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Arthur C. Cameron, Randolph M. Beaudry, Nigel H. Banks and Mark V. Yelanich

A mathematical model was developed to characterize the interaction of fruit O2 uptake, steady-state O2 partial pressures in modified-atmosphere (MA) packages ([O2]pkg), and film permeability to O2 (Po 2) from previously published data for highbush blueberry (Vaccinium corymbosum L. `Bluecrop') fruit held between 0 and 25C. O2 uptake in nonlimiting O2 (Ro 2 max,T) and the [O2]pkg at which O2 uptake was half-maximal (K½ T) were both exponentially related to temperature. The activation energy of 02 uptake was less at lower [O2]pkg and temperature. The predicted activation energy for permeation of O2 through the film (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{E}_{\mathrm{a}}^{\mathrm{P_{\mathrm{o}_{2}}}}\) \end{document} kJ·mol-1) required to maintain close-to-optimum [O2]pkg across the range of temperatures between 0 and 25C was ≈ 60 kJ·mol-1. Packages in which diffusion was mediated through polypropylene or polyethylene would have values \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{E}_{\mathrm{a}}^{\mathrm{P_{\mathrm{o}_{2}}}}\) \end{document} of ≈ 50 and 40 kJ·mol-1, respectively, and would have correspondingly greater tendencies for [O2]pkg to decrease to excessively low levels with an increase in temperature. Packages that depend on pores for permeation would have an \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{E}_{\mathrm{a}}^{\mathrm{P_{\mathrm{o}_{2}}}}\) \end{document} of <5 kJ·mol-1. Our procedure predicted that, if allowed to attain steady-state conditions, packages with pores and optimized to 2 kPa O2 at 0C would become anaerobic with as little as a 5C increase in temperature. The results are discussed in relation to the risk of temperature abuse during handling and marketing of MA packaged fruit and strategies to avoid induction of anaerobiosis.

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W.L. Berndt and J.M. Vargas Jr.

Biological production of sulfide (S2-) in soil has been reported to depend on system redox potential and on the concentrations of available sulfate (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{SO}_{4}^{2-}\) \end{document}) and organic carbon (OC). The purpose of this laboratory study was to determine whether elemental sulfur (So) could influence redox potential and S2- production in sand used to construct putting greens. Treatment with So depressed redox potential as pe + pH, and stimulated accumulation of both free H2S and acid-soluble S2-. Organic carbon as lactate (C3H5O3Na) intensified the effects of So, primarily by influencing pH. Thus, So application could induce anaerobiosis and subsequently affect turf quality by heightening production of free hydrogen sulfide (H2S). It could also contribute to S2- accumulation possibly expressed as a black layer or blackening of the root zone.

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James Mattheis and John K. Fellman

The commercial use of modified atmosphere packaging (MAP) technology provides a means to slow the processes of ripening and senescence during storage, transport, and marketing of many fresh fruit and vegetables. The benefits of MAP and controlled atmosphere (CA) technologies for extending postharvest life of many fruit and vegetables have been recognized for many years. Although both technologies have been and continue to be extensively researched, more examples of the impacts of CA on produce quality are available in the literature and many of these reports were used in development of this review. Storage using MAP, similar to the use of CA storage, impacts most aspects of produce quality although the extent to which each quality attribute responds to CA or modified atmosphere (MA) conditions varies among commodities. Impacts of MAP and CA on flavor and aroma are dependent on the composition of the storage atmosphere, avoidance of anaerobic conditions, storage duration, and the use of fresh-cut technologies before storage.

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Hirofumi Terai, Hironobu Tsuchida, Masashi Mizuno and Noriyoshi Matsui

Tomato fruit were given a short-term (24 h) high CO2 (80%) or N2 (100%) treatment and then transferred to air storage at 20 °C. The CO2 treatment stimulated ACC oxidase activity and ethylene production, whereas the N2 treatment increased ACC content but did not increase ethylene production. Both CO2, and N2 treatments delayed ripening for one day, but fruit ripened normally. Although short-term 80% CO2, had a stimulating effect, and 100 % N2 had no effect on ethylene production, ripening was delayed slightly by both treatments. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

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Randolph M. Beaudry, Arthur C. Cameron, Ahmad Shirazi and Diana L. Dostal-Lange

Highbush blueberry (Vaccinium corymbosum L. `Bluecrop') fruit sealed in low-density polyethylene packages were incubated at 0, 5, 10, 15, 20, or 25C until O2 and CO2 levels in the package reached a steady state. A range of steady-state O2 partial pressures (1 to 18 kPa) was created by placing a range of fruit weights within packages having a constant surface area and film thickness. The steady-state O2 partial pressure in packages containing the same weight of fruit decreased as temperature increased, indicating the respiratory rate rose more rapidly (i.e., had a greater sensitivity to temperature) than O2 transmission through the film. Steady-state O2 and CO2 partial pressures were used to calculate rates of O2 uptake. CO2 Production. and the respiratory quotient (RO). The effects of temperature and 02 partial pressure on O2 uptake and CO2 production and the RQ were characte∼zed. The steady-state O, partial pressure at which the fruit began to exhibit anaerobic CO2 production (the RQ breakpoint) increased with increasing temperature, which implies that blueberry fruit can be stored at lower O2 partial pressures when stored at lower temperatures.

