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.
|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.
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.