Senescent spotting of banana peel is inhibited by modified atmosphere packaging

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

Chilling injury in mangosteen fruit

Major components of mangosteen (Garcinia mangostana L.) fruit quality include pericarp hardening, and shrinkage of both the stem and the sepals (calyx). At room temperature in South-East Asia (29±308C) the fruit remains acceptable for about 6±8.d. To determine optimum storage temperature, fruit were stored at 38, 68 and 128C (88±90% r.h.). Unacceptable chilling injury symptoms were found within 5.d at 38 and 68C. Symptoms were hardening of the pericarp, browning of the edible aril, and off-¯avour. Early pericarp hardening was not correlated with increased lignin synthesis, but elevated lignin levels preceded hardening at later stages. Storage at 128C produced acceptable levels of chilling symptoms, and therefore resulted in the longest storage life (20.d). Storage life at 128C was limited by shriveling of the calyx and stem end. Calyces and stems were dipped in various concentrations of benzyladenine (BA), gibberellic acid (GA3) and 1-naphthaleneacetic acid (NAA), either alone or combination, prior to storage at 128C. BA delayed calyx and stem shriveling during storage, thereby allowing at least 25.d of storage. It is concluded that storage of mangosteen at 3 and 68C induced unacceptable pericarp discoloration and pericarp hardening, whereas storage at 128C did not. Dipping in BA can be used to extend the storage period at 128C