The effect of short-term gaseous ozone treatment on physical attributes and senescence-related enzymes of ‘Eureka’ lemons during cold sterilization

Abstract

Due to restrictions on the use of synthetic fungicides on fresh produce, there is growing interest in residue-free technologies such as ozone (O3), which may enhance fruit defence mechanisms against postharvest disorders. This study examined the effect of gaseous O3 on oxidative stress–related defence enzymes and the physical quality attributes of ‘Eureka’ lemons during cold sterilization. Fruit was exposed to 0.3 mg/L ozone for 24 or 48 h, then stored at 0 °C as the recommended temperature for sterilisation and 95% RH for 28 d, followed by 7 d at ambient temperature. Physicochemical variables, including colour, firmness, lipid peroxidation, catalase (CAT), glutathione reductase (GR), peroxidase (POD) and lipoxygenase (LOX) were assessed bi-weekly. Ozone treatments (48 h and 24 h) exhibited higher decay incidence between day 28 and 35 by 4% and 3.2%, respectively, compared to 0.91% in the untreated fruit. Although the O3 (48 h) treatment showed higher decay (p < 0.001), it had slightly better colour and firmness at the end of the assessment period. Gaseous O3 significantly increased CAT, LOX, POD, and GR (p < 0.001) from 0 to 28 days. A slight decline in CAT and GR was observed during ambient storage, particularly under O3 (48 h). Overall, these results suggest that O3 may exacerbate senescence traits of ‘Eureka’ lemons, and its use may compromise fruit quality and promote decay, particularly during cold sterilization. Considering that CAT and GR were significantly increased, further research should explore the shorter O3 durations and their impact on decay-causing pathogens and senescence-linked enzymes, specifically POD and LOX, to enhance the efficacy and safety of ozone as a postharvest treatment for citrus fruit.