Abstract: In order to study the effect of cold plasma treatment on the reactive oxygen species (ROS) metabolism and quality of postharvest daylily, fresh daylily flower buds were treated with dielectric barrier discharge cold plasma at 110 kV and 110 Hz for 150 s, and then stored for up to 15 days at (4 ± 1) ℃. The antioxidant enzyme activities in the treated samples were detected, and ROS metabolism levels and quality parameters were analyzed during the storage period. The results showed that compared with the control group, cold plasma treatment was able to induce superoxide dismutase (SOD) activity during the early stage of stage, significantly increase catalase (CAT) and peroxidase (POD) activity (P < 0.05), and inhibit the accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA) content (P < 0.05). Moreover, it significantly delayed the increase in cell membrane permeability (P < 0.05) and the hydrolysis of soluble protein, maintained the soluble solid content, and significantly inhibited the decrease in vitamin C (VC) content and the increase in a* value during the late storage period (P < 0.05), thus delaying the browning process. Therefore, cold plasma treatment can effectively slow down the postharvest metabolic activities of daylily, thereby maintaining its quality and extending its shelf life.

Key words: cold plasma; daylily; reactive oxygen species metabolism; low-field nuclear magnetic resonance