Involvement of peroxidase and polyphenol oxidase in mango sap-injury.
John K. S., Bhat S. G., Rao U. J. S. P.
Author Affiliation: Dept. of Biochemistry and Nutrition, Central Food Technological Research Institute, Mysore - 570 013, India.
Journal of Food Biochemistry 26 : 403-414
Abstract : Sap (latex) that oozes out from mango during harvest, upon contact with the fruit, causes dark spots (sap injury) on the peel and reduces consumer acceptance and shelf life of fruit. In this investigation, different components responsible for sap injury were identified. Mango saps from four Indian cultivars were collected and separated into aqueous and nonaqueous phases. Whole sap, aqueous phase and nonaqueous phase were tested for their ability to cause sap injury (browning) on mangoes. The nonaqueous phase caused the highest injury and the extent of injury caused by nonaqueous phases from different cultivars varied. Limonene, ocimene and ?-myrcene, the major terpenoids identified in saps of Indian cultivars, caused injury. Similar type of injury on mangoes was also caused by organic solvents. Damage on Totapuri mango fruit was significantly lower compared to other cultivars, whereas Totapuri nonaqueous phase caused injury on all other cultivars. The peel of Totapuri variety had very low level of polyphenol oxidase [catechol oxidase], peroxidase and polyphenols compared to other varieties. Thus, a clear relation was found between the peel polyphenol oxidase, peroxidase activities, the polyphenol content in the peel and the extent of injury. Further, nonaqueous phase applied on peels previously heat-treated at 95°C for 5 minutes, neither caused injury nor showed any enzyme activity. Thus, the results indicated that the terpenoid components of sap and polyphenol oxidase, peroxidase, polyphenols of peel are involved in sap injury.