Effects Of Hot Water And 1-MCP Treatment On Preservation Of Fresh Broad Bean At Ambient Temperature

Broad bean is in season at the end of spring and early summer around the drainage areas of the Yangtze River.At present,fresh broad bean fruit mostly sells with pods in urban areas and supermarkets while broad bean pods are especially vulnerable to browning,yellowing even deterioration at ambient temperature,leading to its intolerance of transport and storage.Heat treatment as a physical preservation technology,which is low-priced and with no remain,could improve the quality of fruit at storage period.Treatment with1-methylcyclopropene（1-MCP）has the remarkable advantages of being highly efficient,safe and easy to operate,which is widely applied to delay the senescence of postharvest horticultural products.Therefore,it is vital to provide feasible and effective preservation technology for fresh broad bean.Therefore,physical method of hot water soaking and chemical method of 1-MCP fumigation treatment were applied to preserve the“Tongcan 6”fresh broad bean.Moreover,the influence of the hot water treatment and 1-MCP treatment on preservation effect and related metabolism were investigated in the hope of providing technical and theoretical support for the postharvest preservation of fresh broad bean fruits.The results were as follows:1.The effects of hot water treatment at 45℃for 10 min on browning,quality of fresh broad bean,chlorophyll degradation metabolism,ROS metabolism and phenylpropanoid metabolism were investigated.The results showed that hot water treatment could maintain the apparent color,Vc content and good seed rate,retard the increase of activities of PPO and POD,respiration rate and malondialdehyde（MDA）content as well as the oxidation of phenols.Meanwhile,the activities of chlorophyllase and Mg-dechelatase,related to chlorophyll degradation,which were inhibited by hot water treatment.In addition,not only the O2^-.production rate and H₂O₂ content was inhibited,but the activities of antioxidant enzymes（SOD,CAT,APX）and phenylpropane metabolism related enzymes（PAL,C4H,4CL）were enhanced by hot water treatment,which improves the scavenging ability of DPPH free radical and hydroxyl free radical.Aging symptoms such as browning and green degeneration were suppressed by hot water treatment with maintaining the homeostasis of ROS metabolism,promoting the phenylpropanoid metabolism and delaying chlorophyll degradation.2.The effects of 1μL·L^-1 1-MCP treatment on preservation effect,chlorophyll degradation,ROS metabolism and phenylpropanoid metabolism of broad bean fruit were studied.Research suggested that 1-MCP treatment not only had the evident effect on the suppression of PPO and POD activities and the consumption of phenolic substrates,but inhibited the increase of respiration rate and MDA content,which had an effective preservation effect on good seed rate,Vc and chlorophyll content.The results showed that1-MCP treatment inhibited the activities of chlorophyllase and Mg-dechelatase,thus inhibiting the degradation of chlorophyll.In addition,1-MCP treatment increased the activities of antioxidant enzymes such as SOD,APX and CAT in active oxygen metabolism,and stimulated the activities of key enzymes in phenylpropane metabolism,thereby enhancing the ability of free radical scavenging.Therefore,1-MCP treatment may improve the antioxidant capacity of pods by maintaining the balance of ROS metabolism and stimulating phenylpropane metabolic activity,so as to maintain the chlorophyll content in pods,slow down the yellowing of pods and delay the surface browning.