Study On Quality And Physiological Metabolism Of Huanghua Pear During Ice-Temperature Storage

Huanghua pear(Pyrupyrifolia Nakai,cv.Huanghua)is an excellent variety of Chinese pear bred by modern scientists in our country.It is sweet,crispy taste and nutritious,resulting in good edible value and economic value and has a long storage period in low temperature.In order to preliminaryly explore the expression of its cold resistance resulting from life metabolism of the pear at low temperature,this study investigated the effect of ice temperature storage and different outgoing methods on the quality of Huanghua pear,and determined the sucrose metabolism and active oxygen metabolism during the storage.Also,the effect of salicylic acid pretreatment on active oxygen metabolism was measured.The paper preliminary explore life metabolism of Huanghua pear in low temperature environment for the expression of its cold resistance.1.The storage quality and cold resistance of Huanghua pear during ice-temperature storage:this paper compared the changes of storage quality at two different storage temperature(-1? and 5?).And the changes in the content of free proline and soluble protein were also measured.The results showed that the decline of the hardness,soluble solids content and titratable acid content were slowed down,and also the increase of respiratory intensity(p<0.01)and weight loss rate were inhibited(p<0.05)during the ice-temperature storage.Also,the decrease of titratable acid content after 60 days was significantly inhibited(p<0.01).Results suggested that the cold resistance was not relevant with the heat resulting from the increase of respiration intensity.Its cold resistance gradually began to exert with the ripening of the fruit and the increase of proline content.2.the effect of different outgoing way on the quality of Huanghua pear after ice-temperature storage:The quality changes of pears between direct outage method and gradient heating out(-1??5??15?)method were compared.Results showed that using gradient heating out method,the change of the respiration intensity and weight loss rate of Huanghua pear during shelf life were relatively stable,and hardness and soluble solid content were slowed down.The decrease of titratable acid content(p<0.05)and soluble content(p<0.01)was significantly inhibited.Sugar-acid ratio of the pears using gradient heating out method was higher than those using the direct outgoing one during the shelf life.The gradient of warming pear had higher commodity value.3.The changes of sucrose metabolism and related enzyme activities during ice storage.The pears at two different storage temperature(-1 ?and 5 ?)were compared.The results showed that the sucrose metabolism of Huanghua pear during the storage favored the direction of decomposition.The content of total sugar,fructose and glucose increased at first and then decreased during the storage.The decrease of glucose content after 60 days of ice-temperature storage was significantly inhibited(p<0.05).The content of sorbitol and sucrose decreased continuously and the ice-temperature storage had significantly inhibitory effect on the decreasing trend(p<0.05).In addition to the fructose content,the fructose content of the pears from-1 ? group was higher than that of the 5 ? group.And the activity of sucrose phosphate synthase of the pears from-1 ? group was significantly higher than that of the 5 ?group.After 90d,the activity of AI and NI of the pears from the 5?group kept constant with slight increasing.The activity of those enzymes of the pears stored at-1? decreased to a relatively low level,and the AI activity of the pears significantly decreased(p<0.05).Therefore,the sucrose metabolism of Huanghua pear gradually weakened which maintained the carbohydrates of the pears stable.4.The effect of ice-temperature on the active oxygen metabolism in Huanghua pear during the storage.The pears at two different storage temperature(-1 ? and 5 ?)were compared.The results showed that ice-temperature storage could inhibit the increase of H2O2 content and O2-generation rate in Huanghua pear fruit during the storage,and maintain APX,POD and SOD of the pear fruit in high activity during the storage(p<0.05).But the effect of ice-temperature on the CAT activity was not significant.And the content of salicylic acid remained at a relatively high level during the ice-temperature storage.5.The effect of salicylic acid pretreatment on active oxygen metabolism of Huanghua pear during the ice-temperature storage.Huanghua pears were soaked in salicylic acid of concentration of Og/L,0.1g/L and 0.2g/L for 0.5 hour.Then the active oxygen metabolism of the pears at two different storage temperature(-1 ?and 5?)were compared.The results showed that the activity of APX(p<0.05),SOD(p<0.05)and POD in the salicylic acid treatment group increased,while the accumulation of H2O2(p<0.05),the production rate of O2-(P<0.05)and the activity of CAT were inhibited.The changes in the activity of enzymes,including APX,CAT,POD and SOD of the pears between the treated groups and the control group was larger under-1 ? condition compared to 5 ? condition.Therefore the metabolism of active oxygen of Huanghua pear which stored at-1 ? were more sensitive to the change in salicylic acid content.