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Dangyang Ke, Elhadi Yahia, Mila Mateos, and Adel A. Kader

Changes in fermentation volatiles and enzymes were studied in preclimacteric and postclimacteric `Bartlett' pears (Pyrus communis L.) kept in air, 0.25% O2, 20% O2 + 80% CO2, or 0.25% O2 + 80% CO2 at 20C for 1, 2, or 3 days. All three atmospheres resulted in accumulation of acetaldehyde, ethanol, and ethyl acetate. The postclimacteric pears had higher activity of pyruvate decarboxylase (PDC) and higher concentrations of fermentation volatiles than those of the preclimacteric fruit. For the preclimacteric pears, the 0.25% O2 treatment dramatically increased alcohol dehydrogenase (ADH) activity, which was largely due to the enhancement of one ADH isozyme. Exposure to 20% O2 + 80% CO2 slightly increased ADH activity, but the combination of 0.25% O2 + 80% CO2 resulted in lower ADH activity than 0.25% O2 alone. For the postclimacteric pears, the three atmospheres resulted in higher PDC and ADH activities than those of air control fruit. Ethanolic fermentation in `Bartlett' pears could be induced by low O2 and/or high CO2 via 1) increased amounts of PDC and ADH; 2) PDC and ADH activation caused by decreased cytoplasmic pH; or 3) PDC and ADH activation or more rapid fermentation due to increased concentrations of their substrates (pyruvate, acetaldehyde, or NADH).

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Mark J. Arena, Otto J. Schwarz, and Willard T. Witte

Aqueous diffusates of either Salix erythroflexus (contorted willow) or Robinia pseudoacacia (black locust) were tested as a root-promoting substance on woody plants and Vigna radiata (mung bean). On 8 July 1995 water diffusates were prepared from fresh chopped terminal stems of either willow or locust (680 g) that were steeped in 4 liters of water for 24 hours. Semihardwood cuttings of Chionanthus retusus were double wounded, steeped in either willow, locust, or water for 24 hours followed by a treatment with 3.0% IBA in talc. One additional group of cuttings was treated with 3.0% IBA only. After 75 days, cuttings treated with willow diffusate and IBA produced the greatest number of roots, followed by the locust diffusate and IBA treatments. A similar test using willow diffusate and IBA on softwood cuttings of Chionanthus virginicus resulted in an 80% success rate. A modified mung bean bioassay was used to partially characterize and verify the effects of the diffusates. Diffusates were made from chopped frozen locust or willow terminal stems (10 g/300 ml H2O), stirred for 24 hours. Mung bean cuttings treated with either locust or willow diffusate (5 ml/10 ml H2O) plus 80 ppm IBA produced more roots than IBA or either diffusate alone. A dose response test showed a significant increase in rooting as concentrations increased (H2O,10%, 50%, 75%, and 100%) for both diffusates. Ethyl acetate extractions of each diffusate at pH 3.0 produced more roots than extracts at pH 7.0. A thermal stability test (20 min at 100 °C) on the diffusates showed willow maintained its root-promoting activity, while locust did not.

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Sara Simpkins, Basavaraj Girennavar, G.K. Jayaprakasha, and Bhimanagouda S. Patil

Irradiation of fruit and vegetables can potentially be used by industry as a quarantine method to contain insect pests, microorganisms, and to extend shelf life. Gamma, electron beam, and ultraviolet radiation are the most frequently used radiation techniques. These radiation treatments have an effect on bioactive compounds. Grapefruit juice contains bioactive compounds such as limonoids, flavonoids, and furocoumarins. Bioactive furocoumarins in grapefruit juice have been found to increase the bioavailability of many drugs. Bergamottin, dihydroxybergamottin, and paradisin A are major furocoumarins that are shown to inhibit the activity of CYP P450 3A4 and P-gylcoprotein, which are involved in the first pass metabolism of drugs in the gut. This results in a dose-dependent increase of the drug beyond what is intended. Furocoumarins are photoreactive compounds and will readily react to ultraviolet radiation. The effect of various doses of ultraviolet radiation was investigated on `Rio Red' and `Marsh White' grapefruit. Grapefruit juice (50 mL) was irradiated with Ultraviolet A, B, and C radiation for either 5 or 10 min. Treated and control juice was extracted with 100, 50, and 50 mL of ethyl acetate. The extract was then dried and reconstituted with methanol and filtered through a 0.4-μm PTFE membrane filter. The methanol extracts were analyzed by HPLC and the concentrations of bergamottin, dihydroxybergamottin, and paradisin A were compared for UVA, UVB, UVC, and control. This project is based upon work supported by the USDA-CSREES under Agreement USDA IFAFS # 2001 52102 02294 and USDA # 2005-34402-14401 “Designing Foods for Health” through the Vegetable & Fruit Improvement Center.

