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Raymond G. McGuire

The market quality and condition of grapefruit (Citrus paradisi Macf.) were compared after three heat treatments for quarantine control of Caribbean fruit flies [Anastrepha suspensa (Loew)]. Treatment by forced air at 48C for 3 hours was compared with immersions in water at either a constant 48C for 2 hours or with a gradual increase to 48C lasting 3 hours. The immersion at a constant 48C significantly increased weight loss and promoted injury and decay while reducing firmness and color intensity after 4 weeks of storage. By more slowly heating fruit in the gradient water immersion, weight, firmness, and natural color were retained, and injury was substantially reduced, but the incidence of decay remained high. No loss in quality resulted from treatment by forced hot air. These heat treatments had little effect on juice characteristics, although acidity was slightly reduced by each method of application. In taste tests, juice from fruit treated in water that was gradually raised to 48C was preferred over that of fruit treated at a constant 48C.

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W.R. Miller and R.E. McDonald

Carambolas (Averrhoa carambola L.) require quarantine treatment for control of the Caribbean fruit fly (Anastrepha suspensa Loew) (CFF) prior to shipment to certain domestic and export markets. Low-dose irradiation, ≤1.0 kGy, is effective for sterilizing CFF and other fruit flies; however, carambolas are susceptible to irradiation-induced peel injury. Low-dose gamma irradiation treatment generally reduced fruit quality, but the effects were mitigated by packaging carambola fruit in “clamshell” polystyrene containers, rather than conventional fiberboard boxes, prior to treatment. Use of clamshell containers reduced peel pitting, stem-end breakdown, shriveling, and loss of mass after storage for 14 days at 5 or 7 °C. In addition, fruit held in clamshell containers were firmer, with slightly less green peel, and had lower total soluble solids, but the flavor was not quite as good as that of fruit stored in fiberboard boxes. There was no difference in the mastication texture or acidity of fruit by package type at final storage. Packing carambolas in clamshell containers increased their tolerance to irradiation-induced peel disorders and improved the potential for usage of low-dose irradiation for quarantine treatment.

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W.R. Miller, R.E. McDonald, G. Hallman, and J.L. Sharp

Experimental vapor heat (VH) tests [43.5C for 5 hours, 1009” relative humidity (RH)] were conducted to determine treatment effects to freshly harvested Florida grapefruit (Citrus paradisi Macf.). VH treatment reduced peel pitting 5-fold compared to control fruit after 5 weeks of storage (4 weeks at 10C + 1 week at 21C) and did not cause peel discoloration or rind breakdown. There was no difference in volume between treated and nontreated fruit after 1 week of storage or in weight loss after 5 weeks. Also, peel color, total soluble solids concentration, acidity, and pH were not affected by VH treatment. Fruit were slightly less firm after VH treatment and remained less firm throughout storage, compared with control fruit. The VH treatment tested is a potentially viable alternative quarantine treatment for control of the Caribbean fruit fly [Anastrepha suspensa (Loew)] because it is not phytotoxic to grapefruit and has been reported effective for disinfestation of this pest in grapefruit.

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Thomas L. Davenport, Thomas L. White, and Stanley P. Burg

U.S. regulations prevent importation of fresh horticultural commodities that have not received an approved quarantine treatment assuring 99.999% (Probit 9) mortality of potentially invasive insect pests. Because imported mangoes (Mangifera indica) are likely to be infested by the caribbean fruit fly (Anastrepha suspensa) and other tropical fruit flies in the Americas, such as the mexican fruit fly (A. ludens), guava fruit fly (A. striata), inga fruit fly (A. distincta), south american fruit fly (A. fraterculus), sapote fruit fly (A. serpentina), and the west indian fruit fly (A. obliqua), they must be hot-water treated prior to shipment in order to satisfy quarantine requirement. Hot water treatment often damages the fruit, especially if it is not fully mature. Hypobaric [low pressure (LP)] intermodal shipping containers developed by the VacuFresh Corp. preserve fresh commodities, such as horticulturally mature mangoes, far longer than is possible using other technologies. We tested the ability of caribbean fruit fly eggs and larvae to survive simulated optimal hypobaric conditions for shipment of mangoes [15 and 20 mm mercury (Hg), ≥98% relative humidity, 13 °C (the lowest, safe nonchilling temperature)]. Caribbean fruit fly eggs or larvae were maintained on agar media, flushed with one air change per hour at the storage pressure, and shielded with Mylar to prevent radiant heat uptake and limit evaporative cooling. Nearly 98% of the eggs and larvae were killed within 1 week at 15 and 20 mm Hg in nine replicated experiments. All eggs were killed by 11 days with a predicted kill of 99.999% of the eggs by 9.4 days in 15 mm Hg and 10.6 days in 20 mm Hg LP (based on Probit 9 statistical analysis), whereas a substantial number of eggs survived to 14 days at atmospheric pressure (760 mm Hg). Shipment of fresh produce using this technology promises to provide quarantine control while preserving the freshness of fully mature tropical fruits and vegetables.

