Citrus Flavored Vegetable Oil: Oxidative Stability and Volatile Organic Compounds under Thermal Treatment

Lipid oxidation during heating degrades essential fatty acids in vegetable oils, generating off-flavors and potentially toxic compounds. Citrus, known for its natural antioxidant properties, may enhance oil stability under heat. This study evaluated physicochemical properties, pigment content, and volatile organic compounds (VOCs) of citrus-flavored vegetable oils (CFVOs) prepared using nasnaran, key lime, and kaffir lime in coconut, palm, and sesame oils. CFVOs were heated at 100, 120, and 140°C for 2 h, and oxidation was assessed through free fatty acid (FFA), acidity value (AV), and peroxide value (PV). Pigments (carotenoids and chlorophylls) were measured, and VOCs were analyzed by GC-MS with principal component analysis (PCA) and hierarchical cluster analysis (HCA). Citrus addition reduced oxidation markers compared with controls. At 140°C, control coconut oil reached FFA 0.284% and PV 2.100 meq/kg O₂, whereas CFVOs showed lower levels (e.g., FFA 0.255% and PV 0.867–0.833 meq/kg O₂). Citrus incorporation increased carotenoids and chlorophylls; carotenoids rose from 0.272 mg/kg (control) to 1.477 mg/kg in nasnaran-flavored oil, while chlorophylls increased from 0.763 mg/kg to 4.744 mg/kg. Heating reduced pigments, with carotenoids declining to 0.781 mg/kg and chlorophylls to 3.311 mg/kg at 140°C. VOC profiles showed temperature-dependent changes, and multivariate analyses distinguished samples by citrus type and oil matrix. Pigments correlated positively with monoterpenes and negatively with oxidation indicators. Overall, citrus incorporation improved thermal stability and aromatic complexity of vegetable oils, supporting its potential as a natural additive for enhancing oil quality during thermal processing.