Study On Quality Deterioration Of Postharvest Guanxi Mi-you

Changes of postharvest physiological qualities,texture proporties,lignin metabolism,active oxygen metabolism and energy metabolism were studied in Citrus guanxi mi-you fruit during storage at 25?and 5?.The relationships between them and granulation in juice sacs were investigated to clarify the reason and the mechanism of granulation in juice sacs of Guanxi honey pomelo fruits.The results were as follow:1.During storage period of Guanxi honey pomelo,TTS,titratable acidity of Guanxi honey pomelo juice sacs decreasaed,respiratory rate increased,all texture parameters increased with extending storage time,while weight loss didn't show an obvious regulation.Low temperature?5??can inhibit the increase of respiratory rate,decrease nutrients depletion,obtain low weight loss,delay all texture parameters of juice sacs addition.2.During storage period of Guanxi honey pomelo,granulation index of juice sacs.lignin content increased with extending storage time.The correlation coeffients indicated that granulation index had a positive correlation with lignin content and the acculation of lignin might rusult in juice sacs granulation.Low temperature?5??can decrease lignin biosynthesis by inhibiting relative enzyme activities of PAL,CAD,PPO.Therefore,low temperature?5??is good for decreasing the grannlation index of juice sacs.3.During storage period of Guanxi honey pomelo,the changes of enzyme activies POD,SOD,CAT were not synchronized,active oxygen metabolism were imbalaned.The menberance permeability,the content of MDA,the accumulation of H₂O₂ increased with textending storage time.Low temperature?5??can obtain high protective enzyme activies,decrease the menberane permeability,the content of MDA,the accumlation of H₂O₂.The metabolism imbalance of active oxygen may result in the granulation of juice sacs.4.During storage period of Guanxi honey pomelo,the content of ATP,ADP decreased with extanding storage time,while energy change leave and the content of AMP didn't slow an obvious regulation.The mechanism of granulation in juice sacs may be lack of energy.Low temperature?5??can obtain higher ATP and ADP content by accommodating the mitochondria CCO,SDH,H⁺-ATPase and Ca²⁺-ATPase activity.Therefore,juice sacs tissue maintain a higher enery level which is good for decreasing the granulation index of juice sacs of Guanxi honey pomelo.