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M.S. Tian, A.B. Woolf, J.H. Bowen, and I.B. Ferguson

Hot water treatments (HWTs), at a range of temperatures (43 to 55C) and durations (10 sec to 30 min), were applied to floret groups of `Shogun' broccoli (Brassica oleracea L. var italica) directly after harvest. Floret groups were then stored at 20C in the dark for 3 days. A range of optimal treatments was found in which yellowing was markedly reduced, and heat damage (water soaking and decay) did not occur. Chlorophyll fluorescence measurements indicated that in the optimum treatment that prevented yellowing the Fv/Fm ratio following HWT decreased immediately and was maintained at a constant level for the next 3 days. A further experiment examined the effect of HWT durations up to 20 min at 47C on fluorescence and yellowing. Longer durations of HWTs (>5 min) progressively reduced yellowing and the Fv/Fm ratio. From these three experiments a HWT of 47C for 7.5 min was selected as the best treatment. This treatment consistently reduced yellowing for up to 5 days. A decrease in the Fv/Fm ratio may be a useful indicator of broccoli florets response to hot water treatments.

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J.D. Hansen, M.L. Heidt, M.A. Watkins, S.R. Drake, J. Tang, and S. Wang

Quarantine regulations require domestic sweet cherries (Prunus avium) exported to Japan to be treated to control codling moth [Cydia pomonella (Lepidoptera: Tortricidae)]. The current procedure, methyl bromide fumigation, may be discontinued because of health, safety, and environmental concerns. To examine a potential alternative method, `Bing' sweet cherries were each infested with a codling moth larva, submerged in a 38 °C water bath for 6 minutes pretreatment, then exposed to various temperatures generated by radio frequency and held at that temperature for different times: 50 °C for 6 minutes, 51.6 °C for 4 minutes, 53.3 °C for 0.5 minutes, and 54.4 °C for 0.5 minutes. Insect mortality was evaluated 24 hours after treatment and fruit quality was evaluated after treatment and after 7 and 14 days of storage at 1 °C. No larvae survived at the 50 and 51.6 °C treatments. Fruit color of non-infested cherries was darkened as temperature increased. Stem color was severely impacted after 7 days of storage, even in a warm water bath of 38 °C for 6 minutes, as was fruit firmness at the same treatment. Fruit quality loss increased after 14 days of storage, compared to after 7 days of storage. The amount of pitting and bruising of cherries increased with temperature and again this increase was more evident after 14 days of storage.

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Sorkel Kadir, Michael Von Weihe, and Kassim Al-Khatib

/Fm, of ‘Cynthiana’ and ‘Vignoles’ exposed to SHS and GHS treatments at 40/35 °C and to investigate the capacity of PSII to recover from heat stress conditions. Materials and Methods Plant materials and heat treatments. Two independent

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Julio G. Loaiza-Velarde and Mikal E. Saltveit

Wounds and injuries incurred during preparation of fresh-cut lettuce (Lactuca sativa L.) stimulate phenolic metabolism, which leads to tissue browning. Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5.) is the first committed enzyme in the phenylpropanoid pathway and regulates its overall activity. Maximum activity of wound-induced PAL occurred sooner as the storage temperature increased from 0 to 25 °C, but the maximums were lower. A heat shock at 50 °C for 90 seconds protected fresh-cut lettuce tissue against browning, helped retain greenness, and decreased subsequent production of phenolics when applied either after or before wounding. Browning was reduced when the heat shock was applied up to 36 hours after wounding, while the maximum effect occurs around 6 hours before cutting. Like the heat-shock treatment, the protein synthesis inhibitor cycloheximide reduced wound-induced PAL activity, but it did not prevent tissue browning. When cycloheximide was applied in combination with heat-shock treatments, browning did not occur. Heat shocks may control tissue browning by more than just interfering with protein synthesis.

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Kate A. Nishijima, Harvey T. Chan Jr., Suzanne S. Sanxter, and Edward S. Linse

A reduced heat shock period for `Sharwil' avocado (Persea americana Mill.) before quarantine cold treatment is described. The shortened heat pretreatment period of 8 to 12 hours, rather than the originally recommended 18 hours at 38C, is effective in reducing chilling injury symptoms when the pulp is at ≤2.2C during 16 days of storage. The reduced durations and the range of pretreatment hours affords packinghouses greater efficiency and more flexibility and will reduce handling costs relative to the longer exposure.

