Effect Of Cold Shock Treatment On Some Postharvested Physiological And Biochemical Changes Of Nectarines During Cold Storage

The effects of cold shock treatment (CST) on respiration rate ,ethylene production ,the variation of cellwall substance (cellulosepectin ), the activities of amylase correlated with softening and the qualities of"Qinguang 2"nectarine fruits were studied during cold storage .The mechanism of CST to delay ripening and senescence ,inhibit softening ,reduce the occurrence of chilling injury were also studied in the view of physiological and biochemical .The results were as follows :(1) CST delayed the ripening and softening of nectarine and the treatment of 0℃cold air for 3.5h was the best ,which kept the nectarines 60 days at 1±0.5℃cold storage .The decay rate was only 13.6% and 32% lower than that of control.(2) CST decreased the respiration and ethylene production of nectarines .The peak of respiration rate and ethylene evolution occurred 6 days later than CK .(3) CST inhibited the softening of nectarine and kept high firmness than those at room temperature .It because that CST restrained the hydrolysis of cellulose and pectin ,retained the amylase activities relating to fruits softening like PG,CX and LOX .(4) CST induced cold tolerance in nectarine fruits .Enzymatic analysis showed that SOD,CAT and POD activities of the treated nectarine fruits were higher than those of the control .MDA content and membrane permeability were lower than those of control .As the result ,CST enhanced the levels of free radical cleaning ,alleviated lipid peroxidation and maintained better cell membrane integrity ,and reduce the occurrence of chilling injury.The chilling injury of CST was 10% and 66.7% lower than that of control.(5) CST decreased the weight loss rate ,but there were no remarkable effect on the TSS and titratable acid of nectarines .So it kept the fruits'favor and qualities better .