Influence Of UV-C Treatment On Mechanism Of Mushrooms (Agaricus Bisporus) Browning During Storage

Agaricus bisporus，as a kind of important exported mushrooms cultivated in China，owing to its delicious flavor，full of nutrients，is well received by consumers. However，at room temperature post-harvest loss of lots of water happens within48h，and theoccurrence of significant browning seriously affect their commercial value.Therefore，postharvest browning of mushrooms becomes an important issues.As a green and safe，economical and efficient non-thermal treatment technology， Ultraviolet-C （UV-C）irradiation treatment can inhibit the growth of microorganism，but also enhance postharvestdisease resistance，inducing fresh produce to produce functional ingredients，delayingripening and senescence.Study reported that UV-C technology can delay browning，but itsregulatory mechanism is not clear. In our study，intems of biochemistry，enzyme，we aimat researching the effect of UV-C treatment on the mechanism of mushrooms browningduring storage，with the purpose of providing a theoretical basis and technical reference forthe regulation of mushrooms browning during storage.1．Mushrooms were irradiated by UV-C with a dose of1kJ/m2， stored at4℃.Periodically determining caps browning related enzyme activity （PPO，POD，PAL），conten of related browning substrate （Tyr， GHB， GDHB）， reactive oxygenmetabolism-related indicators （O2-production rate，SOD activity，MDA content，embrane leakage rate），pathogenesis-related activity（CHT，GLU），color，texture duringstorage. The results showed that UV-C dose of1kJ/m2can inhibit the increase of capsPPO activity and the decrease of antioxidant activity （such as MDA content，etc.），as wellas membrane lipid cells peroxidation，maintaining the integrity of cell membranes，delaying the decline of color and hardness of caps，which will help maintain its quality，thus extending the storage life.2．Mushrooms were irradiated by UV-C with a dose of1kJ/m2，stored at4℃.Periodically determining caps，stipes and gills activity of PPO and POD，content ofMDA and total phenolics during storage. The results showed that：（1） PPO activity ofcap increased during storage and UV-C was lower than CK；while PPO activity of stipesand gills was decreased and UV-C was higher than CK（.2）POD activity of caps，stipes andgills showed a great difference.POD activity of caps decreased and UV-C was higher thanCK during21d strorage；POD activity of stipes rise during0-7d，on the7th day CK wassignificantly higher than UV-C，7-21d both CK and UV-C treatment decreased；PODactivity of gills rise and UV-C was higher than CK.（3）MDA content of stipes decreasedduring storage and UV-C was higher than CK latterly；MDA content of caps and gills is rising.As to caps，UV-C is lower than CK during storage.As to gills，UV-C was higher thanCK.（4）The three parts of the total phenolic content showed a downward trend duringstorage；As to caps，UV-C was higher than CK，opposite to stipes.3. Mushrooms were irradiated by UV-C with a dose of1kJ/m2，stored at4℃. PPOisoenzmes were extracted from the mushroom cap，stipe，gill，detected by Native-PAGE，analyzed by Bio-Rad gel imaging system.The results indicate that there are a total of fourmushroom PPO isozymes，with respective molecular weights of90kDa，70kDa，67kDa，45kDa. On the1st day during storage，among stipes，gills and caps，there are four，three（without45kDa band）and three bands（without45kDa band），respectively；on the7thday，there are respectively three（without67kDa band），one（only90kDa），three（without67kDa band）；on the14th day，there are only two bands（90kDa and45Kda）. Themolecular weight of90kDa PPO isozyme maintain a higher activity among the threeparts of mushrooms than any other PPO isozymes. Compared to other PPO isozymes，90kDa of PPO isoenzyme is the main reason causing browning during storage.45kDa ofPPO isoenzyme began to play a role in browning from the7th day. Activity of67kDa and70kDa PPO isoenzymes disappeared gradually during strorage.