橄榄油素有“液体黄金”之称。橄榄油当中含有较高的单不饱和脂肪酸（55~83%），即油酸。这种物质除了供给人体所需的大量热能外，还能调整人体血浆中高、低密度脂蛋白胆固醇的浓度比例。其中的亚油酸和亚麻油酸为人体所必需，但人体不能自身合成，食用过量对人体也有害。橄榄油中所含油酸、亚油酸和亚麻油酸的比例正好是人体所需的比例，类似母乳，这也是其他植物油所不具备的。同时橄榄油富含丰富的维生素A、D、E、F、K成分和胡萝卜素等脂溶性维生素及抗氧化物等，极易被人体消化吸收。而且橄榄油不含胆固醇，对健康更加有益。
根据加工方法不同，橄榄油分为初榨和精炼两大类，营养成分上也有所区别。初榨橄榄油是直接从新鲜的油橄榄果实中采取机械冷榨的方法榨取，经过过滤等处理除去异物后得到的油汁，加工过程中完全不经化学处理。此类橄榄油质量最佳，具有独特香味，金黄色中带有绿色，口感丰富，相当于一种果汁，可以直接食用或用于凉拌、沙拉，突显原汁原味。精炼橄榄油是通过采用溶解的方法从冷榨后的油渣中提取的橄榄油。在通过脱色、除味等提炼过程后，其酸性值一般可降低到0.3%以下，虽然营养价值不如初榨的，但味道也不错，价格较为平民化，而且油酸含量仍高于其他品种的油。
正因如此，在强势的宣传下橄榄油成了不少家庭的新宠。但在东西方巨大的文化差异下，橄榄油真能替代“大油”成为中国式烹饪的主角吗？
西方世界的日常饮食中很少炒菜，而研究证明橄榄油在高温下营养成分会遭到严重破坏。其一，橄榄油中的微量物质属多酚类，在高温环境下容易被破坏，降低其营养特性。其二，单不饱和脂肪加热到冒烟后，容易变成不健康的反式脂肪，而反式脂肪已被证实是一种高致癌物。而橄榄油的冒烟温度比花生油之类的要低很多，基本上只要一炒菜，就会产生反式脂肪。
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.
