Regulation On The Antioxidant System And The Umamit Of The Postharvest Agaricus Bisporus During The Senescence Process

Agaricus bisporus is the largest edible fungus for production and consumption in the world.It is rich in nutrients,and is called"plant meat".However,Agaricus bisporus is a climactic fungus,has strong metabolism,high moisture content,delicate tissue and no protective layer on the surface.Therefore,it is prone to suffer many problems such as water loss,browning,membrane break,rot,which can reduce the commodity value.At present,the preservation technology of Agaricus bisporus at ambient temperature is far less than the low temperature storage technology.The post-harvest Agaricus bisporus is attacked by free radicals that can seriously affect the content of umami ingredients.Therefore,studying the oxidation process and the regulation of umami can be helpful to further understand the aging process.In this experiment,both immersion[control,1.5%L-cysteine?L-Cys??w/v?,1mmol·L^-1 chitosan?CS?]and fumigation[control,30 mg·L^-1 1-methylcyclopropene?1-MCP?,0.1%sodium hyposulfite?SH??w/w?,30 mg·L^-1 1-methylcyclopropene+0.1%sodium hyposulfite?1-MCP+SH?]were used to treat Agaricus bisporus.The main findings were as follows:The treatments with CS,L-Cys,1-MCP,SH,1-MCP+SH had certain inhibitory effects on the browning and the opening of the mushroom during storage.The treatments with L-Cys and 1-MCP+SH significantly inhibited the opening,the browning,and the respiration of Agaricus bisporus fruiting bodies,and effectively eliminated the contents of reactive oxygen species?ROS?,superoxide radical?^·O₂^-?,hydroxyl free radical?·OH?,and hydrogen peroxide?H₂O₂?,increased the clearance rates of 1,1-diphenyl-2-trinitrophenylhydrazine?1,1-Diphenyl-2-picrylhydrazyl radical,?DPPH?,2,2'-azino-bis?3-ethylbenzothiazoline?-6-sulfonic acid,ABTS?,and ferric ion reducing antioxidant power?FRAP?.By increasing the activities of catalase?CAT?,superoxide dismutase?SOD?,ascorbate peroxidase?APX?,glutathione reductase?GR?,monohydroascorbate reductase?MDHAR?,and dehydroascorbate reductase?DHAR?,the oxidation resistance was enhanced.Simultaneously,the treatment inhibited the activities of polyphenol oxidase?PPO?,peroxidase?POD?,regulated the metabolism of the reduced ascorbic acid?AsA?and dehydroascorbic acid?DHA?to maintain the balance of the antioxidant system.The treatments regulated the contents of umami amino acids and nucleotides,maintained the contents of vitamin C,soluble protein,total phenol and reduce sugar,delayed the aging of fruiting bodies and improved the storage quality.L-Cys,1-MCP+SH could effectively inhibit the expression of the gene and the activity of PPO,thereby delayed the process of browning and prolonged the storage life of Agaricus bisporus.