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K.C. Shellie and R.L. Mangan

Market demand exists in the United States for fresh mango (Mangifera indica L.) fruit weighing >700 g, yet fruit of this size cannot be imported for lack of a quarantine treatment against fruit flies (Diptera: Tephritidae). Therefore, the objectives of this research were to evaluate the influence of fruit infestation method on mortality of late third instar, fruit fly larvae after fruit were immersed in hot water, and to generate dose mortality and fruit quality data for mangoes >700 g. Results suggested that artificial infestation is preferable to cage infestation because artificial infestation eliminates the direct influence of fruit weight loss on the heat dose delivered to the fruit center. Other advantages of artificial over cage infestation include: fruit maturity at treatment is similar to commercial application, mortality of untreated control fruit can be calculated, larval maturity is uniform and observable, and larvae can be placed into the slowest heating part of the fruit. Infesting with 50 rather than 25 larvae per fruit was preferred because the number of larvae placed into the fruit did not influence mortality and twice as many larvae were evaluated using the same number of fruit. The dose mortality and fruit quality data generated in this research suggest that immersion in water at 46.1 °C for 110 minutes may provide Probit 9 level quarantine security against Mexican fruit fly (Anastrepha ludens Loew) for mangoes weighing up to 900 g without adversely affecting fruit market quality.

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Allan B. Woolf, Asya Wexler, Dov Prusky, Elana Kobiler, and Susan Lurie

Effect of direct sunlight on the postharvest behavior of five avocado (Persea americana Mill.) cultivars (Ettinger, Fuerte, Hass, Horshim and Pinkerton) was examined. Probes placed 6 to 7 mm under the peel showed that the temperature an the side exposed to the sun could be as much as 15 to 20 °C higher than the temperature of shade fruit, while the nonexposed side of the fruit was ≈5 °C higher than the shade fruit. With the exception of `Ettinger', sun fruit, and especially the exposed side, were found to be most tolerant to postharvest 50 and 55 °C hot water treatments. Similarly, storage of fruit at 0 °C for between 3 to 6 weeks caused severe chilling injury to shade fruit, with less effect on sun fruit. Furthermore, there was little or no damage on the exposed side of the sun fruit. During postharvest ripening at 20 °C, sun fruit showed a delay of between 2 to 5 days in their ethylene peak compared with shade fruit. The exposed side of the sun fruit was generally firmer than the nonexposed side, and the average firmness was higher than that of shade fruit. Activities of polygalacturonase and cellulase were similar in shade and sun fruit of similar firmness. After inoculation with Colletotrichum gloeosporioides (Penz.) Penz@sacc., the appearance of lesions on sun fruit occurred 2 to 3 days after shade fruit. Levels of heat-shock proteins were examined using western blotting with antibodies for Class I and II cytoplasmic heat-shock proteins. Class I reacted with proteins from the exposed side of sun fruit and Class II with proteins from both sides of sun fruit. Thus, it is clear that preharvest exposure of fruit to the sun can result in a wide range of postharvest responses.

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Allan B. Woolf

`Hass' avocado (Persea americana Mill.) fruit were heat treated in water at 38 °C for 0 to 120 minutes, and stored at 0.5 °C for up to 28 days. After storage, fruit were ripened at 20 °C and their quality evaluated. External chilling injury (CI) developed during storage in nonheated fruit. Skin (exocarp) sectioning showed that browning developed from the base of the exocarp, and with longer storage, this browning moved outwards toward the epidermis. Longer durations of hot water treatment (HWT) progressively reduced CI; 60 minutes was the optimal duration that eliminated external CI, while best maintaining fruit quality. Concomitantly, electrolyte leakage of heated skin tissue increased ≈70% during storage, whereas electrolyte leakage of nonheated skin tissue increased ≈480% over the same period. Thus, significant protection was conferred by HWTs against low temperature damage to avocados and these effects are reflected in the morphology and physiology of the skin tissue.

Open access

Kristine M. Lang, Ajay Nair, and Alexander G. Litvin

repetition. Heat was the whole plot factor (two levels) and dark was the subplot factor (three levels) for a total number of 24 experimental units within each repetition. Each experimental unit contained 36 individual grafted plants. Heat treatments were heat

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Krista C. Shellie, Michael J. Firko, and Robert L. Mangan

Service (USDA-ARS)] for managing heat treatments. Amelia Murray (USDA-ARS) for evaluating phytotoxicity. and Mike Diaz (USDA-ARS) for evaluating insect mortalities. The cost of publishing this paper was defrayed in pan by the payment of page charges. Under