KINETIC DETERMINATION OF INHIBITION RATE CONSTANTS FOR NATURAL ANTIOXIDANTS IN LEMON ESSENTIAL AND BLACK SEED OILS USING A MODEL OXIDATION ASSAY

Essential oils (EOs) contain natural antioxidants that play a critical role in food preservation by preventing premature spoilage, rancidity, and decay. While data on EO antioxidants is plentiful, there remains a lack of precise methods for evaluating their efficacy. Kinetic analysis, in particular, offers deeper insight into activity constants and reaction mechanisms. This study utilizes the liquid-phase aerobic oxidation of cumene, initiated by benzoyl peroxide (BPO) at 343K, to determine the effective inhibition constants of antioxidants in commercial lemon essential oil (LEO) produced from fruits of Azerbaijan’s Lankaran zone and cold-pressed black seed oil (BSO). Prior to antioxidant analysis, PBO decomposition rate constant (kd) and created rate of initiation [Wi(0)] has been accurately determined at 343K to be 7.5• 10-6 (s-1) and 4•10-8 (Ms-1), respectively. Oxygen uptake was monitored via a gasometric setup. Results indicate that LEO significantly flattens the oxygen consumption curves, reducing the oxidation rate and introducing an induction period. The effective rate constant for LEO hydrogen donors was identified as k7(eff.) = (6.0 ±2.0) M−1s−1, likely due to oxygenated terpenes. However, the overall antioxidant capacity is primarily driven by alkyl radical (R•) scavengers. The total antioxidative activity (A) for LEO and BSO was measured to be 66.5% and 69.1%, respectively, aligning with existing literature