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Krista C. Shellie and Robert L. Mangan

`Valencia' oranges [Citrus sinensis (L.) Osbeck] were exposed to moist, forced air (MFA) at 46, 47, or 50C for 1, 2, 3, or 4 hours to identify the maximum temperature and duration of exposure for which there was no detectable reduction in fruit quality. The flavor of oranges exposed to MFA at 47 or 50C was rated significantly inferior to that of oranges exposed to 46C. The degree minutes that accumulated in the center of the fruit between 2 and 4 hours and the maximum fruit center temperature during the heat treatment were associated with inferior fruit flavor. Oranges exposed to MFA at 46C for up to 4 hours could not be distinguished from the nonheated fruit. MFA at 46C is a promising quarantine treatment for `Valencia' oranges.

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Krista C. Shellie and Robert L. Mangan

Navel orange [Citrus sinensis (L.) Osbeck] was exposed to moist, forced air at 46 °C for up to 4.5 hours or 50 °C for 2 hours, or immersed for 3 hours in water at 46 °C. Quality attributes of heated and nonheated fruit were compared after 4 weeks of storage at 7 °C and 1 week at 23 °C. The flavor of oranges immersed in water was rated significantly inferior to fruit heated in air and fruit that were not heated. Oranges immersed in hot water also developed a higher incidence of decay during storage than oranges heated in air or nonheated control fruit. The flavor of oranges exposed to moist, forced air at 46 °C for up to 4.5 hours was rated by preference panelists as similar to nonheated controls, even though heated fruit had a significantly lower amount of titratable acidity and a higher ratio of sugar to acid. Fruit exposed to high-temperature forced air developed less decay during subsequent storage than nonheated control fruit. Texas `N33' navel oranges tolerated exposure to forced air at 46 °C for up to 4.5 hours without deleterious effects on fruit market quality.

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Krista C. Shellie and Robert L. Mangan

`Dancy' tangerines (Citrus reticulata Blanco) were harvested after color break and exposed to high-temperature forced air (HTFA) at 45C for 3.5 or 4 h to kill Mexican fruit fly [Anastrepha ludens (Loew)] larvae. Heat-treated and control fruit were stored subsequently for 2 weeks at 4C. Tangerines harvested after color break (naturally degreened) tolerated exposure to HTFA in a similar fashion as tangerines harvested before color break and degreened by postharvest exposure to ethylene. Titratable acidity (TA) was significantly lower after heat treatments. Flavor, soluble solids concentration, external appearance, incidence of decay, percent juice yield, percent weight change, and flavedo color of heat-treated fruit were not different from nonheat-treated, control fruit. Exposure to HTFA is a viable alternative to methyl bromide for disinfestation of `Dancy' tangerine.

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Krista C. Shellie, Robert L. Mangan and Sam J. Ingle

The objective of this research was to investigate whether a controlled atmosphere established inside a high temperature forced air chamber could enhance the mortality of the most heat-resistant life stage of Mexican fruit fly larvae (Anastrepha ludens Loew) and thereby reduce the amount of time grapefruit (Citrus paradisi Macf.) harvested from Mexican fruit fly-infested regions must be exposed to high-temperature forced air to achieve quarantine security. The mortality of third instar larvae treated on diet was significantly higher after exposure to 1% oxygen or 1% oxygen enriched with 20% carbon dioxide than it was in either air or air enriched with 20% oxygen. Reducing the amount of oxygen in air from 21% to 1% during forced air heating at 46°C, reduced the exposure time required for 100% kill of larvae inside artificially infested grapefruit from 5 hours to 3.5 hours. Inconsistent fruit quality results warrant further study to optimize controlled atmosphere conditions during heating. Based upon relative levels of carbon dioxide inside the grapefruit during heating, fruit respiration during heating in 1% oxygen was lower than during heating in air. Results from this research suggest that reducing the amount of oxygen in a high temperature forced air chamber during heating can reduce the amount of time fruit must be exposed to heat for quarantine security against Mexican fruit fly.

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

Early season degreened `Dancy' tangerines (Citrus reticulata Blanco) were size graded and subjected to high-temperature, moist, forced-air (HTMFA) treatments using air at 45, 46, or 48C for 0, 1, 2, 3, or 4 hours. The phytotoxic response of fruit to the beat treatments was evaluated immediately after treatment and weekly during 3 weeks of cold (4C) storage. Mortality of nonfeeding, third instar Mexican fruit fly [(Anastrepha ludens (Loew)] larvae was estimated for each time-temperature heat treatment combination in water baths that simulated the heating and cooling profiles of heat-treated fruit. Unacceptable phytotoxic symptoms, such as inferior flavor and darkened flavedo tissue, were observed when fruit was treated at 46 or 48C. Fruit heated with 45C forced moist air had flavedo color change(ΔL*)percent juice yield, soluble solids concentration, and flavor ratings that were statistically similar to ratings for unheated, control fruit. An HTMFA treatment of 3 or 4 hours at 45, 46, or 48C and subsequent cooling was sufficient to kill 100% of naked larvae in water baths. Market quality of fruit was maintained after a 4-hour HTMFA treatment at 45C, and 100% mortality of naked larvae occurred after 3 hours at 45C.