Basil and Cinnamon Essential Oils Improve Oxidative Stability and Fatty Acid Composition of Vegetable Oil Blends During Deep-Frying

The present study evaluated the effects of basil essential oil (BEO) and cinnamon essential oil (CEO) on the oxidative stability and fatty acid degradation of vegetable oil blends during deep-frying. Three vegetable oil blends (OB1, OB2, and OB3), formulated with different n-6/n-3 fatty acid ratios, were supplemented with essential oils at concentrations of 200, 400, 800, and 1200 ppm and subjected to repeated deep-frying at 180 ± 5 °C for 8 h with periodic sampling. Changes in fatty acid composition, peroxide value (PV), acid value (AV), malondialdehyde (MDA), and p-anisidine value (AnV) were performed to characterize lipid oxidation under thermal stress. Prolonged frying significantly increased oxidation indices and accelerated the degradation of polyunsaturated fatty acids, particularly n-3 fatty acids, leading to an increased n-6/n-3 ratio. However, supplementation with basil and cinnamon essential oils effectively inhibited lipid oxidation and reduced fatty acid degradation compared with the control. Both essential oils decreased PV, AV, MDA, and AnV in a concentration-dependent manner, with more pronounced effects at 800 and 1200 ppm. Kinetic analysis showed that MDA formation followed a zero-order model, while PV changes fitted a first-order kinetic model, with R2 values ranging from 0.857 to 0.932. These findings suggest that basil and cinnamon essential oils enhance the oxidative stability of vegetable oil blends during deep-frying by reducing lipid oxidation and slowing unsaturated fatty acid degradation, highlighting their potential as natural antioxidants for frying oil applications.