Study On Effect Of Reduced Pressure Pretreatment Combined With Chkosan Coating On Postharvest Strawberry Preservation

Strawberries are widely culticated in China and are very nutritious,sweet and tasty,and are loved by consumers of all ages.However,because of its delicate texture,it is highly susceptible to damage during postharvest storage.It can also lead to rot and spoilage of strawberries during post-harvest storage due to pathogenic infestation.Therefore,post-harvest storage and preservation of strawberries has always been an urgent problem.In this experiment,post-harvest strawberries were treated in five different ways（chitosan coating treatment（CTS）,reduced pressure pretreatment（RP）,chitosan coated followed by reduced pressure pretreatment（CR）,reduced pressure pretreatment followed by chitosan coated treatment（RC）and control group（CK））respectively.By comparing the cell wall metabolism,reactive oxygen metabolism,antioxidation of active ingredients and changes in aroma components of strawberries after different treatments,we sought the best way to preserve strawberry freshness and explored the effect of reduced pressure pretreatment and chitosan coating on strawberry preservastion,to provide reference for the postharvest storage and preservation of strawberries.The results are as follows.（1）The effect of reduced pressure pretreatment in combination with chitosan coating on the cell wall metabolism of strawberries in postharvest storage was investigated.At the 12th day of storage,the protopectin content of the RC group was 19%higher than that of the CK group,reached 0.146%.It also retarded the degradation of cellulose in RC group during storage.Compared with the other groups,the activities of Cx,PME,β-Glu,PG were obviously lower in the RC group.On day 12 of storage,strawberry hardness was 25%higher in the RC group than in the CK group.（2）We studied the effect of reduced pressure pretreatment in combination with chitosan coating on the metabolism of reactive oxygen species in strawberries during storage.The activities of POD,CAT,APX and SOD were all at relatively high levels in the strawberry of RC group by our results,which helped to improve the metabolism of reactive oxygen during storage.The reduced pressure pretreatment combined with chitosan coating could better inhibit the production of ROS(O₂^·-,H₂O₂),hence reducing the production of MDA.At the 10th day,the content of MDA in RC group was 61.78%of that in CK group.（3）The effect of reduced pressure pretreatment in combination with chitosan coating on the bioactive components and antioxidant properties of strawberries during postharvest storage was investigated.Reduced pressure pretreatment combined with chitosan coating first can maintain the content of anthocyanins,polyphenols,flavonoids and reduced ascorbic acid in strawberries during storage.The anthocyanin content of the RC group was 13.76%higher than that of the CK group at the 8th day of storage.At the last day of storage,the total reducing power of the RC group was 40.91%higher than that of the CK group.（4）The effect of reduced pressure pretreatment in combination with chitosan coating on the aroma composition of strawberries during postharvest storage was investigated.The aroma composition of strawberries in postharvest storage was examined by e-nose and GC-MS.The results by the e-nose showed that the reduce pressure pertreatment combined with chitosan coating could better maintain the aroma composition of the strawberry during storage.The aroma composition of post-harvest strawberries was analysed by GC-MS and the main aroma components were found to be esters and alcohols during storage.Through PCA analysis,it was found that the reduced pressure pretreatment combined with chitosan coating treatment on 10th day of storage reduced the loss of aroma components during storage and allowed for better maintenance of strawberry quality.