Effects of oxalic acid-chitosan compound treatment on quality and postharvest storage of mango

【Objective】 In order to provide theoretical basis and technical guidance for the storage and fresh-keeping of mango(Mangifera indica Linn) fruit, the effects of oxalic acid and chitosan on the quality and fresh-keeping of mango fruit were studied.【Method】 Tainong No.1 mango fruits were soaked in 1% chitosan for 5 min(CTS treatment), 5 mmol/L oxalic acid for 10 min(OA treatment), 5 mmol/L oxalic acid for 10 min and then soaked in 1% chitosan for 5 min(OACTS treatment), and soaking in clear water(control, CK), then dried and stored in a cold storage at 20℃. The effects of three preservation ways on the decay rate, hardness, soluble solids, titratable acid, total phenolics, flavonoids, anthocyanins and the activities of catalase(CAT), peroxidase(POD) and glutenin reductase(GR) were investigated.【Result】 During storage, the accumulation of anthocyanin was inhibited by OA and OA-CTS, and the peak value of anthocyanin was delayed for 4 d by OA-CTS. The accumulation of flavonoids was induced by OA and OA-CTS at the 5 thto 9 thd, the activities of CAT were increased by OA-CTS treatment by the 13 thd, and the activities of CAT were increased by CTS and OA-CTS treatments by day 5, day 13, day 21 and day 25. At the 21 stday, the hardness of CTS, OA and OA-CTS increased by 0.7, 2.1 and 1.2 kgf, while the soluble solid content of CTS, OA and OA-CTS decreased by 4.9%, 1.3% and 5.4%(absolute value, the same below), respectively, the titratable acid contents increased by 0.40%, 0.36% and 0.26%respectively, and the GR activity of CTS, OA and OA-CTS increased by 0.08, 0.10, 0.21 U/g. At the 25 thd, CTS and OA-CTS decreased the decay rate of mango by 0.5% and 0.8%, CTS, OA and OA-CTS decreased the solid-acid ratio by 51.50, 9.41 and 37.21, CTS and OA increased the CAT activity by 2.96 U/g and 15.87 U/g, the POD activity was increased by 2.50 and 3.97 U/g by OA and OA-CTS, and the polyphenol content was decreased by 0.03 U/g by OA.【Conclusion】 1% chitosan, 5 mmol/L oxalic acid and the compound treatment of oxalic acid-chitosan can maintain the sensory and nutritional quality of postharvest mango, improve the antioxidant ability and prolong the storage time of mango. These treatments can be applied in mango postharvest storage.