Deep Frying in Extra-Virgin Olive Oil: Evaluating the Influence of the Type of Food and Breading on the Degradation of Phenolic Compounds

Deep-frying in vegetable oils is a widespread practice around the world. The use of extra virgin olive oil (EVOO) for frying is supported by the presence of bioactive compounds such as phenols, which contribute to oxidative stability and are partially transferred to the fried food. We monitored by LC-MS/MS, the degradation of phenols in Picual and Arbequina EVOOs during consecutive frying cycles of different types of foods. The phenolic content decreased significantly (p-value <0.0001) in oils, but the decrease was more pronounced with nonbreaded foods (around 93% for chicken wings and anchovies) than with breaded foods, with a degradation between 70% and 78%. An exception was found for potatoes that behaved similarly to breaded foods, and this was attributed to their composition. Comparative analysis of the EVOOs revealed that secoiridoids primarily respond to oxidation during frying, but the aglycone isomers have a stronger protective capability than oleacein and oleocanthal.