An Australian team of researchers has found that extra virgin olive oil produced the lowest amount of toxic compounds in high cooking temperatures when compared with other vegetable oils and fats.

In the study, a team from the Modern Olives Laboratory Services heated a range of commonly used cooking oils and performed a range of tests to assess their stability after exposure to high temperatures.

The tested oils included extra virgin (EVOO), virgin (VOO) and refined olive oil, grapeseed, avocado, coconut, sunflower, rice bran, peanut and canola oils. They were heated for six hours at 180°C and in temperatures increasing from 25°C to 240°C over 20 minutes.

“When frying, oil decomposes into a variety of volatile compounds and monomeric and polymeric products, which are capable of influencing not only the sensory and health quality, but also the shelf life of the fried product,” the study said.

Some of the compounds were responsible for the pleasant taste and crispiness of fried goods, but others – including polar compounds – reduced the quality and shelf life of the oil and were linked to medical conditions such as Alzheimer’s disease.

The results revealed that EVOO developed the lowest amount of polar compounds after heating, closely followed by coconut and peanut oils, while the highest amounts of polar compounds were found in grapeseed and canola oils.

Additionally, the results suggested that – against popular conception – the smoke point of oils were not a relevant factor when determining their behaviour when heated, although the researchers found that a higher smoke point did result in more polar compounds being produced during heating.

Instead, the level of unsaturated fats, oxidative stability and UV coefficients were more accurate factors in predicting how the oils would degrade during heating.