Effects Of NO On The Quality And The Metabolism Of Phenylpropane And Anthocyanin In Raspberries During Storage

Red raspberries are rich in nutrition and sweet and sour,can be eaten raw or further processed,and gradually enter the fruit market.However,the raspberry is thin and soft,and it is easy to soften and rot after harvesting,which shortens the shelf life and restricts its economic value.Therefore,finding a simple and safe method for postharvest raspberry preservation has become the key to opening the raspberry market.Nitric oxide?NO?is an important signal molecule in plants and has a good effect on the freshness of vegetables after harvesting.In this experiment,‘Australian Red'raspberries were used as materials.They were immersed in different concentrations of nitric oxide solution(0,0.25,0.5,0.75?mol·L^-1)and nitric oxide(0,0.25,0.5,0.75?L·L^-1)fumigation treatment of red raspberries to explore the effects of exogenous NO treatment on the quality and antioxidant system of postharvest raspberry fruits,phenylpropane metabolic pathways,and anthocyanin metabolic pathways.The optimal NO-treated concentration of raspberries provides experimental evidence for NO in the preservation of raspberries.?1?Compared with the control,0.5?mol·L^-1 NO immersion and 0.5?L·L^-1 NO fumigation delayed the weight loss rate of the fruit,reduced the respiration of the fruit during storage,and improved the soluble solid contents?SSC?in the raspberry,maintained the good quality of raspberries after harvest.0.5?mol·L^-1 NO immersion and 0.5?L·L^-1 NO fumigation increased the activities of superoxide dismutase?SOD?,peroxidase?POD?,and catalase?CAT?in raspberry fruits,enhanced the antioxidant capacity by inhibiting the activities of polyphenol oxidase?PPO?and lipoxygenase?LOX?,maintained the appearance quality of raspberry fruit and the integrity of cell membranes,reduced malondialdehyde?MDA?content.0.5?mol·L^-1 NO immersion and 0.5?L·L^-1 NO fumigation increased the activities of monodehydroascorbate reductase?MDHAR?,dehydroascorbate reductase?DHAR?,glutathione reductase?GR?,ascorbate peroxidase?APX?activity,accelerated the elimination of excess hydrogen peroxide,increased the contents of ascorbic acid?AsA?and glutathione?GSH?,and reduced the accumulation rate of dehydroascorbic acid?DHA?and oxidized glutathione?GSSG?,increased the ratio of AsA/DHA and GSH/GSSG,so that postharvest raspberry cells were in a highly reduced state and maintained normal physiological activities.0.5?mol·L^-1 NO immersion and 0.5?L·L^-1 NO fumigation improved the scavenging ratio of hydroxyl radical?·OH?,superoxide anion radical?·O₂^-?and hydrogen peroxide?H₂O₂?of postharvest raspberry fruits,enhanced the ability to scavenge 1,1-diphenyl-2-picrylhydrazy?DPPH?free radicals and promoted the antioxidant capacity of postharvest raspberries.?2?0.5?mol·L^-1 NO soaking and 0.5?L·L^-1 NO fumigation improved the activities of shikimate dehydrogenase?SKDH?,phenylalanine ammonia lyase?PAL?,cinnamate 4-hydroxylase?C4H?and 4-coumarate coenzyme A ligase?4CL?,accelerated the accumulation rates of total flavonoids,total phenols and lignin in the phenylpropane metabolites,increased the ability of raspberries to remove reactive oxygen species,and enhanced the disease resistance.?3?0.5?mol·L^-1 NO immersion and 0.5?L·L^-1 NO fumigation promoted the activities of anthocyanin synthase?ANS?,chalcone isomerase?CHI?,dihydroflavonol reductase?DFR?and flavonoid glucosyltransferase?UFGT?,and increased total anthocyanin content in post-harvest raspberry entities.The results showed that,compared with other treatments,0.5?mol·L^-1 NO soaking and 0.5?L·L^-1 NO fumigation had the best effects on post-harvest raspberry quality,phenylpropane metabolism,and anthocyanin metabolism pathways,which provided the basis for the postharvest raspberry preservation.