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Neil L. Heckman, Garald L. Horst, Roch E. Gaussoin, and Kevin W. Frank

Internal heating during sod storage can lead to plant deterioration and is a limiting factor in sod transportation. Storage practices such as the use of refrigeration and vacuum packaging have increased storage time; however, these are usually not practical or economical. Experiments were conducted to develop a feasible growth regulator management technique, using trinexapac-ethyl, to increase the storage life of Kentucky bluegrass (Poa pratensis L.) sod. Experimental setup for all experiments was a completely randomized design with a 2 (trinexapac-ethyl vs. control) × 3 (storage times) factorial treatment arrangement with 3 replications. Trinexapac-ethyl was applied at 0.23 kg·ha-1 to Kentucky bluegrass 2 weeks prior to harvesting. Results showed that sod treated with trinexapac-ethyl was as much as 10 °C cooler than the controls in the center of the sod stacks after 48 hours of storage. The reduced sod temperatures led to a 30% greater tensile strength and 17% better quality ratings in treated sod after 24 hours of storage. A preharvest application of trinexapac-ethyl appears to increase storage times of Kentucky bluegrass sod, which may improve sod market quality. Chemical name used: [4(cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] (trinexapac-ethyl).

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Deirdre M. Holcroft, Maria I. Gil, and Adel A. Kader

The influence of CO2 on color and anthocyanin concentration in the arils of `Wonderful' pomegranate (Punica granatum L.) was investigated. Pomegranates were placed in jars ventilated continuously with air or air enriched with 10% or 20% CO2 at 10°C for 6 weeks. Samples were taken initially, and after 1, 2, 4, and 6 weeks and anthocyanin concentration was measured by HPLC. The arils of the pomegranates stored in air were deeper red than those stored in CO2-enriched atmospheres. This increase in red color resulted from an increase in anthocyanin concentration. Arils from fruit stored in air+10% CO2 had a lower anthocyanin concentration than air-stored fruit, and atmospheres enriched with 20% CO2 suppressed anthocyanin biosynthesis. Anthocyanin concentration was well-correlated to the activity of phenylalanine ammonia lyase (PAL), but not to glucosyltransferase (GT) activity. Moderate CO2 atmospheres (10%) prolong the storage life and maintain the quality of pomegranates, including an adequate red color of the arils.

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Kathleen M. Griffiths, Mohammad H. Behboudian, and Melanie Dingle

Asian pear (Pyrus serotina Rehder) is endemic to southern China, Korea and Japan where it is an important fruit. Recent introduction into New Zealand has necessitated research to achieve high fruit quality. In this experiment three irrigation treatments were imposed on the cultivar Nijisseiki and the effect on fruit quality and storage life assessed. They were: a control for which soil water was maintained at 85% of field capacity (FC), “field” receiving only rainfall, and regulated deficit irrigation (RDI) in which soil water was depleted to 50% FC until rapid fruit growth started and then treated as in the control. Fruit weight and firmness were higher in the control and soluble solids were higher in the field treatment whose fruit matured earlier. Irrigation treatment showed no effect on the ripening pattern of the fruit in coolstorage or the incidence of the postharvest disorder flesh spot decay. Nitrogen and potassium levels were highest in the control fruit. However, levels of Mg, Ca, and P were not affected by irrigation.

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Jun Song, Lihua Fan, Charles F. Forney, and Michael A. Jordan

Volatile emissions and chlorophyll fluorescence were investigated as potential signals of heat injury for apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] fruit. `McIntosh', `Cortland', `Jonagold', and `Northern Spy' apples were exposed to 46 °C for 0, 4, 8, or 12 hours (heat treatments). Following treatments, fruit were kept at 20 °C and evaluated after 1, 2, 4, or 7 days. Heat treatments induced volatile production including ethanol and ethyl acetate. The 8 and 12 hours heat treatments increased ethanol and ethyl acetate production in all four cultivars by as much as 170- and 11-fold, respectively, 1 day after treatments. Heat treatments also reduced ethylene production and chlorophyll fluorescence. Heat for 12 hours caused serious flesh browning. Among the cultivars investigated, `Northern Spy' and `McIntosh' were most susceptible to heat stress based on the degree of flesh browning. Correlation coefficients of heat stress induced ethanol emission and chlorophyll fluorescence with flesh browning were 0.82 and -0.66, respectively. The nondestructive measurements of ethanol emission and chlorophyll fluorescence have potential to identify stressed fruit with reduced quality or compromised storage life.

