Effects of Malic Acid Treatment on Quality and Active Oxygen Metabolism of Postharvest Apricot Fruits

In order to investigate the effects of exogenous malic acid (MA) on antioxidant metabolism and quality of postharvest apricot fruits, apricot 'Saimaiti' was used as experimental material. The apricot fruits were soaked in 5, 10 and 15 mmol/L MA for 10 min. The treated apricot fruits were stored at 0±1 ℃ and 90%~95% relative humidity for 49 days. The firmness, soluble solids content, titratable acid content, decay rate and antioxidant metabolism of apricot fruits were measured every 7 days. The results showed that MA treatment slowed down the decrease of hardness, titratable acid and total soluble solids contents. MA treatment with 10 mmol/L had the best effect. Further research showed that malic acid treatment significantly increased the activities of superoxide dismutase, catalase, peroxidase, ascorbate peroxidase and glutathione reductase during storage of apricot fruits. It decreased the production rate of superoxide anion radical and the content of hydrogen peroxide, inhibited the decrease of ascorbic acid, glutathione, total phenolics and flavonoids, and increased the content of malondialdehyde. The integrity of cell membrane was maintained for a long time. These results indicate that MA treatment is closely related to the maintenance of postharvest apricot fruit quality and its regulation of active oxygen metabolism.