Effects And Mechanisms Of 1-MCP And Ethephon On The Quality Of Fresh-cut Chinese Water Chestnuts

Chinese water chestnut（Eleocharis tuberosa,CWC）is an aquatic vegetable that is rich in nutrients and has high medicinal value.China is one of the world’s largest producers of CWCs.CWCs usually need to be peeled before eating,and recently fresh-cut CWCs have become a popular ready-to-eat product that meets the demands of consumers’busy urban lives.However,the fresh-cut process makes fresh-cut CWCs susceptible to nutrient loss,browning of the cut surface and microbial spoilage,which seriously affects the commercial value of fresh-cut CWCs.Therefore,the study of fresh-cut CWCs preservation technologies and mechanisms is an important issue at this stage.1-MCP has been used as a novel preservative to maintain the postharvest quality of many fruits and vegetables.It has also been found that exogenous ethylene can delay the deterioration of fruits and vegetables by increasing their antioxidant capacity.In addition,the combined application of 1-MCP and exogenous ethylene can alleviate the adverse effects of 1-MCP alone on the sensory quality of fruits and vegetables.Currently,there are few reports on the effects and mechanisms of 1-MCP alone or in combination with ethephon on the storage quality of fresh-cut CWCs.In this study,the effects and physiological mechanisms of ethephon and1-MCP on the quality of fresh-cut CWCs were investigated using sensory,physiological and biochemical analyses.q RT-PCR was used to explore the key genes involved in the regulation of browning of 1-MCP and ethephon to provide theoretical support for the storage and preservation of fresh-cut CWCs,and the results of the study were as follows:（1）Both 1-MCP and ethephon treatments delayed the quality deterioration of fresh-cut CWCs,and the optimal condition for 1-MCP soaking treatment was determined as 5 mg/L 1-MCP soaking treatment for 1 h;the optimal condition for ethephon soaking treatment was 3.4 g/L ethephon soaking treatment for 5 min.Ethephon was more effective than 1-MCP treatment in maintaining the appearance of fresh-cut CWCs.1-MCP and1-MCP preceding ethephon treatments were able to maintain weight and inhibit respiration,while ethephon whether followed 1-MCP or not were able to promote weight loss and stimulate respiration.（2）Ethephon-treatment reduced PAL activity to inhibit flavonoid accumulation,increased CAT and SOD activities and inhibited MDA level to maintain ROS balance and inhibit microbial growth.Compared to the ethephon preceding 1-MCP treatment,the1-MCP prior to ethephon treatment inhibited flavonoid levels and POD-catalyzed oxidation and increased CAT activity,delayed H₂O₂ production and microbial spoilage.（3）Ethephon treatment could significantly down-regulate the expression of Cw PAL,Cw CHS1-3,Cw CHI1/2 and Cw MYC2 in the phenylpropane pathway,which was down-regulated by 1-MCP alone or in combination with ethephon in the early stages of storage and induced to varying degrees in the middle and late stages of storage.The inhibition of Cw MYC2 and Cw CHI1 expression might be critical for 1-MCP and ethephon’s regulation of flavonoid accumulation in fresh-cut CWCs.Both 1-MCP and ethephon induced the expression of CwERF4B,which was significantly negatively correlated with browning,but the activation effect of 1-MCP was weaker than that of ethephon;both 1-MCP and ethephon inhibited the expression of CwERF5-like,but the inhibitory effect of ethephon was stronger than that of 1-MCP,and when ethephon was applied alone or in combination with 1-MCP,CwERF5-like showed a significant negative correlation with·OH production rate.The regulation of CwERF4B and CwERF5-like by1-MCP and ethephon might be vital in their role in delaying quality deterioration in fresh-cut CWCs.