Effects of combined treatment of 1-MCP and chitosan coating on the storability of Shengzhou Nane (Prunus salicina var. taoxingli) fruit

Abstract: 【Objective】Browning and decay of fruits shorten storage life and thus reduce their market value. 1-methylcyclopropene (1-MCP), an inhibitor of ethylene action, is effective at very low concentrationsin delaying fruit ripening and improving storage quality and pathogens resistance. It has been reportedthat 1-MCP treatment can reduce decay and extend storage life of various fruits, such as bananas, peaches, tomato, apples and broccolis. Chitosan, a versatile biopolymer derived from deacetylation of chitin hasbeen widely used in fresh keeping due to its good biodegradability, antibacterial activity and capacity toform film. It reduces moisture loss and slows respiration by reducing oxygen uptake. Chitosan coating hasbeen successfully applied to prolong storage life and control decay of many fruits, such as longan, litchi,strawberry and Indian jujube. Shengzhou Nane (Prunus salicina Lindl. var. taoxingli) is well known for itshigh nutritional value and pleasant flavor. Its fruit usually ripe in summer, when high temperatures accel⁃erate the processes of water loss, softening, microbial attack and decay during storage. As a result, thefresh fruit has a very short shelf life, deteriorating and losing marketability within a few days under ambi⁃ent temperatures. Therefore delaying postharvest fruit rotting process is the key to maintaining the high nu⁃tritional value of the fruit. The objectives of this study are to investigate and evaluate the effects of 1-MCP,chitosan coating and their combination on Shengzhou Nane fruit quality during storage.【Methods】Sheng⁃zhou Nane fruit (about 80% mature stage) were harvested from an orchard in Shenzhou city of Zhejiangprovince and immediately transferred to laboratory on the same day. Fruit with uniform size were selectedand treated with different concentrations of 1-MCP for 6 h, or with chitosan coating, or with 6.0 μL·L^-1 1- MCP combined with 1.0% chitosan coating, and the remaining fruit were treated with ddH2O andserved as the control. Fruit in each treatment were wrapped in a 0.2 mm polyethylene bag after air-driedand then stored at room temperature (26±1) ℃ with 90% relative humidity (RH). Quality parameters andcell structure integrity were analyzed during storage.【Results】Compared with the control, the separatetreatments with different concentrations of 1-MCP or chitosan had different effects on decay rate of fruitduring storage. For example, in the treatments with 6.0 μL·L^-1 1-MCP for 6 h and with 1.0% chitosan, thedecay rates of fruit were 19.12% and 23.92%, respectively, while that in the control was 62.82% after 8days of storage at ambient temperature. The results showed that both 1-MCP and chitosan coating treat⁃ments could significantly reduce the decay rate of Shengzhou Nane fruit after harvest. Moreover, comparedwith those treated with 1-MCP or chitosan coating alone, the fruit in the combined treatment of 6.0 μL·L^-1 1-MCP and 1.0% chitosan coating had significantly higher activities of antioxidant enzymes, such as su⁃peroxide dismutase (SOD) and catalase (CAT) and thus a lowest fruit decay rate. Increased activities ofSOD and CAT prevented overproduction of reactive oxygen species that cause degradation of membranelipids of cells resulting in structure collapse and malondialdehyde (MDA) accumulation. As a result, lowercontents of H2O2 and MDA and reduced oxidation injuries in the treated fruit were observed. Correspond⁃ingly, lowered weight loss and, increased fruit firmness and integrity of membrane and cell wall wereachieved. At the same time, the contents of vitamin C, total soluble solids and titratable acids in fruit under the combined treatment of 1-MCP and chitosan coating maintained significantly higher than under theother treatments and the fruit had the lowest decay rate and an extended shelf-storage life.【Conclusion】Our results showed that, under ambient temperature conditions, Shengzhou Nane fruit treated with 6.0μL·L^-1 1-MCP for 6 h combined with 1.0% chitosan coating had the lowest decay rate. It was suggestedthat 1-MCP and chitosan coating are effective in increasing the activities of anti-oxidation enzyme, reducing cell membrane peroxidation and MDA accumulation, inhibiting water loss and decay, maintaining fruitfirmness and membrane integrity and delaying fruit ripening process. As a result, an improved fruit stor⁃ability and thus prolonged storage life from 6 days to 12 days was achieved.