Effects of Oxalic Acid Treatment on Quality and Antioxidant Metabolism of Postharvest Fengtang Plum Fruit

In order to explore the effect of oxalic acid (OA) treatment on the preservation of fruit and analyzed the preservation mechanism from the perspective of antioxidant metabolism, Fengtang plum fruit was chosen as the experiment material, and treated with 0 mmol/L (control) and 0.5 mmol/L oxalic acid for 10 min, dried and stored at room temperature of (25±1) ℃, and the changes of fruit quality, antioxidant substance and activity of antioxidant metabolism-related enzyme were measured. The results showed that 0.5 mmol/L oxalic acid treatment effectively delayed the increase of weight loss rate, decay rate and respiration rate, delayed the arrival of fruit respiration peak during storage, inhibited the increase of solid-acid ratio, soluble sugar content, malondialdehyde (MDA) content and superoxide anion (\rm O_2^-\cdot ) level of Fengtang plum fruit, and also inhibited the decrease of fruit firmness, titratable acid (TA), chlorophyll content, vitamin C (V_C) content, glutathione (GSH) content, ascorbate peroxidase (APX) activity, catalase (CAT) activity and superoxide dismutase (SOD) activity decreased of Fengtang plum. At the same time, oxalic acid treatment maintained a high level of soluble solids content (SSC). However, the effect of oxalic acid treatment in the experiment on the soluble protein content and peroxidase (POD) activity was not obvious. Through a comprehensive analysis of various indicators, it is concluded that 0.5 mmol/L oxalic acid treatment can delay the ripening and senescence of Fengtang plum fruit after harvest, enhance its antioxidant capacity, and inhibit the fruit quality decreased during postharvest storage at room temperature.