Gaseous ozone treatment increases postharvest shelf-life of high-moisture white onions

Gaseous ozone is known for its antimicrobial properties and may reduce postharvest losses in onion bulbs, particularly in high-moisture onions with limited ambient storage stability. This study evaluated the effect of gaseous ozone applied during postharvest drying on decay, microbial load, and physicochemical quality of ‘Cipolla Bianca di Margherita di Savoia’ bulbs. After harvest, the onions were exposed to a gaseous ozone concentration of 0.5 ppm for 17 h at 30 °C and for 17, 24, 36, or 48 h at 20 °C. Non-treated samples were used as a control (CTRL) for each temperature. After treatment, all samples were stored at 20 °C with 65% relative humidity and evaluated after 9, 16, and 23 d. On each sampling day, defects, microbial content, color, firmness, moisture content, dry mass, total soluble solids, total phenols and antioxidant activity were evaluated. The results showed that after 16 and 23 d of storage, the onions treated at 30 °C for 17 h and onions treated at 20 °C for 48 h demonstrated the least incidence of decay and the lowest mesophilic and mold loads. The black decay incidence for onions treated for 17 h at 30 °C and for 48 h at 20 °C after 23 d of storage was around 5 %, whereas for untreated onions it reached 20-24 %. No detrimental effects on color, firmness, moisture content, soluble solids, phenols, or antioxidant activity were observed, indicating that gaseous ozone applied during drying enhances the storage stability of high-moisture onions at ambient temperature.