Effects Of Different Pre-treatments On Postharvest Storage Of ’Ji Mei’ Sweet Cherry

The aim of this study was to investigate the effects of potassium cinnamate(PC)treatment at different temperatures on the room-and low-temperature storage of ‘Ji mei’ sweet cherry.Four treatments were set up for the experiments,the cherries were immersed into ice water at 0℃(CS),hot water at 45℃(HS),ice water combined with5 g/L PC solution(CS+PC),and hot water combined with 5 g/L PC solution(HS+PC)for 6 min,respectively.The cherries were immersed into distilled water at 25℃ as control(CK).The cherries were stored at room-temperature(25±0.5℃,RH 50%)and low-temperature(1±0.5℃,RH 90%).Indicators related to fruit quality and antioxidant properties were measured regularly,and the results were as follows:1.During the post-harvest storage at room-temperature,the increase of fruit respiration rate was inhibited by the CS,CS+PC,HS and HS+PC treatments in different degrees,which maintained the fruit firmness and the stability of total soluble solids(TSS)and titrable acid(TA)content,and delayed the decline of fruit brightness(L*)and color saturation(C*).Among theme,CS+PC treatment had the best effect.At the end of storage,the firmness of fruits in CS+PC treatment was 1.15 times higher than that of in CK,while the content of TSS,value of L* and C* were increased by15.43%,14.23% and 44.11%,respectively.In addition,the total antioxidant capacity(T-AOC)of fruits were increased by all the treatments,the activities of polyphenol oxidase(PPO)and peroxidase(POD),and the contents of secondary metabolites such as total phenols,flavonoids,anthocyanins and ascorbic acid(As A)in fruits were significantly increased,and the accumulation of malondialdehyde(MDA)in fruits were effectively inhibited,hence the degree of membrane lipid peroxidation was reduced,and with significantly reduce in fruit decay and weight loss.The peak value of PPO and POD activities of fruits in CS+PC treatment were 2.23 and 2.49 times of in CK,respectively,which were significantly higher than those of other treatments.At the end of storage,MDA content of fruits in CS+PC treatment was decreased by46.02%,the rotting rate and weight loss rate were decreased by 52.55% and 54.55%,respectively,which were significantly lower than those in other treatments.The overall effect of cold shock treatments was better than that of heat shock treatments at room-temperature storage.2.In the low-temperature storage,the storage quality of fruits was improved by all the treatments,the decline of firmness,sugar and acid content were delayed,and the activities of defense-related enzymes and the content of antioxidant secondary metabolites were increased,and with reduce in the weight loss rate and rotting rate of fruits.At the early stage of storage,the fruits treated by CS and CS+PC maintained a lower respiration rate and higher TSS,TA,total phenols and anthocyanins,and the activities of PPO,POD,superoxide dismutase(SOD)and cinnamic acid-4-hydroxylase(C4H)in fruits were induced.In the middle and late period of storage,the increase of fruit respiration rate in HS,HS+PC and CS+PC treatments were better inhibited,the fruits maintained higher firmness,TSS and TA content,and the activities of PPO,POD,SOD,phenylalanine ammonialase(PAL),C4 H and4-komaric acid: The activity of coenzyme A ligase(4CL)were significantly increased,hence the content of antioxidant secondary metabolites were increased and the accumulation of MDA in fruits were reduced.Among all the treatments,HS+PC had the best effect.At the end of storage,the firmness of fruits treated by HS+PC was significantly higher than that of other treatments and CK,the contents of TSS and TA was 9% and 63.42% higher than CK,respectively,and the rotting rate and weight loss rate were reduced by 51.21% and 26.11%,respectively.The overall effect of heat shock treatments on sweet cherry was better than that of cold shock treatments in low-temperature storage.3.In the two post-harvest storage experiments of room-temperature and low-temperature,the effects of different temperature treatments compound PC(CS+PC,HS+PC)were better than those of the corresponding single temperature treatment(CS,HS).