Evaluation of Sensorial Markers in Deep-Fried Extra Virgin Olive Oils: First Report on the Role of Hydroxytyrosol and Its Derivatives

Abstract

Extra virgin olive oil (EVOO) is one of the main daily food items consumed around the world, particularly in the Mediterranean region, and it has unique organoleptic properties. This study aims to determine the best frying conditions of EVOO supplemented with natural exogenous antioxidants enriched in hydroxytyrosol (HTyr) and its derivatives from olive fruit extract (OFE) to conserve its positive sensorial attributes while minimizing its sensorial defects, in particular, rancidity under high thermal processes. In this study, an experienced panel assessed the sensory attributes of nine EVOO varieties, olive oil 0.4° (mixed virgin olive oil (VOO) with refined olive oil (ROO)), Orujo olive oil, and olive oil 1° (EVOO mixed with ROO), compared with two sunflower oil types, performed using a deep-frying (D-F) process with numerous variables, i.e., frying time, frying temperature, and the addition of polyphenols enriched with HTyr. Results showed that most EVOO samples were stable under D-F at 170 °C for 3 h, with added polyphenols (∼650 mg/kg). Moreover, at these best values, the results stated that Arbequina, Picual, Royuella, Hojiblanca, Arbosana, and Manzanilla oils have low rancidity scores with values of 0, 1.7, 1.8, 2.3, 3.1, and 3.7, respectively, and stable/higher positive sensorial attributes, i.e., fruity, bitter, and pungent properties; however, olive oil 1° and olive oil 0.4° have high rancidity and low positive sensorial attributes. Notably, OFE helps maintain bitterness close to control in Picual, Koroneiki, Empeltre, and Arbosana oils. Furthermore, amongst the 19 tested sensory descriptors, only 8 descriptors—namely, fusty/muddy sediment, winey/vinegary/acid/sour, frostbitten olives (wet wood), rancid, fruity (green), fruity (ripe), bitter, and pungent—were successfully developed to allow characterization of the sensory quality of various olive oil categories under D-F. The present research confirmed that OFE may be used to provide stable EVOOs with higher positive sensorial qualities and lower defects and could be used as a natural antioxidant and promising strategy during the D-F process with EVOOs, not only for domestic practices but also at the industrial level.