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Theeranuch Chantrachit and Daryl G. Richardson

Ripening bananas (color stage 5) were placed in closed jars held at 20°C. Nitrogen (99.99%, 100 ml/min) or air were flowed through the jars. SPME (Solid Phase Micro Extraction) was used for sampling dynamic headspace and analyzed by GC-MS and GC-FID. Several volatile compounds decreased with time in the nitrogen treatment. Production of isobutyl butyrate, 3-methyl-1-butanol, methyl heptanoate, pentyl acetate, and 2-pentanol which were present in air treatments, were absent in the nitrogen treatment. Ethanol rapidly increased until the last day. Off-flavors were detected by most panelists after three days of N2 treatment and off-flavors increased in the following days. Reversibility of off-flavor after exposing the bananas to air was not detected by panelists. Correlations were low between the main compounds in the nitrogen treatment and the off-flavor score.

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Valeria Sigal-Escalada and Douglas D. Archbold

Our goal was to determine how aminoethoxyvinylglycine (AVG) and 1-methylcyclopropene (MCP) interact to influence postharvest storability and volatile production of `Gala' apple. In 2004 and 2005, AVG was applied to `Gala' apple trees 4 weeks before harvest. After harvest, control and AVG-treated fruit were treated for 20 h at 30 °C with MCP, and fruit were ripened at ambient temperature immediately after harvest, after MCP treatment, or after storage at 4 °C for 6 and 12 weeks. For both seasons, control fruit reached the highest internal ethylene concentration (IEC) during ripening at ambient temperature immediately after harvest. After storage, control fruit had very low IEC in 2004, but the highest in 2005. In general, the combined treatment repressed ethylene production the most for all harvest dates and lengths of storage. AVG plus MCP-treated fruit consistently had the highest flesh firmness (FF) but also had the lowest total volatile production (TVP) by flesh or peel after 6 and 12 weeks in cold storage following both harvest dates. The activity of alcohol acyltransferase was affected by the treatments, but could not explain all the variation found in TVP. TVP was lower for flesh than peel of control and treated fruit, but feeding alcohol substrates to the fruit resulted in a significant increase in TVP, regardless of tissue type or treatment. The results indicate that the combination of AVG plus MCP maintained apple fruit FF in cold storage better than the treatments used alone, but also substantially reduced TVP. Substrate availability seemed to be the most limiting factor affecting TVP by flesh and peel of `Gala' apples treated with AVG plus MCP.

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Michael A. Jordan, Kenneth McRae, Sherry Fillmore and Willy Renderos

Volatile compounds contribute to carrot (Daucus carota) flavor. However, effects of postharvest treatments on these compounds are not defined. To characterize treatment effects, fresh carrots (cv. Sunrise) were treated with 0 or 1.0 μL/L 1-methylcyclopropene (1-MCP) at 10 °C for 16 h, then exposed to 0, 0.3, or 1.0 μL/L ozone (O3) at 10 °C for 1, 2, or 4 days, and subsequently stored at 0 °C for up to 24 weeks. Twelve terpenes were identified in the headspace over whole carrots, including dimethylstyrene (22.5%), alpha-pinene (19.1%), caryophyllene (15.8%), beta-pinene (9.1%), p-cymene (8.3%), limonene (7.7%), gamma-terpinene (6.7%), myrcene (4.7%), gamma-terpinolene (4.5%) camphene (1.0%), alpha-phellandrene (0.52%), and sabinene (0.03%). Most terpenes responded similarly to treatments and storage. Immediately after treatment with 1.0 μL/L O3 for 1, 2, or 4 days, total terpene concentrations were 45%, 85%, and 87% greater than concentrations in non-treated controls. Caryophyllene, beta-pinene, and sabinene did not increase in response to the O3 treatment unlike the other terpenes. 1-MCP reduced terpene concentrations by an average of 18%. O3 treatments also stimulated stress volatile production. Ethanol headspace concentrations were 8-, 21-, and 43-times greater than the nontreated controls immediately following treatments with 0.3 nL/L O3 for 4 days or 1.0 μL/L O3 for 2 or 4 days, respectively. However, after 8 weeks, no differences among treatments were observed. Hexanal production also was stimulated by all O3 treatments, being 2- to 11-times greater than controls immediately following treatment. 1-MCP reduced O3-stimulated ethanol and hexanal production by 23% and 8%, respectively.

