Effects of ascorbic acid on peroxidase and polyphenoloxidase activities in fresh-cut cantaloupe melon

Peroxidase (POD) and polyphenol oxidase (PPO) in minimally processed cantaloupe melon (Cucumis melo L. var. reticulatus Naud) were assayed and the effect of ascorbic acid on their respective activities during storage at 4 degreesC was determined. POD activity decreased with storage and was inhibited by ascorbate treatment. Two native electrophoretic POD bands with estimated molecular weights 240 and 170 kDa respectively were obtained. Isoelectric focusing separated six acidic POD isozymes with isoelectric points between 5.1 and 6.0, possibly subunits of the POD isozymes. PPO activity in the cantaloupe melon extract was very weak and the fruit's content of oxidizable phenolic compounds was negligible.