Effects of Low-Temperature Plasma-Activated Water (PAW) on Cold Sterilization Efficacy and Storage Quality of (Prunus persica (L.) Batsch)

Plasma-activated water (PAW) is an emerging non-thermal sanitization technology with potential applications in postharvest preservation. In this study, nine PAW treatments, generated by varying discharge voltage, O2 flow rate, and activation time, were first evaluated for their effects on surface microbial counts, rot incidence, weight loss, and fruit firmness in stored peaches (Prunus persica (L.) Batsch). Compared with untreated control, all PAW treatments significantly inhibited the proliferation of surface microorganisms and delayed rot development. Fruits treated with PAW exhibited reduced weight loss and retarded softening. Among these treatments, T9 (8 kV, O2 flow rate 12 mL/min, activation time 30 min; pH 4.28, EC 42.83 μS·cm−1) achieved the best comprehensive performance across the measured indicators and was selected for further analysis. Total soluble solids (TSS) content on a fresh-weight basis was significantly lower in T9-treated fruit at day 4 but higher on days 16 and 20 compared with the control, while titratable acidity (TA) showed no significant difference throughout storage. Physiological and biochemical analyses showed that T9 treatment modulated ROS homeostasis, reduced H2O2 and MDA accumulation, and altered the rise-and-decline dynamics of O2•−, accompanied by enhanced antioxidant enzyme activities (SOD, POD, CAT, and APX) at several storage time-points and changes in PAL activity during storage. Total phenolic content and DPPH radical-scavenging capacity were higher in T9-treated fruit, while PAL activity differed significantly from the control only on days 8 and 20. Untargeted metabolomic analysis of fruit collected on days 0, 4, 12, and 20 revealed time-dependent changes in phenylpropanoid, flavonoid, and amino acid metabolism. Overall, PAW treatment may delay postharvest quality deterioration and decay in peach fruits, possibly through a combination of reducing surface microbial loads and modulating antioxidant and phenylpropanoid metabolism. These findings provide a basis for PAW application as a residue-free preservation technology.