Mechanism Study On Hight Carbon Dioxide Induced Core Browning Of Postharvest Fruit Korla Fragrant Pear

Korla fragrant pear is one of the most famous specialty fruit in xinjiang.The fruit are popular withconsumers because of its good quality. Postharvest storage capacity of Korla fragrant pear fruit was above600,000tons, which played an important role to solve postharvest sales, but in the late storage,pear easilyprone to core browning, which seriously affected the quality of Pear and brought about huge economiclosses, which had become a key technical problem to effect postharvest storage of pear. This paper used thepear as test material to study the effect of core browning of pear with CO2concentration during storage, todiscuss mechanism of core browning and provide a theoretical basis to prevent postharvest core browning.The contents of research are as follows:1.Fragrant pear fruits were used as test material to study the effect of different CO2concentrations oncore browning and quality during storage. The results show that, treatments with1.5%~2%CO2and2%~2.5%CO2occured core browning phenomenon at the84d storage, pathogenesis rate of core browningwere respectively up to22.22%,27.00%at the140d storage, the other treatments not to exist corebrowning phenomenon occured during the whole storage. CO2concentrations less than1.5%~2%canrestrain respiration rate and aging of pear, delay the decline of hardness, Vc content, soluble solids,chlorophyll content and chroma corner of pear fruit during storage. The suitable atmosphere storagecondition of pear was CO2concentration below1.5%.2.Fragrant pear fruit were treated with CO2at2%~2.5%to study the effect of metabolism of high CO2concentrations on reactive oxygen and membrane lipid peroxidation. The results show that,the activity ofPOD, CAT, SOD, APX of core and pulp were significantly reduced by high concentrations of CO2, whichleaded to free radical scavenging capacity decline in core and pulp of pear fruit, caused H2O2, O2-.accumulation,meanwhile raised the LOX activity in core and pulp of pear fruit, leaded to the effect ofmembrane lipid peroxidation aggravation, MDA content elevation, the relative conductivity and membranepermeability enlargement, resulting core browning of pear occurred. High concentrations of CO2treatmentalso caused PAL activity elevation in core and pulp of pear fruit, promoted phenolic compounds synthesis, and provided substrate for the enzymatic browning.3.Fragrant pear fruit were treated with CO2at2%~2.5%to study the effect of high CO2concentrationson phenols and polyphenol oxidase activity. The results show that,core and pulp of pear contained arbutin,gallic acid, vanillic acid, caffeic acid, catechol and chlorogenic acid. Phenolics content in core of pear fruitwas significantly higher than in pulp,chlorogenic acid content is the highest in core and pulp,pH in core ofpear fruit was significantly lower than in pulp. The optimal substrates of PPO in core and pulp werechlorogenic acid,the optimum pH were respectively4.0,3.5.2%~2.5%CO2treatment promoted chlorogenicacid and total phenol decomposition in core and pulp of pear fruit,accelerated pH decline in core of pearfruit, meanwhile delayed PPO activity falling in core and pulp of pear fruit..