Comparative Study Of Pre-harvest Bagging With Yellow And White Bags On Fruit Quality And Soft Nose Of 'Keitt' Mango Fruit During Postharvest

‘Keitt' mango is late-maturing cultivar with a large fruit.However,the fruit is susceptible to suffer from calcium-deficient physiological diseases such as soft nose,which results in losses of fruit quality and commercial values.In this study,‘Keitt' mango fruit were bagged with yellow bags or white bags after full flowering,and then the fruit about 75%maturity stage with the similar size and coloration were harvested and stored at 25 ± 1?.In order to provide a theoretical basis for more reasonable pre-harvest bagging of mango,the difference in the incidence of soft nose,mineral elements content,storage quality,sugar metabolism and cell wall metabolism of 'Keitt' mango fruit between pre-bagging with yellow bags and white bags were investigated.The main research results were as following:(1)The incidence of soft-nose disease in mangoes bagged with yellow and white bags increased along with the process of fruit ripening,but the incidence of soft-nose disease in mangoes bagged with yellow bags was significantly lower than that with white bags during storage.At full-ripening stage(10 d),the incidence of soft-nose disease was 57.6% and 70.0%,respectively.At the same stage during storage,the firmness,peel moisture content and titratable acid(TA)content of mangoes bagged with yellow bags decreased slowly,and the soluble solid content(SSC)increased slowly,indicating that fruit bagged with yellow bags showed better storability.The SSC in white-bagged mango fruit increased rapidly,but peel moisture content and TA content were significantly lower than those in yellow-bagged mango fruit.The results suggested that bagging with yellow bags for mango fruit was beneficial to reducing the incidence of soft nose,delaying fruit ripening and maintaining fruit quality during storage.(2)The contents of N,K and Ca in the pulp of yellow-bagged mango fruit were higher than that in white-bagged mango fruit,while the contents of P and water-soluble Cawere slightly lower than that in white-bagged mango fruit.The distribution of mineral elements in yellow-bagged mango fruit was relatively balanced,but the total content of Ca was higher than that in white-bagged mango fruit.The results indicated that the yellow-bagged mango fruit could significantly increase the content of Ca element,and affect the content of other elements in fruit,which contributed to the balance of endogenous nutrients of the fruit,as compared to the fruit bagged with white bags.(3)The activities of polygalacturonase(PG),pectin methylesterase(PME)and cellulase(Cx)in yellow-bagged mango fruit increased slowly,the original pectin and cellulose contents were high,and the water-soluble pectin content increased slowly,while the activity of PG and Cx in white-bagged mango fruit was higher,the original pectin and cellulose were hydrolyzed rapidly,and the water-soluble pectin content was significantly higher than that in yellow-bagged mango fruit.The results showed that bagging with yellow bags could reduce the activities of PG and Cx,effectively delay the hydrolysis of the original pectin and cellulose,reduce the increasing rate of the water-soluble pectin content,and maintain the stability of cell wall structure,thereby delay the softening of fruit during storage,as compared to the fruit bagged with white bags.(4)The activities of amylase,acid invertase(AI),sucrose phosphate synthase(SPS)and sucrose synthase(SS)in yellow-bagged mango fruit were significantly lower than that in white-bagged mango fruit,and the starch content decreased slowly and the soluble sugar content was lower.At the same stage during storage,the activities of sugar metabolism-related enzymes in yellow-bagged mango fruit suffered soft nose were lower than that in white-bagged mango fruit suffered soft nose.The soluble sugar content in white-bagged mango fruit suffered soft nose was maintained at a high level,and the soft nose disease was more serious.The results showed that bagging with yellow bags could reduce the increasing rate of amylase,AI,SPS and SS of postharvest fruit,effectively control the decreasing rate of starch content,delay sucrose accumulation rate,and maintain the balance of sugar metabolism,which would be beneficial to reducing the incidence of soft nose and delaying the ripening process of fruit.