The impact of ultraviolet-C and ozone treatment on the pineapple fruit quality and the critical regulating factors...

Pineapple (Ananas comosus (L.) Merr.) faces significant postharvest losses due to rapid senescence and browning. While conventional cold storage and chemical treatments are commonly employed, they often entail risks of chilling injury and chemical residues. Ultraviolet-C (UV-C) is a proven non-thermal hormetic treatment, its mechanisms in pineapple remain unclear. This study investigated the synergistic effects of UV-C radiation and ozone treatment on the postharvest quality of pineapple. Results demonstrated that a combined treatment of 16 min (26.24 kJ m^-2 UV-C + 7.14 mL m^-3 ozone) significantly suppressed the accumulation of hydrogen peroxide (H₂O₂), superoxide radicals (O₂^-), and malondialdehyde (MDA). This was accompanied by enhanced antioxidant enzyme activities [superoxide dismutase (SOD) and catalase (CAT)] and elevated levels of non-enzymatic antioxidants (ascorbic acid and total antioxidant capacity), which collectively mitigated oxidative damage and delayed fruit senescence. Furthermore, UV-C and ozone treatment inhibited the activities of browning-related enzymes [peroxidase (POD) and polyphenol oxidase (PPO)] as well as cell wall-degrading enzymes [polygalacturonase (PG) and pectate lyase (PL)], thereby preserving cell wall integrity and retarding fruit softening. Metabolomic analysis showed that UV-C substantially reshaped polyphenol accumulation patterns and enhanced polyphenol compounds such as Dihydrobenzoic acid pentose, Pelargonidin-3-O-(6"-O-malonyl) glucoside, Methyl 4-Hydroxyphenylacetate, Sanguisorbin E. Transcriptomic profiling revealed that UV-C predominantly modulated genes involved in plant-pathogen interactions, MAPK signaling, and starch and sucrose metabolism-pathways critical for regulating antioxidant defense and cell wall remodeling. Weighted gene co-expression network analysis (WGCNA) further identified WRKY and bHLH transcription factors as hub regulators potentially coordinating ROS scavenging and MAPK-mediated stress responses. These findings elucidate the molecular mechanisms by which UV-C combined with ozone modulates postharvest physiology and provide a theoretical framework for implementing UV-C as a sustainable preservation strategy for pineapples.