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Fernando Maul, Steven A. Sargent, Elizabeth A. Baldwin and Charles Sims

`Agriset-761' and `CPT-5' tomato fruits were harvested at green stage and subsequently exposed to a postharvest exogenous ethylene-air mixture (100 ppm C2H4 at 20°C). Tomatoes with visual symptoms of ripening (breaker stage = <10% red coloration) were removed from ethylene treatment after 1, 3, and 5 days and were transferred to 20°C and 85% RH. At “table-ripe” stage (full red coloration and 4-mm fruit deformation after 5 sec@9.8N), whole fruit samples were analyzed for difference/discrimination sensory evaluations, aroma volatile profiles, and chemical composition. Flavor of fruits gassed for 1 day was rated significantly different than that of fruits gassed for 3 or 5 days (n = 25 panelists) for both cultivars. Several panelists noted the perception of “rancid” and “metallic” tastes, and “lingering” aftertaste in fruits gassed for 5 days. Chemical composition assays showed that flavor differences could be partially due to a significant increase in pH values between fruits gassed for 1 and 5 days (4.23 and 4.34, respectively for `Agriset-761') and a significant decrease in titratable acidity (0.91% and 0.73%, respectively, for `Agriset-761'; 1.04% and 0.86%, respectively, for `CPT-5'). No significant differences in soluble solids content or total sugars were found in any treatments for either cultivar. `Agriset-761' showed significant increases in the concentrations of acetone, hexanal, 2+3 methylbutanol, and a decrease in 2-isobutylthiazole, whereas, `CPT-5' fruits showed significant increases in hexanal, 2+3 methylbutanol, trans-2-heptenal, 6-methyl-5-hepten-2-one, 2-isobutylthiazole, β-ionone, geranylacetone, and a decrease is ethanol concentration. In both cultivars, these significant differences in important aroma volatile compounds could be of enormous relevance in the perception of off-flavor/off-odors.

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Yan Wang and Stanley J. Kays

The sweetpotato weevil is the single most critical insect pest of the sweetpotato worldwide. While male weevils can be lured to traps using a synthetic female pheromone, crop losses are not adequately reduced since damage is caused by the larvae arrising from eggs laid by female weevils in the storage roots. Identification of a female attractant could greatly enhance the control of the insect. The leaves and storage roots are known to emit volatiles that attract the female and in the following tests, we demonstrate that feeding by female weevils stimulates the synthesis of a volatile attractant which attracts additional females to the root. Undamaged, artificially damaged, and female weevil feeding damaged periderm were tested in dual-choice and no-choice olfactometers. Volatiles from feeding damaged roots were significantly more attractive than undamaged and artificially damaged roots. To test whether the volatile attractant was of weevil or root origin, volatiles were collected in MeCl2 after removal of the weevils and fractionated on a megabore DB-1 capillary column using a GC fitted with a TC detector. Fractions were collected from the exit port and their activity index (AI) determined using dual choice and no choice olfactometry. The active fraction was ascertained and active components identified via GC-MS.

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Richard M. Pfeil and Ralph O. Mumma

Air sampling using Tenax, a selective solid absorbent, was performed from spawning to pinning over the duration of four mushroom crops of Agaricus bisporus (Lange) Imbach (Fungi; Agricaceae). The contents of the air sampling tubes were thermally desorbed directly to a gas chromatograph-mass selective detector. In two crops 3-octanone and 1-octen3-ol were detected 12 to 13 days after spawning. These two compounds were also detected after compost was added at casing (CAC) and the ketone was present in large quantities. Air sampling of a 10-g sample of spawned compost vs. unspawned compost confirmed that these two compounds were of fungal origin. Bags of spawned compost were used to determine the effects of a CAC layer, a soybean supplement, and Spawn Mate on the volatiles released by the spawned compost. The CAC layer and the soybean supplement selectively absorbed 1-octen-3-ol and, to a lesser extent, 3-octanone. The addition of Spawn Mate to the compost at spawning did not alter the quantity or ratio of 3-octanone to 1-octen-3-ol released by the spawned compost.

