Frying oil at high temperatures (approximately 180o C (356ºF) or over) is a widespread processing method used to prepare foods of vegetable and animal origin. Numerous factors influence the stability and performance of frying oil.
Edible oils are composed of triacylglycerols (>96%) and endogenous minor components, and at elevated temperatures, oils change significantly due to the many chemical and physical reactions which occur, such as oxidations, hydrolysis, cyclization, isomerization, and polymerization.
For example, when frying, oil also decomposes into volatile compounds that are capable of causing health problems due to their high content of free radicals, trans-fatty acids, conjugated linoleic acids, and some oxidized volatile products.
Frying is one of the oldest cooking procedures and is still among the most popular ones for food preparation. Due to their unique sensory characteristics, fried foods are consumed often and with pleasure.
During frying, part of the oil is absorbed by the food, thereby becoming part of our diet; most interestingly, in the Mediterranean area, approximately 50% of total fat intake is provided by cooking fats.
It was previously believed that extra virgin olive oil wasn’t good for frying due to its smoke point. But according to different studies, we now know that is as good and even better when compared to other oils because the smoke point does not predict the performance of the oil when heated, and oxidative stability and UV coefficients are better predictors. Of different oils tested, extra virgin olive oil (EVOO) has been shown to be the best one, even for frying.
Guillaume C., et al. “Evaluation of Chemical and Physical Changes in Different Commercial Oils during Heating”. Acta Scientific Nutritional Health 2.6 (2018): 02-11.
Antonia Chiou, Nick Kalogeropoulos. Virgin Olive Oil as Frying Oil. 2017. Comprehensive Reviews in Food Science and Food Safety. https://doi.org/10.1111/1541-4337.12268