Olive oil extraction can be traced back to as early as 4500 BC so we have a long history of its use in agriculture, and cooking. Due to its abundance, easy access and the good press on its health benefits (reducing the risk of heart disease, and possibly certain cancers, diabetes and Alzheimers), just about everyone has a bottle of olive oil in their cupboard. Most people assume it to be good for cooking. To test this out, I did my own kitchen experiment, which is laid out below. But first, a little background on why it matters.
All oils are sensitive to heat, oxygen and light to varying degrees - dependent on their growing conditions, processing, storage and fatty acid make-up. Exposure to too much heat, especially when an oil is repeatedly heated, can catalyze the formation of the cancer-causing, cell mutating and hormone disrupting PAH's (polycyclic aromatic hydrocarbons). Too much light or exposure to air generates oxidation and free radicals that contribute to all degenerative diseases.
In the case of olive oil, its tolerance to heat is somewhere between 275 - 410ºF, with most extra virgins averaging 375ºF. As mentioned above, the differences are determined by the olive varietal, growing conditions, fatty acid composition, the process used to extract it, storage conditions, and who you ask. If you heat olive oil higher than its tolerance, precious plant phenols and the Vitamin E are destroyed. Both polyphenols and Vitamin E have been identified as the main benefactors to heart health. Overheating, not only minimizes the nourishment, but it leads to the formation of the potentially problematic PAH's. To be clear, it is unlikely that occasional exposure the PAH's will cause much harm, as our detoxification system lead by our stalwart liver is equipped to handle a reasonable load. However we all need to be conscious of consistent and accumulated exposure. We have far less control over the the PAH's that are floating around our environment due to the fumes from vehicle exhaust, asphalt, coal combustion, wood-burning fires, agricultural burning and hazardous waste sites. However where we can exert more control is by minimizing exposure to PAH's from cigarette and tobacco smoke, eating grilled and charred meat or other grilled foods, consuming non-organic foods grown in contaminated soils and processed foods, and yes, by not overheating oils.
All this to say that heating olive oil too high, is of itself, not likely to cause harm - but where we can take control, we must do what we can to keep the PAH's at bay.
Using olive oil for cooking is not a free for all - fry at will, whatever and however long you want. Not if you want to give yourself all the opportunities that you can to be healthy.
With all this in mind, I wondered how long I could be sauteing/frying my food before the oil would heat beyond its capacity. So here is my kitchen experiment.
I used four different frying pans:
- ceramic non-stick (Green Earth Frying pan by Ozeri)
- stainless steel Lagostina
- non-stick Caphalon
- cast iron pan.
Along with a grill thermometer and a bottle of organic extra virgin olive oil by Emile Noel, I determined the time it took for the pan to reach various temperatures. I made the assumption that if the surface of the pan was at a particular temperature, then the oil right next to the thermometer would be at the same or a similar temperature. We have a gas stove and I kept it on medium-high heat (3rd mark from the highest), which I would most commonly use for sautéing vegetables. The table below shows the results.
Ceramic Green PanStainless SteelCalphalon Non-stickCast Iron
300 2:52stopped due to
After the green ceramic pan had cooled, I tested heating the olive oil on medium heat for ten minutes and the temperature never went above 310ºF, so the oil never smoked. I then turned it up to high heat and it smoked at 1 minute, 15 seconds.
Here are the conclusions that I drew from my little kitchen experiment:
- The pan that is used will determine how long an oil can withstand cooking. The ceramic green pan won out over all the others with the solid advantage of being an even and reliable conductor of heat without ever reaching too-high a heat (while being left on medium). Note however, that all the pans were older than the ceramic one. Age may play a part in the efficiency and heat conduction of a pan.
- Reheating is known to cause quicker breakdown of an oil. This was confirmed by my experiment of initially using medium heat and then shifting to high heat.
- It appears that we can use a high quality extra virgin olive oil for sautéing in most pans, as long as we keep it to medium heat and cook it for less than 4 minutes. In a ceramic pan we likely have the option of longer cooking times.
Buy your extra virgin olive oils in dark glass bottles to ensure that there isn't any unnecessary exposure to light. Cap the bottles as soon as you complete your pour. Cook on medium-high heat for limited amounts of time, dependent on the pan that you're using (generally less than 4 minutes) or low to medium heat for longer times to ensure that you optimize olive oils health gifts.
Pellegrini N, Visioli F, Buratti S, et al. Direct analysis of total antioxidant activity of olive oil and studies on the influence of heating. J Agric Food Chem 2001 May;49(5):2532-8.
Vissers MN, Zock PL, Katan MB. Bioavailability and antioxidant effects of olive oil phenols in humans: a review. Eur J Clin Nutr 2004 Jun;58(6):955-65.