Effects Of 1-MCP Combined With UV-C Treatment On Postharvest Physiology And Aroma Compounds Of Xiaobai Apricot

‘Xiaobai’apricot is one of the characteristic agricultural products in Xinjiang,which is favored by consumers because of its sweet,delicious and nutritious characteristics.However,its commercial value is severely restricted due to its vigorous post-harvest life activities and difficult long-term storage.Therefore,it is in urgent need of economical and efficient storage and preservation methods to improve its edible and commercial properties 1-methylcyclopropene（1-MCP）could inhibit postharvest ethylene effect and delay senescence of fruits and vegetables.In this study,1-MCP fumigation and UV-C irradiation were combined to treat Xiaobai apricot,and the storage quality of Xiaobai apricot was analyzed to explore the feasibility and advantages of combined treatment,and provide theoretical basis and technical support for the application of 1-MCP and UV-C combined treatment in the storage and preservation of Xiaobai apricot.The main research results are as follows（1）Effects of 1-MCP combined with UV-C on physiological quality of Xiaobai apricotThe combined treatment of 1-MCP and UV-C can effectively reduce Xiaobai apricot fruit quality loss,maintain high fruit hardness,delay the increase of fruit soluble solid content in the early stage of storage,and maintain high soluble solid content in the later stage of storage,inhibit the decrease of fruit titratable acid.At the end of storage,its firmness,soluble solid content and titratable acid were 1.49,1.19 and 1.34times that of the control group,respectively.In addition,ethylene release and respiratory intensity were inhibited in the combined treatment compared with UV-C alone.Therefore,the combined treatment of1-MCP and UV-C can effectively delay fruit ripening and senescence,reduce fruit quality deterioration,and improve fruit quality after harvest.（2）Effects of 1-MCP combined with UV-C on antioxidant capacity of Xiaobai apricotThe 1-MCP treatment can effectively inhibit the accumulation of MDA and H₂O₂,decrease the production rate of O₂.^-,and delay the decrease of ASA content and antioxidant enzyme activities such as POD,CAT,APX and SOD.UV-C treatment can effectively promote the accumulation of secondary metabolites such as total phenols and flavonoids,delay the decrease of ascorbic acid content,and significantly increase the activities of antioxidant related enzymes such as POD,CAT,APX,SOD,and improve the DPPH clearance rate of fruits.However,the combined treatment of 1-MCP and UV-C combined the advantages of the two treatments,which could effectively promote the accumulation of antioxidant substances and the activity of antioxidant enzymes and enhance the antioxidant activity of the fruit,and the effect was better than that of UV-C or 1-MCP alone.（3）Effects of combined treatment of 1-MCP and UV-C on aroma metabolism of Xiaobai apricot during storageA total of 26 aroma compounds were detected by GC-MS,including aldehydes,terpenoids,alcohols and ketones.The characteristic aroma compounds of Xiaobai apricot included 2-hexenal,benzaldehyde,decalactone,linalol,terpinol,2-heptanol,β-ionone and other.The 1-MCP treatment could significantly inhibit the production of esters and alcohols and increase the contents of terpenes,while UV-C treatment could effectively promote the accumulation of esters and alcohols and the transformation of aldehydes,and increase the contents of ketones and terpenes.However,the combined treatment of 1-MCP and UV-C can effectively increase the contents of esters,alcohols,terpenes and ketones,and reduce the contents of aldehydes,and maintain a high content of esters terpenes in the later storage period,alleviating the inhibition effect of 1-MCP alone on aroma formation of apricot.The analysis of the changes of fatty acid content,enzyme activity and related gene expression showed that the combined treatment of 1-MCP and UV-C can effectively improve the activity of FAD and LOX enzymes and the expression of related genes,promote the desaturation process of fatty acids,improve the content of unsaturated fatty acids such as linolenic acid and linoleic acid,and provide precursors for the production of aroma substances in fatty acid metabolism pathway.In addition,the combined treatment can also improve the activities of AAT,HPL and ADH enzymes and the expression of related genes,and promote the accumulation of esters and alcohols during storage.Therefore,the combined treatment of1-MCP and UV-C can effectively improve the aroma quality of Xiaobai apricot fruit,and keep good flavor in the later storage period.