Application of ultrasound-assisted atomized plasma-activated water to improve the quality properties of grapes

Immersion washing disinfects microorganisms but requires drying before packaging and can detach grapes. Ultrasonic atomization generates mist and addresses these limitations. Plasma-activated water, a novel non-thermal technology, remains unexplored in atomization mode. This study applied atomized PAW to treat grapes, observing quality attributes during storage (day 0-7) at room temperature. Attributes included physicochemical properties (weight loss, decay incidence, firmness, titratable acidity (TA), total soluble solids (TSS)), microbial quality (counts of aerobic mesophilic bacteria (AMC), molds, and yeasts (M&Y); microbial community composition), markers of reactive oxygen species (levels of malondialdehyde (MDA), H₂O₂, and O₂^-), and physiological responses related to oxidative stress (activities of superoxide dismutase (SOD), catalase (CAT), phenylalanine ammonia-lyase (PAL), and chalcone isomerase (CHI)). Results showed PAW had minimal effect on TAA and TSS, while reducing decay and weight loss and maintaining greater firmness versus controls. PAW treatment stimulated SOD, CAT, PAL, and CHI activities, reducing MDA, H₂O₂, and O₂^- levels, indicating PAW mitigates oxidative damage. Microbial analysis showed PAW maintained lower AMC and M&Y counts during storage compared to controls. Gene sequencing revealed Aspergillus abundance increased with storage time, becoming dominant on days 4 and 7; however, PAW treatment maintained lower Aspergillus abundance than controls, reducing decay risk. After PAW treatment, Glomerella and Geosmithia showed less fluctuation during storage versus controls, with Glomerella maintaining highest abundance throughout. This suggests PAW may inhibit Aspergillus through microbial interactions by stabilizing Glomerella and Geosmithia abundance. This study confirms atomized PAW enhances grape quality during storage, supporting reduction of post-harvest losses.