high-energy ultraviolet rays in sunlight are what do the damage, so by all means keep your oil out of direct sunshine. Incandescent lighting doesn’t contain enough ultraviolet light to worry about, unless your kitchen is as bright as an operating theater.
Fluorescent fixtures, however, do emit a substantial amount of ultraviolet light and should not be too near your oil dispensing station.
Note that almost 80 percent of the fatty acids in olive oil are monounsaturated and almost 10 percent are polyunsaturated. This high level of unsaturation has been linked to the healthful effects of olive oil. However, bear in mind the wide variation in types of olive oils. The percentage of saturated fatty acids in olive oils can range from 8 to 26, monounsaturated from 53 to 87, and polyunsaturated from 3 to 22.
Besides fats, olive oils contain other healthful chemicals in small amounts. Among the antioxidants are polyphenols; toco pherols, including vitamin E; and beta carotene, which manufactures vitamin A in the body.
The good-fat, bad-fat follies have been in continual ferment for the past few decades, so I won’t venture out onto any limbs that may crack off before you read this. Nevertheless, at this writing, it’s safe to say that saturated and trans fatty acids are the bad guys, while unsaturated (mainly monounsaturated) fatty acids are the good guys. Stay tuned.