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Shravan K. Dasoju and Brian E. Whipker

Pot sunflowers (Helianthus annuus cv. `Pacino') were fertigated on ebband-fl ow benches with 100 or 200 mg·liter–1 of N to determine the influence of fertility level on plant growth and postharvest quality in interior conditions. The fertilization rates were held constant from potting until day 45, then the fertilization rates were continued, decreased, or ceased on day 45 and day 55, giving a combination of nine fertilization subtreatments. At bloom, the number of days from potting to flowering, plant height, plant diameter, flower diameter were recorded, and the root medium of five replicates per treatment were analyzed to determine the nutrient status. Five replicates of each treatments also were moved into interior conditions with artificial lighting and were graded 5, 10, and 15 days after moving to evaluate the postharvest quality. There was no significant difference among fertilizer treatments for the number of days to flower, plant height, or flower diameter. Plants fertilized with 100 mg·liter–1 N from potting until day 45, in combination with a ceasing of fertilization on day 55, had significantly better plant grades when compared to plants grown with 200 mg·liter–1 N. Plants fertigated with 100 mg·liter–1 N also had a longer postharvest life and the number of days before the flowers wilted were significantly longer. Good-quality plants with longer postharvest life were produced with 100 mg·liter–1 N and by terminating fertilization 55 days after potting.

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Adel A. Kader

Biological factors involved in deterioration of fresh horticultural perishables include respiration rate; ethylene production and action; compositional changes associated with color, texture, flavor (taste and aroma), and nutritional quality; growth and development; transpiration; physiological breakdown; physical damage; and pathological breakdown. There are many opportunities to modify these inherent factors and to develop genotypes that have lower respiration and ethylene production rates, less sensitivity to ethylene, slower softening rate, improved flavor quality, enhanced nutritional quality (vitamins, minerals, dietary fiber, and phytonutrients including carotenoids and polyphenols), reduced browning potential, decreased susceptibility to chilling injury, and increased resistance to postharvest decay-causing pathogens. In some cases the goals may be contradictory, such as lowering phenolic content and activities of phenylalanine ammonialyase and/or polyphenoloxidase to reduce browning potential vs. increasing polyphenols as antioxidants with positive effects on human health. Another example is reducing ethylene production vs. increasing flavor volatiles production in fruits. Overall, priority should be given to attaining and maintaining good flavor and nutritional quality to meet consumer demands. Extension of postharvest life should be based on flavor and texture rather than appearance only. Introducing resistance to physiological disorders and/or decay-causing pathogens will reduce the use of postharvest fungicides and other chemicals by the produce industry. Changes in surface structure of some commodities can help in reducing microbial contamination, which is a very important safety factor. It is not likely that biotechnology-based changes in fresh flowers, fruits, and vegetables will lessen the importance of careful and expedited handling, proper temperature and relative humidity maintenance, and effective sanitation procedures throughout the postharvest handling system.

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José M. García, Cayetano Aguilera, and Antonia M. Jiménez

Strawberries (Fragaria × ananassa Duch. `Tudla') were inoculated with gray mold conidia (Botrytis cinerea Pers.) and were subjected to postharvest heat treatment by dipping in water at various temperatures for 15 min. Heat treatment delayed Botrytis proliferation, but using dips at ≥48C caused fruit to soften and develop an atypical pink pigmentation. Fruit treated at 44 or 46C showed the best retention of firmness and maintained initial quality, developing neither an off-color nor an off-flavor.

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Charles A. McClurg

Commercial producers of pumpkin (Cucurbita pepo) in the Mid-Atlantic region frequently experience losses from the fungal diseases powdery mildew (Erysiphe cichoracearum) and black rot (Didymella bryoniae). In addition to loss of fruit size in some cultivars, the diseases can result in poor-quality handles (fruit stems) and preand postharvest decay. Since the pumpkins are grown for fresh market ornamental use, their appearance, size, and quality are important in marketing strategies. Applications of recommended fungicides during the growing season, although costly, reduce losses in fruit size and quality from fungal pathogens. Subsequent storage studies have documented reduced losses and maintenance of handle quality of pumpkins treated with fungicides during the growing season. This suggests that those who want or need to store pumpkins prior to sale can evaluate costs and benefits of the program. Producers can also choose cultivars that are better suited to storage if fungicides will not be used.

