Study On The Storability And The Preservation Efect Of Chemicals On Green Walnut Fruit

To investigate the influence of varieties and harvest stage on storability of fresh walnutgreen walnut （Juglans regia L.） fruits from three harvest stages i.e. I （August23）, II （August29） and III （September4）, of Xifu No.2and three verieties of Liaoning No.2, Luguang,XifuNo.2were stored at0¹℃. Biological changes and preservation result were analyzed duringthe storage. Fruit cv.Xifu No.2also accepted postharvest treatment of either additional orcombined ClO₂,1-MCP, then refrigeration stored to test the chemical preservation effectthrough determining series of physiological-biochemical indices and statstating decay indexetc.The objective of this study is to provide theoretical and practical basis for fresh walnutstorage.All the results show as following:（1） Xifu No.2fruit from harvest stage I, II and III were in the period of before, during, afterfirst respiration climacteric, respectively. they continued the mature progress which happenedon the mather tree to present, undergo, complete the first climacteric, in turns. After24daysfruits from the three harvest stage all showed thesecond respiration peak, which of the fruitfrom harvest I were lower and6d later than that from harvest II, III. Ethylene release peak offruits from three harvest stages appeared on day42,36,30, respectively,being earlier with thedelaying harvest stage. Decay index （DI） of fruits from three harvest stagesdifferedsignificantly,which was low in the first stage, increased since24d, accelerated33d after.DI offruit from harvest stage I rose the fastest, followed by II, the slowest rise occurred on harveststage III fruit. In the end of storage DIfor fruit from harvest stage I,II and IIIwas31.47%,17.80%and12.67%,respectively, the first value is significantly higher than that of the latertwo. Kernel rate of fruits from three harvest stageswere:38.42%,40.41%and41.51%,thelater the harvest stage is, the higher the rate is. ABA, IAA, GA, showed a late rise,corresponding to ethylene release peak. Zeatin （Zr） presented a peak in the first stage, thenrose the final.（2） Date when two postharvest respiration peak appeared for fruits from3varieties werenot the same. They for the twice respiration climacteric of Liaoning No.2fruit were12d,36d,respectively, being6^-12d later than the other two varieties and indicating subtledifferences between mature stages of three varieties.Ethylene release amountpeaked on30d for Liaoning No.2fruit, being6d earlier than Xifu No.2and Luguang and4-folder higher thanthem.Within30dDIs of fruit from three harvest stages were not significantly different,whichof Liaoning No.2increased significantly less,thereafter,after42d the DI increase of Luguangbecameless than that of Xifu No.2. In the end of48-daystorage DI of Liaoning No.2, LuGuang, Xifu No.2were14.00%,17.8%,21.07%, respectively.（3）Fruit cv.Xifu No.2accepted postharvest treatment of either additional or combinedClO₂,1-MCP showed different preservation result.The walnut fruit was treated by water（control）,80mg L^-1ClO₂（ClO₂）,0.5μL L^-11-MCP （1-MCP）, or combination treatment of80mg L^-1ClO₂with either0.1μL L^-11-MCP （0.11-MCP+ClO₂） or0.5μL L^-11-MCP （0.51-MCP+ClO₂）. All treatments decreased postharvest respiration intensity in different degreesand inhibited ethylene production peak. ClO₂increased the total phenol and flavonoid contentof the green fruit compared with other treatments and the control （p<0.05）, but not did thetotal antioxidant activity for this treatment. After42-day storage, ClO₂remained higher freshweight and lower decay index than control, while1-MCP increased the fruit decay index.Final acid values of kernel from ClO₂, control and0.11-MCP+ClO₂were not different fromtheir initial values, which from0.51-MCP increased. Final peroxide value for kernel fromClO₂showed no change during storage but increased at least1.0-fold for other treatments.ClO₂preserved99.9%of initial free fatty acid, similar to that for the control （99.8%）, whereas0.51-MCP preserved only95.7%. ClO₂is of potential in decay retardation and kernel traitsmaintenance of green walnut fruit, whereas the1-MCP has a negative effect for decay controlon walnut.In total, the walnut fruit harvest closer to the mature is storability. The harvest period IIIis better considering the cost of storage, nutritional value and extend the market supplycapacity. Varieties choose Liao2is better; after harvest treated with ClO₂, peeling stagelywhen the decay index was20-30%and continue to store or sale.