橄欖油素有“液體黃金”之稱。橄欖油當中含有較高的單不飽和脂肪酸（55~83%），即油酸。這種物質除了供給人體所需的大量熱能外，還能調整人體血漿中高、低密度脂蛋白膽固醇的濃度比例。其中的亞油酸和亞麻油酸為人體所必需，但人體不能自身合成，食用過量對人體也有害。橄欖油中所含油酸、亞油酸和亞麻油酸的比例正好是人體所需的比例，類似母乳，這也是其他植物油所不具備的。同時橄欖油富含豐富的維生素A、D、E、F、K成分和胡蘿卜素等脂溶性維生素及抗氧化物等，極易被人體消化吸收。而且橄欖油不含膽固醇，對健康更加有益。
根據加工方法不同，橄欖油分為初榨和精煉兩大類，營養成分上也有所區別。初榨橄欖油是直接從新鮮的油橄欖果實中采取機械冷榨的方法榨取，經過過濾等處理除去異物後得到的油汁，加工過程中完全不經化學處理。此類橄欖油質量最佳，具有獨特香味，金黃色中帶有綠色，口感豐富，相當於一種果汁，可以直接食用或用於涼拌、沙拉，突顯原汁原味。精煉橄欖油是通過采用溶解的方法從冷榨後的油渣中提取的橄欖油。在通過脫色、除味等提煉過程後，其酸性值一般可降低到0.3%以下，雖然營養價值不如初榨的，但味道也不錯，價格較為平民化，而且油酸含量仍高於其他品種的油。
正因如此，在強勢的宣傳下橄欖油成了不少家庭的新寵。但在東西方巨大的文化差異下，橄欖油真能替代“大油”成為中國式烹飪的主角嗎？
西方世界的日常飲食中很少炒菜，而研究證明橄欖油在高溫下營養成分會遭到嚴重破壞。其一，橄欖油中的微量物質屬多酚類，在高溫環境下容易被破壞，降低其營養特性。其二，單不飽和脂肪加熱到冒煙後，容易變成不健康的反式脂肪，而反式脂肪已被證實是一種高致癌物。而橄欖油的冒煙溫度比花生油之類的要低很多，基本上隻要一炒菜，就會產生反式脂肪。
Is it OK to cook with extra-virgin olive oil?
From: http://www.whfoods.com/genpage.php?tname=george&dbid=56
One of the main things to consider when evaluating whether it is OK to heat extra-virgin olive oil (or any other oil for that matter) is the smoke point of the oil. The smoke point is the temperature at which visible gaseous vapor from the heating of oil becomes evident. It is traditionally used as a marker for when decomposition of oil begins to take place. Since decomposition incurs chemical changes that may not only result in reduced flavor and nutritional value but also the generation of harmful cancer causing compounds (oxygen radicals) that are harmful to your health, it is important to not heat oil past its smoke point. Inhaling the vapors can also be damaging.
Oils and their smoke point
The smoke point is a natural property of unrefined oils, reflecting their chemical composition. When oil is refined, the process increases the oil's smoke point; in fact, raising the smoke point is one of the reasons why the refining process is used. To get a better idea of how refining increases the smoke point of oil, look at Table 1 that shows several examples.
Table 1
| Oil type | Smoke point |
|---|---|
| Canola oil, unrefined | 225°F |
| Canola oil, semirefined | 350°F |
| Canola oil, refined | 400°F |
| Safflower oil, unrefined | 225°F |
| Safflower oil, semirefined | 320°F |
| Safflower oil, refined | 450°F |
| Soy oil, unrefined | 320°F |
| Soy oil, semirefined | 350°F |
| Soy oil, refined | 450°F |
| Sunflower oil, unrefined | 225°F |
| Sunflower oil, semirefined | 450°F |
| Sunflower oil, refined high-oleic | 450°F |
Olive oil and its smoke point
Before I discuss the specifics of the smoke point of olive oil, I want to clarify some terms used to define olive oils since these terms are often a source of confusion for many people:
- Extra-virgin: derived from the first pressing of the olives (has the most delicate flavor).
- Fine virgin: created from the second pressing of the olives.
- Refined oil: unlike extra-virgin and fine virgin olive oils, which only use mechanical means to press the oil, refined oil is created by using chemicals to extract the oil from the olives.
- Pure oil: a bit of a misnomer, it indicates oil that is a blend of refined and virgin olive oils.
Now, unlike the information presented in Table 1, the information on olive oil smoke points is, unfortunately, not very clear or consistent since different companies list different smoke points for their olive oil products; this variability most likely reflects differences in degree of processing. Generally, the smoke point of olive oil ranges from 220-437°F. Most commercial producers list their pure olive smoke points in the range of 425-450°F while "light" olive oil products (which have undergone more processing) are listed at 468°F. Manufacturers of extra virgin oil list their smoke points in a range that starts "just under 200°F" and that extends all the way up to 406°F. Again, the variability here is great, and most likely reflects differences in the degree of processing.
Practical tips
In principle, organic, unrefined, cold-pressed extra virgin olive oil should have the lowest smoke point of all forms of olive oil since this form of the oil is the least refined, most nutrient dense and contains the largest concentration of fragile nutritive components. Oxidation of nourishing substances found in extra virgin olive oil, as well as acrylamide formation, can occur at cooking temperatures very closer to the 300°F/148°C range. For these reasons, I don't recommend cooking with extra virgin olive oil.
