Gaseous ozone extends shelf life of high-moisture white onions

Gaseous ozone is widely recognized for its antimicrobial capabilities and may offer an effective solution to reduce postharvest losses in high-moisture onions, which are especially vulnerable to deterioration during ambient storage. The study investigated how ozone treatment applied during postharvest drying affected decay, microbial contamination, and physicochemical quality in ‘Cipolla Bianca di Margherita di Savoia’ onions.

After harvest, the onion bulbs were exposed to 0.5 ppm gaseous ozone for 17 hours at 30 °C and for 17, 24, 36, or 48 hours at 20 °C. Untreated onions served as control samples at each temperature condition. Following treatment, all samples were stored at 20 °C with 65 % relative humidity and assessed after 9, 16, and 23 days.

Researchers evaluated visible defects, microbial populations, color, firmness, moisture levels, dry matter, total soluble solids, phenolic compounds, and antioxidant activity. The findings revealed that onions treated for 17 hours at 30 °C and those treated for 48 hours at 20 °C showed the lowest decay incidence and reduced mesophilic bacteria and mold counts after 16 and 23 days of storage.

After 23 days, black decay affected only around 5 % of the treated onions, whereas untreated samples recorded decay levels between 20 % and 24 %. Importantly, ozone exposure caused no negative changes in color, firmness, moisture content, soluble solids, total phenols, or antioxidant activity. According to the study, applying gaseous ozone during the drying process improves the storage stability of high-moisture onions kept at room temperature.

Source

Fathi-Najafabadi, A., Castillejo, N., Fatchurrahman, D., Amodio, M. L., & Colelli, G. (2026). Gaseous ozone treatment increases postharvest shelf-life of high-moisture white onions. ScienceDirect