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- Author or Editor: B. Shapiro x
The marked extension of life of citrus fruit by individual seal-packaging has attracted both basic and commercial interest (5). Delayed physiological deterioration by seal packaging was related to the alleviation of water stress of the harvested fruit (10). A risk from this technique is the possibility that decay might be enhanced by the water-saturated atmosphere of the sealed fruit (5). Although most reports do not describe any marked effect on decay, several noted that the percent decay of ‘Shamouti’ and ‘Valencia’ oranges was lightly increased by seal-packaging (5). This increase could be a function of time, since the storage life of sealed fruit is longer than that of nonsealed fruit (5, 20). Sealing of citrus fruit increased stem-end rot in general and Alternaria rot in particular (5). However, this type of decay usually requires 8 weeks for incubation, longer than fruit are usually kept in sealed packages. The major pathogen causing decay of citrus is still the green mold Penicillium digitatum Sacc. (20).
The physiological changes occurring in green and red bell pepper fruit (Capsicum annuum L. ‘Maor’) before and after harvest were investigated. Red pepper at harvest was less firm and had lower water potential, lower insoluble pectins, and higher water-soluble pectins than green bell pepper. However, the changes occurring in both types of peppers after harvest were similar. Postharvest weight loss was accompanied by a decrease in firmness, decrease in water potential, decrease in insoluble pectin, and an increase in soluble pectin in the cell wall. The production of CO2 showed that there was a slight decrease and a significant but small increase of ethylene after harvest. If weight loss was retarded by holding pepper in a water-saturated atmosphere, then all of these physiological changes were prevented or markedly slowed. It appears that water stress hastens and possibly triggers the onset of senescence in harvested bell pepper fruit.
Curing of sealed lemons of normal and decay-prone types [Citrus limon (L.) Burm.f] and of sealed Goliath pomelo [Citrus grandis (L.) Osbeck] inhibited postharvest decay without deleterious effects on fruit quality and prevented the development of Penicillium digitatum on inoculated fruit. Curing of nonsealed fruit was less effective in reducing decay than curing sealed fruit and caused prohibitive weight loss, shrinkage, and softening. Curing of sealed and waxed ‘Shamouti’ and ‘Valencia’ oranges (C. sinensis), in comparison to only sealed fruit, resulted in some CO2 injury of the peel and off-flavor.
Conventional degreening of fruits of lemon [Citrus limon (L.) Burm f.] by ethylene gas or treating with the ethylene-releasing agents (2-chloroethyl) phosphonic acid (ethephon) or 2-chloroethyl-tris(2-methoxyethoxy)silane, aggravates the development of various blemishes resulting, at times, in a loss of more than half of the fruit. Seal-packaging of lemons in 10 μm-thick film of high-density polyethylene (HDPE) markedly inhibited the development of blemishes. After 3 weeks’ storage, fruit commercially degreened with ethylene was 19.8 % blemished when unpackaged and 6.3% blemished when sealed in HDPE. Furthermore, this treatment delayed deterioration of fruit for a period longer than 6 months, much beyond that required for marketing. Spoilage resulting from blemishes, decay, softening, or overripe-coloration was much lower in sealed than in the non-sealed fruit. The combination of treatment with ethylene-releasing agents and HDPE seal-packaging permits degreening of lemons.
Seal packaging of orange [Citrus sinensis (L.) Osbeck cvs. Valencia and Shamouti], grapefruit (Citrus paradisi Macf. cv. Marsh) and lemons (Citrus limon Burnt, f. cv. Eureka) with high-density polyethylene (HOPE) film (0.01 mm in thickness) delayed softening and inhibited weight loss and deformation of the fruit more than cooling. Sealed fruit at 20°C and 85% relative humidity (RH) had better appearance and were firmer than non-sealed fruit at their lowest temperature possible without chilling injury and 85–90% RH. HOPE seal-packaging also inhibited chilling injury of grapefruit and lemons stored at 5° and 2°C, respectively. The C02 content of grapefruit was unaffected by seal-packaging, hut it was lower at cooler temperatures. Decay of citrus fruit depended more on the storage temperature than on the type of packaging. However, in storage up to 1 month, no significant difference was found in most experiments in decay percentage between orange, grapefruit, and lemon sealed with HOPE and stored in a packing house (13 to 25°C), and non-sealed fruits, at the lowest temperatures possible without chilling injury of 2, 10 and 14°C, respectively.
Seal-packaging of individual fruits of ‘Shamouti’ and ‘Valencia’ oranges (Citrus sinensis L. Osbeck), grapefruit (C. paradisi Macf cv. Marsh) and lemons (C. limon Burm. f. cv. Eureka) with a film of high-density polyethylene (0.01 mm) markedly delayed their deterioration as measured by peel shrinkage, softening, deformation and loss of flavor. This film was applied to fruit that had received conventional treatments of disinfection with sodium orthophenylphenate and waxing. Sealed fruit maintained their fresh appearance more than twice as long as conventionally handled fruit. Weight loss of fruit was reduced about five-fold. Sealed fruit at 20° were firmer and lost less weight than non-sealed fruit at the lowest optimal temperature. Sealing various citrus fruits in high density polyethylene reduced both their respiratory activity and ethylene production. CO2 and O2 content in the internal atmosphere of the sealed and control fruit were similar but ethylene content was lower in the sealed fruit.
Water loss was found to be a nondestructive indicator before visible symptoms of chilling injury (CI) in cold-stored grapefruit (Citrus paradisi Macf.) and lemon (C. limon L. Burm. f.). The water-loss rate increased significantly after removing the fruit from cold storage and holding at 20C. Scanning electron microscopy revealed large cracks around the stomata. Changes in electrical conductivity of the flavedo tissues, total electrolyte leakage, and K+ or Ca2+ leakage were all inadequate predictors of CI, appearing only after CI was evident.
`Eureka' lemons [Citrus limon (L.) Burro. f.] treated for commercial storage were held for 6 months at 13C. One-half of the fruits were individually sealed in high-density polyethylene (HDPE) plastic film and half not sealed. The HDPE-seaIed lemons showed little change in the water relations characteristics, while unsealed lemons lost weight and decreased in water potential throughout the storage period. The maturity indices in the two treatments were generally similar during the first 3 months of storage, after which maturation of wrapped fruit was slower than that of the control. The overall marketable quality of the fruit was higher in HDPE-sealed lemons than in unsealed. From these results, it appears feasible to introduce seal packaging in packing lines where lemons will be placed in extended storage.