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Thomas G. Beckman, Ronald L. Perry and James A. Flore

The effects of short-term soil flooding on gas exchange characteristics of containerized sour cherry trees (Prunus cerasus L. cv. Montmorency /P. mahaleb L.) were studied under laboratory conditions. Soil flooding reduced net CO2 assimilation (A) within 24 hours. Net CO2 assimilation and residual conductance to CO2(gr′) declined to ≈30% of control values after 5 days of flooding. Effects on stomatal conductance to CO2 (gS) and intercellular CO2 (Ci) were not significant during the 5 days of treatment. Apparent quantum yield (Φ) gradually declined to 52% that of controls during these 5 days. In a second experiment, CO2 response curves suggested that, initially, stomatal and nonstomatal limitations to A were of about equal importance; however, as flooding continued, nonstomatal limitations became dominant.

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Francesco Di Gioia, Monica Ozores-Hampton, Jason Hong, Nancy Kokalis-Burelle, Joseph Albano, Xin Zhao, Zack Black, Zhifeng Gao, Chris Wilson, John Thomas, Kelly Moore, Marilyn Swisher, Haichao Guo and Erin N. Rosskopf

commercial level, to define and validate a feasible field-scale ASD application procedure. The main factors affecting the level of anaerobiosis and low pH achievable, as well as the microbial type and population growth, and the maintenance of reducing

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Kirk D. Larson, Bruce Schaffer and Frederick S. Davies

One-year-old potted `Peach' mango (Mangifera indica L.) trees were flooded at soil temperatures of 15, 22.5 or 30°C. Hypertrophied lenticels were observed after 5-6 days at 30°C and 6-8 days at 22.5°C, but were not observed after 30 days at 15°C. Cells of hypertrophied lenticels were more spherical and randomly arranged than those of nonhypertrophied lenticels, resulting in increased intercellular airspace. Lenticel hypertrophy also occurred on sterns of trees which were kept moist from intermittant misting, and on excised and intact stem sections. Therefore, formation of hypertrophied lenticels in mango occurs independently of root anaerobiosis and is dependent on floodwater temperature.

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George D. Nanos, Roger J. Romani and Adel A. Kader

The response of pear fruits and suspension-cultured pear fruit cells to 0% or 0.25% O2 is being examined to evaluate the feasibility of using such atmospheres for postharvest insect control. These treatments inhibited ethylene production, had no effect on acetaldehyde content, and increased ethanol production in pears kept at 20C for 10 days. The blossom end area of pear fruits was more prone to anaerobiosis, as indicated by increased alcohol dehydrogenase activity and ethanol content. Pear fruit plugs showed increased respiration and ethylene production rates when skin was present compared to plugs without skin. Methods for measuring activity of alcohol dehydrogenase, pyruvate decarboxylase, and pyruvate kinase have been modified and optimized and will be used to determine changes in pear fruit tissue during low O2 treatment and subsequent recovery in air.

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J.P. Mattheis and D.A. Buchanan

Apple fruit storage lie is prolonged by low-oxygen cold storage, however, ethanol accumulates when oxygen concentration is reduced below the Pasteur point, Upon return to aerobic conditions, dissipation of ethanol occurs due to physical (evaporation) and biochemical processes. Oxidation of ethanol by apple fruit occurs at a slow rate, but ethanol also serves es a substrate for fruit volatile synthesis. This study was conducted to determine changes in concentrations of ethanol and other non-ethylene apple fruit volatiles following periods of anaerobiosis. `Delicious' apples were obtained from a commercial warehouse and stored at 0.05% O2, 0.2% CO2 and 1 C. One day following return to ambient oxygen conditions, several volatiles were identified from anaerobic fruit that were nor produced by the control fruit. All were eaters that contained an ethyl group as the alcohol-derived portion, These included ethyl acetate, ethyl butyrate, ethyl 2-methyl butyrate, ethyl hexanoate and ethyl octanoate. Several esters produced by the controls were not detectable from anaerobic fruit including butyl butyrate, butyl 2-methyl butyrate, propyl hexanoate and 3-methyl butyl hexanoate. After 7 days ripening at 20 C, the amount of ethanol and the additional ethylesters was reduced in anaerobic fruit. Synthesis of esters produced by control fruit but nor by anaerobic fruit during the initial volatile sampling had resumed after 7 days.