The question of how safe a specific type of oil is for high-temperature cooking has long been somewhat murky. Particularly the issues surrounding olive oil and frying have in recent years been associated with a lot of uncertainty and questions. This is primarily due to the fact that previous studies have shown that prolonged frying in olive oil could cause both harmful oxidation and result in the development of toxic by-products called polar compounds that have been linked to the development of serious health problems including Alzheimer’s and Parkinson’s diseases.
A New Study
Recent Australian research published in May 2018, however, shows that if you choose a really good extra virgin olive oil it can actually withstand even longer-lasting heating and frying.
These researchers analyzed a number of cooking oils, including coconut oil, canola oil, sunflower oil, grapeseed oil, peanut oil, rice oil, avocado oil, olive oil, virgin olive oil and extra virgin olive oil. Results showed that extra-virgin olive oil was the safest and most stable when heated to temperatures even higher than those commonly used for sautéing, deep-frying, and baking. It produced the lowest quantity of polar compounds compared to the other oils tested. The runner up was coconut oil.
On the other hand, refined oils such as canola oil, sunflower oil, and grape seed oil fared poorly and therefore cannot be recommended for frying or indeed any kind of heating.
This therefore also means that canola oil isn’t as healthy as commonly thought, even though, like olive oil, it has a high content of monounsaturated fat. The researchers reported that canola oil was the most unstable of all the oils tested, producing more than 2.5 times the amount of polar compounds of extra virgin olive oil and about twice that in heated refined olive oil.
The study also disproved the commonly held view that oil with a high smoke point is best suited for high-temperature cooking. In fact, an oil’s smoke point doesn’t indicate how it will perform when heated.
The analysis was performed in an ISO17025 accredited laboratory. The oils in the experiments were heated to 150, 180, 210 and 240 degrees centigrade respectively, for 20 minutes. In addition, three liters of oil were heated up to 180 degrees in a deep fryer. Then samples were taken after 30, 60, 180 and 360 minutes, respectively.
In the above experiment, the samples were cooled down to 25 degrees and then analyzed. It was tested for smoking point, by-products, trans-fatty acids, free fatty acids, fatty acid profile and oil stability index, among others.
The Take Away?
From this study, it seems that quality does pays off. We know that olive oil has a very high percentage of heart-healthy monounsaturated fat. High quality olive oil also contains abundant antioxidants, substances that have been shown to have protective cardiovascular and anti-cancer effects. And it provides oleocanthal, a unique anti-inflammatory compound. And, of course, quality olive oil tastes great. We now know it is also the safest oil for sautéing and other high-temperature cooking. Personally I think this is great news.
Learn more about how to choose the best olive oil in my article How to choose the best olive oil.
If you would like to read the original Australian study please follow this link.