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C. Chen, R.J. Roseberg, D. Sugar, and J.S. Selker

A study was undertaken to determine if microsprinkler irrigation (MI) can provide sufficient water and produce similar yield and quality of pear (Pyrus communis L.) fruit as flood irrigation (FI) in a cracking (shrinking-swelling) clay soil. Soil water content and fruit quality attributes were measured under MI and FI in 2 years. Water potential of the upper 120 cm (47 inches) of soil was maintained at 0.1 to 0.3 MPa (14.5 to 43.5 lb/inch2) through most of the growing season in both MI and FI treatments. MI and FI treatments did not differ in their effect on fruit size, yield, or firmness decline during cold storage. No consistent effect on fruit susceptibility postharvest fungal decay related to irrigation treatment was observed. MI has the potential to reduce chemical and water movement to groundwater, while providing sufficient water to produce satisfactory yield and fruit quality in a cracking clay soil.

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Victorine Alleyne and John R. Clark

An investigation was conducted in 1994 and 1995 to evaluate the effect of N rate and timing of application on postharvest performance of `Arapaho' thornless blackberry fruit. Treatments were 0 kg N/ha, 56 kg N/ha, 112 kg N/ha single application, and 112 kg N/ha split application. The N source was ammonium nitrate. Fruit samples were hand-harvested and stored for 0–8 days. In general, `Arapaho' fruit quality was not affected by N applications. Increasing N rates increased soluble solids content but had no effect on pH, titratable acidity, sugar: acid ratio, total solids, firmness, and weight loss. Nitrogen applications increased fruit N content.

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Jennifer R. DeEll and Robert K. Prange

Postharvest quality and sensory attributes of organically and conventionally grown `McIntosh' and `Cortland' apples (Malus domestica Borkh.) stored at 3C in ambient air or in controlled atmospheres were evaluated. Organically grown apples had higher soluble solids concentration than conventionally grown apples, while there were no significant differences in firmness or titratable acids content. Organically grown `McIntosh' were perceived by sensory panelists as firmer than conventionally grown `McIntosh' at harvest but not after storage, which may have been due to maturity differences. No significant differences were perceived in juiciness, sweetness, tartness, and off-flavor of apples at harvest or after storage.

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Hugo Ramirez, Mary Torcates, Jose Perez, Josefina Rodriguez, and Marin E. Perez

149 POSTER SESSION 6D (Abstr. 354–370) Postharvest Physiology–Vegetables

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Chien Y. Wang

Mature leaves of kale (Brassica oleracea L., Alboglabra group) and collard (Brassica oleracea L., Acephala group), and Brussels sprouts (Brassica oleracea L., Gemmifera group) were heated by moist air at 40, 45, 50, or 55 °C for durations of 0, 30, 60, or 90 minutes. Heating of kale at 45 °C for 30 minutes was effective in maintaining better postharvest quality, delaying yellowing, and reducing losses of sugars and organic acids during subsequent storage at 15 °C. Exposure of collard at 40 °C for 60 minutes also delayed yellowing and maintained turgidity of the leaves. Other treatments were either less beneficial, not effective, or caused injury. Heat injury occurred when temperature and duration exceeded the tolerance levels. In some cases, heat-injured tissues remained green but developed fungal infection. Heat treatments had no measurable effects on the rate of senescence or storage quality of Brussels sprouts.

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Chien Y. Wang

Mature leaves of kale (Brassica oleracea L., Alboglabra group) and collard (Brassica oleracea L., Acephala group), and Brussels sprouts (Brassica oleracea L., Gemmifera group) were heated by moist air at 40, 45, 50, or 55 °C for durations of 0, 30, 60, or 90 minutes. Heating of kale at 45 °C for 30 minutes was effective in maintaining better postharvest quality, delaying yellowing, and reducing losses of sugars and organic acids during subsequent storage at 15 °C. Exposure of collard at 40 °C for 60 minutes also delayed yellowing and maintained turgidity of the leaves. Other treatments were either less beneficial, not effective, or caused injury. Heat injury occurred when temperature and duration exceeded the tolerance levels. In some cases, heat-injured tissues remained green but developed fungal infection. Heat treatments had no measurable effects on the rate of senescence or storage quality of Brussels sprouts.