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C.B. Watkins, J.E. Manzano-Mendez, J.F. Nock, J. Zhang, and K.E. Maloney

The tolerances of strawberry fruit to postharvest CO2 treatments is an important factor in assessing their potential for extended storage and marketing, but little information on variation among cultivars is available. We have assessed differences in responses of seven strawberry cultivars (`Annapolis', `Earliglow', `Kent', `Honeoye', `Cavendish', `Jewel', and `Governor Simcoe') to high-CO2 atmospheres. Fruit were harvested at the orange or white tip stage of ripeness, kept in air, or 20% CO2 (in air), and sampled after 1, 2, or 7 days for analysis of firmness, color, and volatile concentrations. Berries from each cultivar were collected on three separate harvest dates. Flesh firmness measurements of all cultivars tested were higher when treated with high CO2, but the degree of firming was affected by cultivar and assessment time. For example, firmness of `Annapolis', `Earliglow', `Honeoye', and `Jewel' was consistently enhanced by CO2, compared with air, during storage. In contrast, firmness of `Kent' was not affected by treatment after 1 day of storage and benefits were relatively slight at each subsequent removal. Red color development of the fruits was affected by cultivar and treatment period, but not by CO2 treatment. Volatile accumulation varied greatly among cultivars. `Annapolis' for example, appears very tolerant of high-CO2 treatment levels as indicated by low accumulations of ethanol, acetaldehyde, and ethyl acetate in the fruit. In contrast, `Kent' and `Governor Simcoe' accumulated large amounts of these compounds. This study indicates that differences in cultivar responses to CO2 should be considered by growers planning to store fruit under these conditions to extend marketing options. Research supported in part by the North American Strawberry Growers Association.

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Robert A. Saftner

The effects of harvest-applied coating and shrink-wrap polymeric film treatments of apples [Malus ×domestica Borkh. `Gala' and Mansf. `Golden Delicious'] on volatile levels, quality attributes, respiration, and internal atmospheres after storage at 0 °C for 1 to 6 months, and during subsequent shelf life at 20 °C were investigated. Over 30 volatiles were detected, most of the identified volatiles were esters, the rest were alcohols, aldehydes, a ketone and a sesquiterpene. Shellac- and wax-based fruit coatings transiently inhibited total volatile levels in `Golden Delicious' while not affecting those in `Gala' apples during 6 months of storage in air at 0 °C. Holding fruit at 20 °C for up to three weeks following cold storage increased volatile levels with coated and nontreated fruit having similar amounts. Only shellac-coated `Golden Delicious' apples accumulated ethanol and ethyl acetate when held at 20 °C. The shrink-wrap polymeric film treatment had no effect on fruit volatile levels during cold storage or during subsequent shelf life at 20 °C. Coating but not film treatments reduced respiration and ethylene production rates that were observed upon transferring the fruit to 20 °C. Internal CO2 and ethylene levels increased and O2 levels decreased in coated fruit. The coating treatments led to better retention of flesh firmness in `Golden Delicious' but not `Gala' apples. Coating and film treatments reduced fresh weight loss in both cultivars during cold storage. The results suggest that harvest-applied coating and film treatments having relatively high permeability for CO2 and O2 and relatively low permeability for water vapor and fruit volatiles have potential for improving the storage and shelf-life qualities of `Gala' and `Golden Delicious' apples.

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Robert K. Prange, John M. DeLong, Peter A. Harrison, Jerry C. Leyte, and Scott D. McLean

A new chlorophyll fluorescence (F) sensor system called FIRM (fluorescence interactive response monitor) was developed that measures F at low irradiance. This system can produce a theoretical estimate of Fo at zero irradiance for which we have coined a new fluorescence term, Fα. The ability of Fα to detect fruit and vegetable low-O2 stress was tested in short-term (4-day) studies on chlorophyll-containing fruit [apple (Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.), pear (Pyrus communis L.), banana (Musa ×paradisiaca L.), kiwifruit (Actinidia deliciosa C.S. Liang & A.R. Ferguson), mango (Mangifera indica L.), and avocado (Persea americana Mill.)] and vegetables (cabbage (Brassica oleracea L. Capitata Group), green pepper (Capsicum annuum L. Grossum Group), iceberg and romaine lettuce (Lactuca sativa L.)). In all of these fruit and vegetables, Fα was able to indicate the presence of low-O2 stress. As the O2 concentration dropped below threshold values of 0 to 1.4 kPa, depending on the product, the Fα value immediately and dramatically increased. At the end of the short-term study, O2 was increased above the threshold level, whereupon Fα returned to approximately prestressed values. A 9-month study was undertaken with `Summerland McIntosh' apple fruit to determine if storing the fruit at 0.9 kPa O2, the estimated low O2 threshold value determined from Fα, would benefit or damage fruit quality, compared with threshold + 0.3 kPa (1.2 kPa O2) and the lowest recommended CA (1.5 kPa O2). After 9 months, the threshold treatment (0.9 kPa) had the highest firmness, lowest concentration of fermentation volatiles (ethanol, acetaldehyde, ethyl acetate) and lowest total disorders. Sensory rating for off-flavor, flavor and preference indicated no discernible differences among the three treatments.