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Charles F. Forney, Michael A. Jordan, Kumudini U.K.G. Nicholas and Jennifer R. DeEll

Use of volatile emissions and chlorophyll fluorescence as indicators of freezing injury were investigated for apple fruit (Malus ×domestica Borkh.). `Northern Spy' and `Delicious' apples were kept at -8.5 °C for 0, 6, or 24 h, and then at 20 °C. After 1, 2, 5, and 7 d at 20 °C, fruit were analyzed for firmness, skin and flesh browning, soluble solid content, titratable acidity, ethanol, ethyl acetate, ethylene, respiration rate, and chlorophyll fluorescence. Freezing caused skin and flesh browning and a loss of fruit firmness, which was greater in `Northern Spy' than in `Delicious'. In `Northern Spy' fruit subjected to the freezing treatments, ethanol and ethyl acetate concentrations were as much as 37- and 300-fold greater, respectively, than in control fruit. `Delicious' fruit showed similar patterns of ethanol and ethyl acetate increase, but of lower magnitude, as a result of freezing. Higher fruit respiratory quotients were associated with increased ethanol and ethyl acetate concentrations. Ethylene production and chlorophyll fluorescence of fruit were reduced by freezing.

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Xuetone Fan and James P. Mattheis

Jasmonic acid and its methyl ester (methyl jasmonate), regarded as putative plant growth regulators, are naturally occurring in higher plants and present in a variety of plant organs including apple fruit. Pre- and post-climacteric `Summer Red' apples were exposed for 12 hrs to a low concentration (25ul/4L) of atmospheric methyl jasmonate. Ethylene and volatile production were measured with GC/MS at harvest and through 15 days at 20°C after treatment. Forty eight headspace volatile compounds were identified and quantified. Results showed that methyl jasmonate effects depended on stage of fruit development. Methyl jasmonate stimulated ethylene, ester, alcohol, and acid productions in preclimacteric fruits while no significant effects were observed on postclimacteric fruits. Ketone and aldehyde volatile evolutions were not significantly affected by methyl jasmonate regardless of harvest date.

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S.D. Nelson, C. Riegel, L.H. Allen Jr., D.W. Dickson, J. Gan, S.J. Locascio and D.J. Mitchell

. We thank Arthur Hornsby and John Thomas of the Dept. of Soil and Water Sciences, Univ. of Florida, Gainesville, for lending equipment necessary for collection of volatile gas samples. We also thank Wayne Wynn, Andy Frenock, Mike Alligood, and Tom

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Steven F. Vaughn and Fred J. Eller

Internal mold of sweet and hot peppers (Capsicum spp.) is caused by the pathogen Alternaria alternata. The pepper weevil, Anthomonus eugenii Cano (Coleoptera: Curculionidae), is an important pest of peppers in the southern U.S., Mexico, and Central America, and has been implicated in the transmission of the disease. We identified several volatiles released by pepper fruit during wounding by pepper weevils, including (E)-3-hexenyl acetate, linalool, beta-ocimene, and 3,7-dimethyl-1,3,6 octatriene (homoterpene). To study the roles of these volatiles in the interaction of the plant and fungus, we determined their effect on the growth of isolated cultures of A. alternata. Fungi were unaffected by any of the compounds when exposed to individual volatiles at 1 ppm; however, a 1 ppm mixture of the four compounds significantly reduced growth. All four compounds were inhibitory individually at 10 ppm, with linalool completely inhibiting fungal growth. These results indicate a role for these volatiles in the plant's response to infection by A. alternata.