Permeability to the postharvest fumigants ethylene dibromide (EDB) and methyl bromide (MB) varied among 10 plastic films tested on grapefruit (EDB) and oranges (MB). Permeability was determined by comparing fumigant residue levels in fumigated film-wrapped citrus fruit and fumigated nonwrapped fruit. Some films restricted passage of the fumigants to the fruit, and residue levels in fruit wrapped with these films were lower than in fumigated, nonwrapped fruit. Residue levels in fruit wrapped with other films were equal to those in fumigated, nonwrapped fruit and these films were judged to be highly permeable to the fumigants. EDB and MB residues were slightly higher in fruit wrapped with three of the films than those in nonwrapped fruit, indicating that these films were slightly less permeable to EDB and MB than to other films tested, and also that desorption of the fumigants from the fruit during post-fumigation aeration was slowed by these three films. The permeability of flexible polymer films to fumigants such as EDB and MB should be a prime consideration when selecting films for wrapping citrus fruit in quarantine situations.
Brussels sprouts (Brassica oleracea L., Group gemmifera) were stored 2, 3, or 4 weeks at 2.5°, 5°, or 7.5°C with 0.5%, 1%, 2%, 4%, or 21% O2, or in the following combinations of % O2/%CO2: 1/10, 2/10, or 20/10. Storage was followed by 2 or 3 days of aeration at 10°. Low O2 levels reduced the rate of CO2 production relative to that in air, but rates were similar among the low O2 levels. Ethylene production was low at 2.5° and 5° in all atmospheres, but at 7.5° it was 20% to 170% higher in air than in low O2. Ethylene production was virtually stopped during exposure to high CO2, but increased dramatically during aeration. Since low O2 levels retarded yellowing and 10% CO2 retarded decay development, the combinations of low O2/high CO2 effectively extended the storage life of the sprouts at 5° and 7.5°. The beneficial effect of CA storage was still evident after return of the samples to normal air. The sprouts retained good appearance for 4 weeks at 2.5° whether stored in CA or in air. Storage in 0.5% O2 occasionally induced a reddish-tan discoloration of the heart leaves and frequently an extremely bitter flavor in the nongreen portion of the sprouts. None of the atmosphere modifications appreciably affected either the tissue pH or texture of the sprouts.
Commercially packed lemons (Citrus limon (L.) Burm.), grapefruit (C. paradisi Macfayden) and oranges (C. sinensis (L.) Osbeck) from CA and AZ were fumigated in corrugated fiberboard shipping boxes with methyl bromide (MB) at doses efficacious for controlling various postharvest insect pests. Fruit developed no rind injury when fumigated at 24 or 32 g MB/m3 for 2 hr at 21C. At 40 g MB fruit developed slight to moderate peel injury, and sometimes there were more decayed fruit. More rind injury developed at 48 gm MB, the injury was more severe, and there were more decays. Curing fruit for 3-4 days at 15-20C before fumigation, and extending the aeration period after fumigation from a few hours to 1 or 3 days reduced fruit injury. Early-season fruit were not injured as severely as late-season fruit. Lemons picked with green-colored peel but fumigated after they turned yellow (by holding at 13C for 4-10 weeks to degreen) were not injured as much as silver or yellow lemons.
Two natural cytokinins, zeatin and dihydrozeatin, were effective in preserving broccoli appearance and chlorophyll content. Single treatments with 100 ppm aqueous solutions of the 2 compounds, followed by storage at 13°C, permitted storage life of 5 days for zeatin- and 4 days for dihydrozeatin-treated samples of broccoli. Repeated treatments with these compounds increased broccoli storage life to 6 days at 13°C, approaching the apparently limiting value of 7 days conferred by the synthetic cytokinin, 6-benzylamino purine (25 ppm). Broccoli without cytokinin treatment remained salable for only 2 days at 13°C. Visual scores for color were linearly related to chlorophyll concentration.
Permeability to the postharvest fumigant hydrogen cyanide (HCN) varied markedly among 13 plastic film-wrapping materials. Permeability was determined by comparing California red scale [Aonidiella aurantii (Maskell)] (CRS) surviving fumigation on film-wrapped and nonwrapped, insect-infested, fruit. HCN transmission rates for several films also were determined by a permeation cell technique. Some films partially restricted passage of the fumigant to the fruit and CRS survival was high, while permeability of other films differed little from unrestricted exposure on nonwrapped fruit and CRS survival was low. For films with low permeability to HCN, increasing the HCN concentration or the length of fumigation time are possible methods of increasing the amount of HCN that penetrates to the fruit for control of quarantined insects. The permeability of film wrapping materials to fumigants should be a prime consideration when selecting films for wrapping citrus fruit in quarantine situations.