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Raymond G. McGuire

In separate treatments, fruit of Litchi chinensis Sonn. were subjected to 15 days at 1.1 °C or to gamma irradiation from a 60Co source at dosages of 100, 200, or 300 Gy. Cold-treated `Mauritius' fruit lost some color intensity externally and internally, and the pale flesh had a greener hue. The pericarp of `Brewster' fruit was injured to a greater extent by cold treatment than that of `Mauritius', and the pulp of treated fruit had lower concentrations of acids and soluble solids. Cold treatment increased decay susceptibility of both cultivars. `Mauritius' fruit were also more susceptible to decay following irradiation at 300 Gy and 6 days of storage at 5 °C. Both cultivars lost firmness after this treatment. The pericarp of irradiated `Mauritius' fruit became more orange, whereas the flesh of both cultivars became greener. Irradiated `Brewster' fruit were less acidic and contained less soluble solids, but sensory evaluations could not differentiate between irradiated and nontreated fruit regardless of cultivar. Loss of quality was minimal with either cold or irradiation treatment, and both should be acceptable for lychees requiring quarantine treatment for eradication of exotic pests.

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Raymond G. McGuire

Immersion of guavas (Psidium guajava L.) for 35 min in water at 46.1 ± 0.2 °C slowed softening, sweetening, and color development of fruit and delayed ripening by 2 days. Heat treatment also increased susceptibility to chilling injury, decay, and weight loss in storage, but overall loss of quality was minimal. Waxing fruit within 90 min of heat treatment exacerbated chilling injury, further delayed ripening with a concomitant increase in the percentage of fruit not ripening, and caused fruit to remain greener. Waxed fruit had a lower acidity and soluble solids concentration and did not appear to ripen normally. Although heating did not appreciably affect the percentage of fruit that failed to ripen, the combination of heating and nearly immediate waxing increased the proportion not ripening to 45%. Heat and wax treatments, alone or in combination, caused CO2 levels to increase significantly before the initiation of ripening, but waxing also reduced the O2 content of fruit at this time. Before ripening, O2 levels were inversely correlated (r ≤ – 0.950) with injury, firmness, date and percentage of fruit ripening, and pH and directly correlated (r ≥ 0.950) with peel color and the concentration of acids and sugars in the pulp. Delaying the waxing of heat-treated guavas or reconditioning them for 24 h at 20 °C before cold storage promoted normal ripening and helped to maintain the quality of heat-treated fruit.

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Michael K. Hennessey, Robert J. Knight Jr., and Raymond J. Schnell

Seventeen avocado selections from the U.S. Dept. of Agriculture Miami National Clonal Germplasm Repository were bioassayed for antibiosis to Caribbean fruit fly eggs and larvae. Two colony-reared strains of flies were used. Fourteen of the selections did not support any development of immature stages to the adult stage. The results support the contention that highly resistant cultivars would not pose a high risk of spreading Caribbean fruit fly to foreign markets even without postharvest disinfestation treatment.

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W.R. Miller and R.E. McDonald

Carambolas (Averrhoa carambola L.) must be treated with an approved insect quarantine procedure such as cold treatment before shipment to certain markets. Condition and quality of mature-green (MG) and slightly yellow (SY) fruit were determined after they were: 1) treated with ethylene at 0.1 ml·L-1 for 48 hours (C2H4), 2) subjected to cold treatment (CT) at 1 °C for 15 days, and 3) held in storage at 5 °C for 7 days plus 3 days at 15 °C. Ethylene-treated fruit were softer and yellowness was enhanced compared with non-C2H4-treated fruit. MG fruit were firmer and lost more mass following CT and storage than SY fruit. C2H4 treatment increased the severity of peel scald, stem-end breakdown (SEB), and fin browning but had no effect on pitting. CT increased the severity of scald and pitting, and the severity of SEB, but did not affect fin browning. Peel scald, pitting, SEB, and fin browning were more severe in MG than in SY fruit at the final evaluation. C2H4-treated fruit had lower total soluble solids concentration, higher titratable acidity and pH, and a less preferred flavor and texture than control fruit. We conclude that carambola fruit should be selected at harvest at the slight-yellow stage (3% to 25% of surface area) instead of at the mature-green stage. Fruit to be cold-stored should not be C2H4 treated due to enhanced mold development and severity of SEB.

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Raymond G. McGuire and William F. Reeder

Early, mid-, and late-season grapefruit (Citrus paradisi Macf.) were treated with hot air at 46, 48, and 50C for 3, 5, or 7 hours to determine the effects of time and temperature on market quality. Early and late-season fruit were more easily' damaged by the higher temperatures than midseason fruit. Increased times at the lower temperatures had less of a deleterious effect on weight loss, loss of firmness and color, and susceptibility to scalding injury and fungal decay than did shorter times at the higher temperatures. Nevertheless, regression equations predicted that 3 hours at 48C or 2 hours at 49C would not adversely affec: market quality of early and midseason fruit. The suitability of these equations was verified through taste tests of Juice. It may not be possible, however, to raise the treatment temperature for late-season fruit above 47.5C without damaging the quality of juice from these fruit.

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W.R. Miller, R.E. McDonald, and J.L. Sharp

Freshly harvested mangos (Mangifera indica L.) treated with forced air at 51.5C for 125 minutes then stored for 1, 2, or 3 weeks at 12C, followed by 21C until soft-ripe, were compared with nontreated fruit for quality changes. Treated fruit lost 1.0% more fresh weight than nontreated fruit and deveoped trace amounts of peel pitting. Total soluble solids concentrations for treated and nontreated fruit were similar (≈q3%), as was peel color at the soft-ripe stage. Treated fruit generally reached the soft-ripe stage ≈q day earlier than nontreated fruit regardless of storage duration and had a lower incidence and severity of stem-end rot and anthracnose. The trace of pitting on treated fruit likely will not influence consumer acceptance.