Temporal spatial profiling of reactive oxygen species metabolic dynamics in cold plasma-treated paddy rice during postharvest storage

Paddy rice is prone to quality deterioration during storage due to imbalances in reactive oxygen species (ROS) metabolism under high-temperature and high-humidity conditions. In this work, the optimized procedure by dielectric barrier discharge cold plasma (DBD-CP) was applied to paddy rice grains, and stored at 35 °C for 60 days. The regulation of ROS metabolism and the significance of various storage quality indicators were evaluated. In the results, DBD-CP treatment significantly reduced respiration intensity, with a maximum decrease of 84.21% (P < 0.05) during storage period. Malondialdehyde (MDA) content showed a significant decline from day 20 onward (P < 0.05). ROS quantification revealed an 18.15% reduction at 30 days, while levels of specific ROS species O2−∙, H2O2, and HO· decreased by 41.86% (day 40), 43.72% (day 60), and 57.48% (day 50), respectively, alleviating oxidative stress. Antioxidant responses were enhanced, with total phenolic content (TPC) and total flavonoid content (TFC), as well as overall antioxidant capacity, significantly increased (P < 0.05). Enzyme activity analysis indicated that ascorbate peroxidase (APX) activity increased by 29.11%, while peroxidase (POD) activity decreased by 47.37%, reducing oxidative depletion of phenolics, limiting excessive ROS accumulation. The temporal and spatial distribution of ROS during storage was visualized and statistically analyzed using a confocal laser scanning microscope (CLSM). The results showed that DBD-CP treatment effectively suppressed the burst of ROS during rice storage, significantly reduced its fluorescence signal intensity, and maintained its stability. Overall, DBD-CP treatment effectively modulated both enzymatic and non-enzymatic antioxidant mechanisms, significantly reducing ROS levels and improving the storage quality of paddy rice grains.