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Ji Heun Hong and Ken Gross

Fresh-cut produce continues to be a rapidly growing industry. However, there is little information available on storage conditions for many commodities, particularly for fresh-cut tomato slices. A major problem with fresh-cut tomato slices is their short shelf-life. The best method to extend shelf-life is refrigerated storage, preferably around 4 to 5 °C. Unfortunately, tomato tissue is susceptible to chilling injury at such temperatures. Experiments were conducted to compare changes in quality of slices from red tomato (Lycopersicon esculentum Mill.) fruit during storage at 5 or 10 °C under various modified-atmosphere conditions. In this study, we used the fourth uniform slice from the stem end and analyzed for various quality attributes during the storage period. At both 5 and 10 °C storage temperatures, ethylene concentration in containers sealed with Film A (oxygen transmission rate of 60.3 or 77.9 ml per hour per m2 at 1 atm and 99% relative humidity at 5 or 10 °C, respectively) was higher than that sealed with Film B (oxygen transmission rate of 87.4 or 119.4 ml per hour per m2 at 1 atm and 99% relative humidity at 5 or 10 °C, respectively), during storage. In addition, chilling injury, as measured by percent of slices showing some water soaked-areas, in containers sealed with Film B was higher than that of slices in containers sealed with Film A. The percent of visible fungal growth of slices was roughly correlated with the degree of chilling injury, as measured by the percent of slices showing some water soaked-areas. After 13 days of storage at 5 °C, slices stored in containers with a beginning atmospheric composition of 12% CO2 /1% O2 were firmer, compared to slices given the other treatments. After 9 days of storage at 10 °C, no visible fungal growth was observed on slices in containers with a beginning atmospheric composition of 12% CO2/1% O2 or 12% CO2/20% O2. However, slices in containers with a beginning atmospheric composition of air, or 4% CO2/1 or 20% O2 and 8% CO2/1 or 20% O2 did show visible signs of fungal growth at 25%, 33%, 46%, 29%, and 100% of infected slices, respectively. Slices in containers given all treatments, with the exception of 12% CO2/1% O2, had visible fungal growth after 15 days of storage at 5 °C. Slices in containers containing eight slices had less chilling injury and visible fungal growth than those containing four slices. Chilling injury of slices stored in completely enclosed plastic containers, similar to those commonly observed in grocery food stores, was over 7-fold higher than chilling injury observed in slices containers covered with Film A after 12 days of storage at 5 °C. However, there were no significant differences in the amounts of the volatiles we measured, i.e., ethanol, ethyl acetate, hexanol and hexanal, between the two container types. These results suggested that modified-atmosphere packaging storage can extend shelflife, as well as inhibit chilling injury in fresh-cut tomato slices.

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Clara Pelayo-Zaldívar, Jameleddine Ben Abda, Susan E. Ebeler, and Adel A. Kader

treatment. Among aroma compounds, esters are apparently the volatiles most affected by CO 2 -enriched atmospheres. The levels of ethyl acetate and ethyl butyrate increased over isopropyl, propyl, and butyl acetates in ‘Chandler’ strawberries at 5 °C in 50

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Weiguang Yi and Hazel Y. Wetzstein

solvents have been used, including water, ethanol, methanol, acetone, and ethyl acetate at different mixture ratios ( Areias et al., 2000 ; Durling et al., 2007 ). The efficacy of different solvents varies with species and compounds of interest. Lim and

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Simona Pinnavaia, Emilio Senesi, Anne Plotto, Jan A. Narciso, and Elizabeth A. Baldwin

other treatments, confirming the most possible precursor of this branched alcohol to be an amino acid such as l -isoleucine ( Hansen and Poll, 1993 ; Rowan et al., 1996 ). Fermentative metabolites, ethanol, acetaldehyde, and ethyl acetate