Studies On The Relationship Between Maturity And Chilling Tolerance Of Chinese Olive Fruit And Its Mechanism

Chinese olive[Canarium album(Lour.)Raeusch]is a kind of cold-sensitive fruit,which is quite easy to cause chilling injury and quality deterioration when stored under low temperature.’Tanxiang’ Chinese olive[Canarium album(Lour.)Raeusch cv Tanxiang]fruit was used as the experiment material,which was the chief Chinese olive cultivar in Fujian Province of China.Harvesting Chinese olive fruits with different maturities,we studied on the mechanism and the relationship between chilling resistance and physiological quality,active oxygen metabolism,metabolism of membrane lipids,energy metabolism and phenolic metabolism of Chinese olive fruits stored at(2±1)℃ and 90%relative humidity.The results were as follows:1.The effects of seven different maturities(Ⅰ,Ⅱ,Ⅲ,Ⅳ,Ⅴ,Ⅵ,Ⅶ)on the physiological quality and chilling injury of cold-stored Chinese olive fruits were studied.Compared with the Ⅰ,Ⅱ,Ⅲ,Ⅳ,Ⅵ,Ⅶ maturity,the V maturity could decrease the weight loss rate,increase healthy fruit percent,decrease the chilling index and browning index of pericarp,decrease the respiration and respiratory peak of fruits,decrease the drop of h value during the late storage stage,keep high contents of chlorophyll in pericarp,TSS,soluble sugar,TA and tannic in pulp.So the physiological quality and the chilling resistance of the V maturity fruits are the best.2.Based on the results above,the relationships between the chilling resistances of fruits with Ⅰ,Ⅲ,Ⅴ,Ⅶ maturities and the active oxygen metabolism,membrane lipid metabolism,energy metabolism and phenolic metabolism were studied.The results were as follows:(1)Compared with the Ⅰ,Ⅲ,Ⅶ maturity,the V maturity could keep high activities of the active oxygen scavenging enzymes such as SOD,CAT and APX,and keep high contents of endogenous antioxidants such as AsA and GSH in pulp and pericarp,decrease the accumulation of MDA and the production rate of O2-·Therefore,the V maturity delayed the appearance of chilling injuries by increasing the abilities of removing reactive oxygen species and decreasing the accumulation of them,decreasing the membrane lipid peroxidation,keepping the structure and function of cell membrane stable.(2)Compared with the Ⅰ,Ⅲ,Ⅶ maturity,the V maturity could decrease the activities of relative hydrolases such as PLD,LOX and lipase in pericarp and pulp,delay the decrease of unsaturated fatty acids(Oleic acid,Linoleic,and Linolenic),keep the membrane lipid unsaturation index(IUFA)and the unsaturations of fatty acids(U/S)high.So the V maturity could delay the chilling injuries of the cold-stored Chinese olive fruits by decreasing the activities of relative hydrolases and degradation of unsaturated fatty acids,make the cell membrane keep complete structure.(3)Compared with the Ⅰ,Ⅲ,Ⅶ maturity,the V maturity could inhibit the decrease of ATP and ADP contents in pulp and pericarp,inhibit the increase of AMP content,increasing the activities of Ca2+-ATPase、Mg2+-ATPase、H+-ATPase and NADK,keepping the NADP(H)content high.So the V maturity delay the chilling injuries of cold-stored Chinese olive fruits by providing energy of physiological metabolism and keeping the ion balance and permselective of the membrane,make the cell membrane keep complete structure..(4)Compared with the Ⅰ,Ⅲ,Ⅶ maturity,the V maturity could effectively decrease the activities of PPO,POD,and in pulp and pericarp of Chinese olive fruits,delay the decrease of PAL activity,total phenols and flavonoids contents.Therefore,the V maturity could delay the chilling injuries of cold-stored Chinese olive fruits by decreasing the activities of phenolic oxidase enzymes to inhibit phenolic oxidation.In summary,the V maturity is the suitable harvest maturity to decrease the chilling injuries when ’Tanxiang’ Chinese olive fruits stored at(2±1)℃ and 90%relative humidity.