Banana fruit (Musa cavendishii [Musa acuminata] AA Group cv. Sucrier) were placed in trays and held at 29-30 degreesC. Covering the trays with 'Sun wrap' polyvinyl chloride film prevented the early senescent peel spotting, typical for this cultivar. Carbon dioxide and ethylene concentrations within the packages increased, but inclusion of carbon dioxide scrubbers or ethylene absorbents, which considerably affected gas composition, had no effect on spotting. Experiments with continuous low oxygen concentrations confirmed that the effect of the package was mainly due to low oxygen. Relative humidity was higher in the packages but this had no effect on spotting. The positive effect of modified atmosphere packaging on peel spotting was accompanied by reduced in vitro phenylalanine ammonia lyase (PAL) activity in the peel, and by an increase of in vitro polyphenol oxidase (PPO; catechol oxidase) activity. We conclude that senescent spotting of banana peel requires rather high oxygen levels. It is not known which reaction becomes limiting for spotting, at low oxygen levels. Whatever the mechanism, the increase of in vitro PPO activity apparently shows an increase in potentially active protein. (C) 2003 Elsevier B.V. All rights reserved.
- phenylalanine ammonia-lyase
- polyphenol oxidase