| Peach is one of the widely planted temperate-zone tree fruit in the world. Consumers like peach fruit extraordinary because of its special flavor. The storage and transport time of peach fruit in ambient temperature is limited because of the easy soft and decay. Low temperature can prolong the storage time,but peach fruit appears the severe symptoms of chilling injury easily,and the fruit lose the characteristical flavor, and even lose the edibale and commercial value. At present, Consumers and Scientist pay more attention to the postharvest flavor characteristics of peach fruit during low temperature storage.The experiment studied the influence of exogenous ethylene of different concentrations(0μl/L,5～10μl/L,10～20μl/L, 20～50μl/L, 50～80μl/L, 90～120μl/L) on the major flavor compounds and activities of relative enzyme of'Okubao'(Prunus persica L.)and'Bayuecui'(Prunus persica L.)peach fruit during CA(0-1℃,10%CO2+10%O2) storage and then 3 days shelf-life at 20℃, with the advancing technique of HS-SPME,further studied the influence of exogenous ethylene on the relative physiological indices of peach fruit and the interaction between exogenous ethylene and endogenous ethylene were also concluded.The results were as following.1.Exogenous ethylene treatments of different concentrations had different effect on the quality and relative physiological indices of peach fruit during CA storage and the shelf-life.Exogenous ethylene treatments with a lower concentration(5～10μl/L,10～20μl/L) had no obviously effect on some physiological characteristic and content of flavor compounds of peach fruit; Exogenous ethylene treatment with a higher concentration(90～120μl/L) aggravated the browning of peach fruit at the late period of storage, and the influence of exogenous ethylene to browning of peach fruit varied from storage to shelf-life, the influence to peach fruit of storage was mesocarp, while to peach fruit of shelf-life was mesocarp and endocarp; The treatment of exogenous ethylene with 50～80μl/L concentration could make peach fruit softening normally during CA storage and shelf-life at the late period of storage, however,the firmness of peach fruit which were stored in controlled atmosphere without exogenous ethylene and in low temperature appeared harden,and lost the ability of normal softening even at 20℃at the late period of storage, and the treatment of 50～80μl/L exogenous ethylene did not make the browning more serious.2.Exogenous ethylene treatments had some effect on the sugar and acid of peach fruit.Exogenous ethylene increased the total sugar content of peach fruit in the late period of storage, but did not affect the total sugar content obviously at 20℃for 3 days.The treatments of exogenous ethylene accelerated the decreasing of titratable acids content in the middle stage of storage, while slowed down the rapid decreasing of titratable acids content during the shelf-life.3.Exogenous ethylene treatments regulated the biosynthetic process of major volatile flavor compounds(Hexanal, Trans-2-hexanal, Benzaldehyde, Linalool,γ-decalactone), but the effect varied with different compounds. Exogenous ethylene treatments slowed the loss of Hexanal and Trans-2-hexanal , the two compounds had common biosynthetic pathway which depended on ethylene. Exogenous ethylene treatments also had some effect on the content of Benzaldehyde, Linalool,γ-decalactone, but the characteristic were not clear, therefore, it was conferred the biosynthetic pathway of the three compounds depended on ethylene and other factors.4.The effects of exogenous ethylene on flavor compounds and physiological characteristic of peach fruit were due to increasing of endogenous ethylene release rate which was stimulated by exogenous ethylene and increasing the activity of lipoxygenase. The ACC synthase had important effect on the biosynthetic pathway of endogenous ethylene, it influenced the biosynthetic process of ethylene. Exogenous ethylene increased the activity of ACC synthase, and then raised the endogenous ethylene release rate.The ACC oxidase also had some effect on the biosynthetic pathway of endogenous ethylene, but the influence of exogenous ethylene to ACC oxidase was not obvious.5. The enzyme related to synthesis of volatile flavor compounds were LOX, HPL,ADH and AAT in the pathway of LOX, they catalyzed the produce of flavor compounds of aldehydes, alcohols and esters respectively. Exogenous ethylene treatments influenced the activity of these enzyme. the change of these enzyme had to do with aldehydes, alcohols,and esters.It indicated that enzyme influenced the biosynthetic pathway of flavor compounds. In some extent, exogenous ethylene influenced the activities of related enzyme, and then regulated the content of volatile flavor compounds.The flavor of peach fruit stored in low temperature became tasteless or off-flavor because the related enzyme became inantivation.According to the above research results, exogenous ethylene played an important role in the process of physiological-biochemical of peach fruit stored in controlled atmosphere, and then influenced the quality of peach fruit, the influence of exogenous ethylene on the quality of peach fruit stored in conlled atmosphere manifested in the middle and late period of storage. Considering the comprehensive effects of different ethylene concentrations on the main feature of peach fruit, we concluded that the treatment with 50～80μl/L exogenous ethylene had the better effection.
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