Comparing Ultraviolet and Photocatalytic Disinfection Techniques and Their Synergistic Effects on Pesticide Presence and Quality Parameters in Grapes

The efficacy of ultraviolet (UV) and photocatalytic disinfection techniques, individually and synergistically, in degrading pesticide residues and maintaining quality parameters in grapes were investigated. A bench-scale photocatalytic reactor equipped with UV lamps and photocatalysts (TiO₂ and ZnO) was used for the treatments. LC-MS/MS was employed to check the presence and absence of pesticide residues after UV and photocatalyst treatments. UV-C treatment alone showed an absence of chlorpyrifos and cyprodinil pesticides, whereas UV-C with TiO₂ or ZnO led to near-complete degradation of all pesticides found in grapes. Quality assessments showed a reduction in total phenolic content (TPC) from 269.4 ± 36.2 to 239.7 ± 30.2 mg GAE/100 g with UV-C alone, whereas addition of TiO₂ improved TPC to 273.2 ± 18.3 mg GAE/100 g. Total flavonoid content (TFC) decreased significantly to 17.04 mg QE/100 g with UV-C, but less so with UV-B and UV-A. Ascorbic acid content dropped from 34.91 to 15.75 mg/L with UV-C, but UV-B and UV-A retained more ascorbic acid. Microbial analysis showed a reduction in total plate count from 6.30 ± 0.04 to 3.19 ± 0.10 log CFU/g with UV-C. Overall, the combined treatments of photocatalysts assisted with UV demonstrated an environmentally friendly method for enhancing grape safety and quality, presenting a viable alternative for postharvest disinfection.