Study On The Relationship Between Chilling Injury And Energy Metabolism In Postharvest Papaya Fruit

Papaya(Carica papaya L.)belongs to the tropical and subtropical fruits,postharvest papaya at normal temperature soon grows soft,senescence and finally rotten and deteriorated.Cryopreservation is a major method to maintain fruits' quality and prolong their storage life.But papaya is a kind of tropical fruits,so improper low storage temperature may trigger chilling injury to it.In order to explore the mechanism of chilling injury of papaya fruit,as well as the relationship between chilling injury and energy metabolism.Therefore,for this paper,the main varieties papaya named Zhong Bai in Hainan was used as the test materials,this thesis research focus on different levels of chilling injury at different storage temperature(respectively at 1 ?.6?.11?and 16?)and energy metabolism indexes as well as the effect of betaine on energy metabolism and chilling injury in papaya?The results are shown as follows:1.Through the storage of papaya at 1?,6?,1 1?and 16?,it indicated that the“Zhong Bai”papaya fruit which was storaged at 16? stayed away from chilling injury.From 11?to 6?,with the decrease of the temperature,the degree of chilling injury for fruit was aggravated.Compared with the fruit at 11?and 6?,the chilling injury of fruit at 1? was lighter,but the normal practice of the fruit still not happened at the end of storage.For the papayas at 6 ?,the activity of SOD.POD.CAT decreased most fastly,the production rate of O2 and the content of H2O2 were highest,the cell membrane permeability is the largest and Chilling injury is the most serious.But for the fruit at 1?,the special temperature could significant delay the appearance of active peak belonged to SOD?POD?CAT and relieve the subsequently decrease of the activity,which furtherly maintained the better anti-oxidant activity,the integrity of cell membrane and relieve the appearance of the chilling injure at the storage.2.The situations of energy metabolism of papaya fruit were changed with the different storage temperatures.For the papayas at 6 ?,the centent of ATP?ADP and the energy charge was the lowest,cell energy loss is most serious,and chilling injury is the most serious.The fruit at 11? was better,while the fruit at 1? kept higher energy level and the chilling injury was weaker.The chilling injury not happened at 16 ? and the fruit always maintained a mitochondrial respiratory metabolism enzyme activity and higher energy level,pyruvic acid content in fruit tissue was lowest.In the process of cold storage,the activities of SDH?CCO?H+-ATPase ? Ca2+-ATPase were lower,and the prevention of the energy metabolism processes resulted in the shortage of the cell energy.At 6 ?,the activity of mitochondrial respiratory metabolism enzyme dropped fastest.At the end of the low temperature storage,owing to the limit of the Krebs cycle,pyruvic acid content in fruit rised sharply and pyruvic acid content rised fastest at 6 ?.The results showed that the chilling injury may be related to the shortage of energy supply.3.The process with betaine could effectively reduce the chilling injury of papaya fruit during low temperature storage and significantly reduces the decay at the end of storage.During low temperature storage,the betaine could keep higher content of TSS and delay the decrease of the hardness and titratable acid.Furtherly,the betaine significantly improved the activity of SOD?POD?CAT and avoided the abnormal rise of the content of H2O2 and the productive rate of O2.-,reduced the the content of MDA and cell membrane permeability,maintained the integrity of cell membrane.4.The betaine could obviously improve the activity of SDH and H+-ATPase,relieve the rise of the content of Pyruvic acid,inhibit the content of ATP and ADP and the decrease of energy level.This showed that betaine treatment regulated the activity of enzyme related to cell energy metabolism,protected mitochondrial function,reduced the energy loss of fruit under low temperature stress,thereby alleviating chilling injury.