Ethylene degradation via vacuum ultraviolet photolysis: nth-order kinetic model, energy consumption assessment, and a case study for 'Fuji' apples under retail conditions

Effective management of ethylene along the value chain is crucial to the regulation of fruit ripening and senescence to reduce postharvest losses. The objectives of this study were to, (i) investigate the degradation kinetics of ethylene using a vacuum ultraviolet (VUV) photolysis reactor at different light intensity (0.0005 mW/m², 0.0014 mW/m² and 0.0021 mW/m²) and relative humidity (RH) levels (20 % and 80 %), and (ii) evaluate the economic feasibility of the VUV photolysis system. Kinetic experiments were performed in batch mode with an initial ethylene concentration of 51 mg L⁻¹. The reaction order and rate constant were determined by employing an nth-order kinetic model. Light intensity and RH significantly influenced the kinetic parameters and ethylene degradation (p < 0.05). At low light intensity, ethylene degradation followed a zero-order kinetic model, while at high intensity, it followed a fractional-order kinetic model. The developed kinetic models accurately predicted the experimental concentrations (R² = 0.9955). The economic feasibility of the VUV photolysis system was assessed using electrical energy per order (E_EO), which remained below 10 kW m^-³ order⁻¹, indicating energy efficiency and practical applicability. The chamber equipped with the VUV reactor successfully preserved apple quality (maintaining low TSS/TA ratio and delaying pH increase) during storage for 28 d at 15°C compared to the control. This foundational application of VUV photolysis in ethylene degradation offers promising prospects of upscaling for long-term storage investigation and industry applications.