Oxidative Protection of Sunflower Oil Used in Industrial Process at High Temperature by Volatile Components from Origanum vulgare and Humulus lupulus Essential Oils

Lipid oxidation is the principal process of edible oil degradation. Therefore, the objective was to determine the antioxidant effect of hop and oregano essential oils in sunflower oil under high temperatures, in order to replace the synthetic antioxidants. The sunflower oil was enriched with oregano and hop essential oils (0.02% w/w). These treatments were compared with sunflower oil with the addition of BHT (0.02% w/w) and another sample of sunflower oil (without additives). All treatments were exposed to 150 °C for 8 h. Samples were collected at 0, 2, 4, 6, and 8 h. Peroxide value (PV), conjugated dienes, oxidation, and essential oils volatile compounds were measured. Oregano and hop essential oil increased the oxidative stability of the sunflower oil under 150 °C. The PV of the control was 44.1 meq O₂/kg at 8 h, while sunflower oil with the addition of hop and oregano essential oils were 14.4 meq O₂/kg and 8.5 meq O₂/kg at 8 h, respectively. Origanum vulgare essential oil had the best antioxidant effect, obtaining 80.7% less PV than the control, while Humulus lupulus showed 67.4% less PV than the control. In general, in comparison to the sunflower oil without additives, lower values of hexanal and 2-heptenal were observed in the samples enriched with essential oils. The principal components of these essential oils were found in the heated samples. Terpinen-4-ol (oregano) and β-myrcene (hop) were present at 4 h of the heat treatment. Thus, these terpenes appeared to be responsible for maintaining the antioxidant protection of sunflower oil throughout the heat treatment.