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Gene E. Lester and Michael A. Grusak

Muskmelon senescence is directly associated with a decline in hypodermal mesocarp membrane integrity and its Ca concentration, but infusing Ca into melons has been a problem. Fully ripened and abscised hybrid honeydew [Cucumis melo L. (Inodorus Group) `Honey Brew'] and netted muskmelon [Cucumis melo L. (Reticulatus Group) `Explorer'] fruit were submerged (dipped) 20 min at 25 ± 3 °C in a solution containing a Ca-chelate, a Mg-chelate, a combination of both chelates, or no mineral chelate. Following 10 or 24 days of cold storage (4 °C for `Explorer' and 10 C for `Honey Brew'), fruit were analyzed for mineral content and various senescence-related parameters. Abscised `Honey Brew' fruit dipped in either Ca-chelate or (Ca+Mg)-chelate and abscised `Explorer' fruit dipped in (Ca+Mg)-chelate, followed by 10 days cold storage, had hypodermal mesocarp Ca concentrations of at least 6.0 mg·g-1 dry weight. Maintaining hypodermal mesocarp tissue Ca concentrations at this level during postharvest storage, especially for fully ripe `Honey Brew' fruit, maintained membrane integrity and fruit firmness, and extended storage life 2.4-fold (i.e., to 24 days). The senescence regulatory effect of postharvest Ca-chelate treatments on abscised `Explorer' was highly variable, compared to `Honey Brew', which appeared to be due to the surface netting interfering with movement of Ca into the hypodermal mesocarp. Thus, postharvest Ca-chelate application to abscised `Honey Brew' fruit could delay fruit senescence in commercial storage, and open up new markets for fully ripened honeydew melons.

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Gene Lester and Eduardo Stein

Changes in the physical and chemical properties of the plasma membrane from hypodermal mesocarp tissue of netted muskmelon (Cucumis melo L. var. reticulatus Naud.) fruit were compared in relation to the permeability changes of the same tissue during fruit maturation and storage at 4 or 24C. As muskmelon fruit progress from immaturity to maturity, and with storage of mature fruit at 4 or 24C, increased permeability of the hypodermal-mesocarp tissue occurs coincident with an increase in the saturation index of the plasma membrane phospholipids. Buoyant density of the plasma membrane from hypodermal mesocarp tissue increased from 1.13 to 1.14 g·cm-3 during fruit maturation. Vanadate-sensitive ATPase (EC 3.6.1.35) activity was highest in mature fruit at harvest. After 10 days of storage, vanadate-sensitive ATPase activity was much lower in fruit kept at 24C than in those kept at 4C. The decrease in vanadate-sensitive ATPase activity in fruit stored at 24C was correlated with increased hypodermal-mesocarp membrane permeability. We suggest that biochemical changes affecting the lipid matrix of the plasma membrane influence fruit membrane permeability and possibly muskmelon storage life.

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I. Tayfun Agar, William V. Biasi, and Elizabeth J. Mitcham

Ripening behavior of `Bartlett' pears (Pyrus communis L.), with or without ethylene (C2H4) treatment, was assessed at harvest, and after 2, 4, 6 and 12 weeks of cold storage at –1 °C. Fruit exhibited increasing rates of C2H4 production and consequently faster ripening rates with increased length of cold storage. Ripening characteristics were influenced by storage duration, but to different degrees. The data indicate that the threshold C2H4 concentration for softening may be lower than that for color change from green to yellow. Ethylene treatment for 24 h at harvest resulted in a rate of ripening equivalent to that following cold storage for 2 to 4 weeks, depending on the orchard location. Storage for 12 weeks significantly increased C2H4 production upon transfer to ambient temperature, indicating that fruit were reaching the end of their storage life. `Bartlett' pears may ripen to a firmness of 14 N (ready to eat) at 20 °C within 2.5 to 7 days depending upon the duration of prior cold storage.

