Postharvest rind staining in Navel oranges is aggravated by changes in storage relative humidity:: effect on respiration, ethylene production and water potential

The influence of altering storage temperature and relative humidity (RH) on the incidence of postharvest rind staining and on the physiological behaviour of Navel sweet oranges (Citrus sinensis L. Osbeck) was examined. Fruit of 'Navelina' orange stored at low (45%) or high (95%) RH did not develop rind staining upon transfer from 30 to 20 degreesC or to 12 degreesC. By contrast, in fruit stored at constant temperature (20 degreesC), transfer from 45 to 95% RH increased the incidence of rind staining, despite the rate of weight loss being similar to that of fruit for which the storage temperature was reduced. This effect was more rapid in fruit exposed for prolonged periods at low RH. A marked and transient stimulation in the respiration rate and ethylene production was observed within 12-24 h of fruit being transferred from low to high RH. Water potential (Psi(w)) in flavedo and albedo tissue was reduced by storage of the fruit at 45% RH, and the capacity for it to recover after transfer to 95% RH was more rapid in the flavedo than in the albedo and dependent on the time of storage at low RH. The influence of preharvest susceptibility on the development of the disorder during postharvest storage in 'Navelate' sweet orange was also studied. Fruit harvested from orchards with a high incidence of rind breakdown on the tree were more prone to develop rind staining after storage, had higher ethylene production and low flavedo and albedo Psi(w) at harvest than fruit harvested from orchards not affected by natural rind breakdown. Collectively, these results indicate that in Navel oranges, alteration of peel water status is a critical factor in the incidence of postharvest rind breakdown, which is also highly influenced by fruit conditions at harvest. (C) 2002 Elsevier Science B.V. All rights reserved.