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Noida A. Biglete, Robert F. Testin, and James W. Rushing

A triploid watermelon cultivar, `Crimson Trio' and a seeded cultivar, `Mirage', were shrink-wrapped in four different films: Cryovac D940, Cryovac D955, and Magellan film with and without a blended biocide. Unwrapped fruits served as the control. Fruits were stored at either 1.5, 10 and 21°C for three weeks plus an additional week at 21°C to simulate retail marketing. Total soluble solids (TSS) and pulp color measurements were taken after harvest and at the end of the storage period while weight, disease incidence, chilling injury and visual quality rating were monitored at weekly intervals. Results showed that the seedless variety have better postharvest qualities in terms of storage life, TSS and chilling resistance than the seeded variety. Wrapped fruits had less weight loss, higher TSS and better rind color than the unwrapped fruits at the end of the storage period. However, all wrapping treatments, including the biocidal film increased disease incidence compared to unwrapped controls. Also, wrapping did not alleviate chilling injury, which was most severe in fruits stored at 1.5°C and then held at 21°C for one week.

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Charles F. Forney

Volatile compounds make a significant contribution to the quality and storage life of fresh strawberries, blueberries, and raspberries. Strawberry aroma is composed predominately of esters, although alcohols, ketones, and aldehydes are also present in smaller quantities. The major volatiles contributing to aroma include ethyl butanoate, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, ethyl hexanoate, methyl butanoate, linalool, and methyl hexanoate. In lowbush (wild) blueberries, aroma is predominated by esters and alcohols including ethyl and methyl methylbutanoates, methyl butanoate, 2-ethyl-1-hexanol, and 3-buteneol, while highbush blueberry aroma is dominated by aromatic compounds, esters, terpenes and long chain alcohols. The aroma of raspberries is composed of a mixture of ketones and terpenes, including damascenone, ionone, geraniol, and linalool. The composition and concentration of these aroma compounds are affected by fruit maturity and storage conditions. As fruit ripen, the concentration of aroma volatiles rapidly increases. This increase in volatile synthesis closely follows pigment formation both on and off the plant. In strawberry fruit, volatile concentration increases about 4-fold in the 24-h period required for fruit to ripen from 50% red to fully red on the plant. In storage, volatile composition is affected by storage temperature, duration, and atmosphere. Postharvest holding temperature and concentrations of O2 and CO2 can alter the quantity and composition of aroma volatiles. The effects of postharvest environments on volatile composition will be discussed.

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Graeme A. King and Stephen C. Morris

The postharvest senescence of broccoli (Brassica oleracea L. Italica group) was studied immediately after harvest until senescence was essentially completed at 20C. Changes in respiration, ethylene production, and color were determined for florets, branchlets, and heads of three cultivars of field-harvested `Green Beauty', `Dominator', and `Shogun' broccoli. Changes in respiration and ethylene production were also determined for 3 hours of preharvest and 24 hours of postharvest storage using broccoli grown in containers. Carbon dioxide produced from heads of container-grown broccoli and from heads, branchlets, and florets of field-harvested broccoli decreased markedly during the first 12 hours of postharvest storage before stabilizing. The respiratory quotient shifted toward a more oxidative metabolism in parallel with the respiratory decline. Ethylene production during storage showed no consistent relationship to yellowing. However, time until onset of yellowing was broadly related to the basal levels of ethylene production. The maximum storage life at 20C is ≈72 hours. Branchlets are useful model systems for investigating broccoli senescence.