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Kara Senger Lewallen and Richard P. Marini

The influence of photosynthetic photon flux (PPF) on peach [Prunus persica (L.) Batsch] fruit quality and the relationship between ground color and flesh firmness was studied by performing three experiments. Fruit with varying ground colors were sampled from different canopy positions with varying PPF. Fruit skin color was measured with a tristimulus colorimeter and values for L* (lightness), chroma (brightness), and hue angle (numerical values for color) were calculated for each fruit. Fruit from the canopy exterior generally were larger, had more surface area colored red, had higher soluble solids concentrations, and were darker, duller, and redder than fruit harvested from interior positions. In all three experiments, the relationship between hue angle and fruit firmness was affected by PPF, but the nature of the relationship (linear vs. curvilinear) and the influence of position was not consistent. When fruit were covered with aluminum foil or a section of the fruit surface was covered with duct tape to prevent light-induced red coloration of the skin, the relationship between hue angle and fruit firmness was similar for different canopy positions. Therefore, the relationship between ground color and fruit firmness is influenced by the light environment in which a fruit develops, and not by canopy position. Ground color does not seem to be a good indicator of fruit firmness because fruit with the same hue angle had greatly differing firmnesses.

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Steven McArtney, Dick Unrath, J.D. Obermiller and Ann Green

total). Treatments were applied to single tree plots arranged in randomized complete block design experiments with four replications. Flesh firmness was measured with a penetrometer fitted with an 11.1-mm tip (Effegi, Alfonsine, Italy) on opposite pared

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Wenjing Guan, Xin Zhao, Donald W. Dickson, Maria L. Mendes and Judy Thies

conventional field, respectively, were used for quality assessment. Three representative marketable fruit from each treatment for each replication were randomly selected. Flesh firmness and SSC were measured twice for each fruit at the middle mesocarp tissue. A

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F.R. Harker and I.C. Hallett

Kiwifruit [Actinidia deliciosa (A. Chev) C.F. Liang et A.R. Ferguson] flesh firmness can decline by as much as 94% during fruit ripening. This phenomenon was investigated at the cellular level, with the aim of characterizing changes in the physiological condition and mechanical properties of cells. The tensile strength of kiwifruit outer pericarp tissue was measured, and low-temperature scanning electron microscopy was used to examine the mode of cell failure at fracture surfaces. The propensity with which cells ruptured was determined by incubating tissue discs in hypertonic and hypotonic solutions, and water potentials, osmotic potentials, turgor pressures, and tissue density were measured. An initial rapid reduction in flesh firmness—from 80 to 27 N during 6 weeks of storage at 0C—was related to a reduction in the adhesion between neighboring cells. Following tensile tests, an examination of fracture surfaces indicated that cells from freshly harvested fruit had ruptured, exposing the cell interior. After 6 weeks of storage, neighboring cells separated from each other without breaking open. With 23 additional weeks of storage at 0C, flesh firmness decreased from 27 to 5 N. The final softening stage was associated with an increase in the proportion of cells that separated at the middle lamella and an increase in the plasticity of the cell wall.

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Laura Puig, Diane M. Varga, Paul M. Chen and Eugene A. Mielke

`Bartlett' pears (Pyrus communis L.) were harvested at commercial maturity (average flesh firmness of 18 lb), stored at 30F for 0, 2, or 4 weeks, and then placed into a ripening room at 68F with or without ethylene to evaluate ripening activities. Pears that were stored in air at 30F for <4 weeks did not ripen after 7 days at 68F in an ethylene-free (no-ethylene) room. These pears ripened normally and uniformly after 7 days at 68F in a room enriched with 100 ppm ethylene (yes-ethylene). `Bartlett' pears that were stored in air at 30F for 4 weeks ripened normally after 5 days at 68F in the yes-ethylene room or 6 days at 68F in the no-ethylene room. The amount of cans produced per ton of fresh processed pears can be maximized most economically by exposing freshly harvested `Bartlett' pears to 100 ppm ethylene at 68F for 7 days before canning.

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Paul M. Chen, Diane M. Varga and Eugene A. Mielke

Abbreviations: EJ, extractable juice; FF, flesh firmness; SSC, soluble solids concentration; TA, titratable acidity. Oregon State Agricultural Experiment Station Technical Paper no. 9834. This study was supported by the Winter Pear Control Committee

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Gorka Perpiñá, Jaime Cebolla-Cornejo, Cristina Esteras, Antonio J. Monforte and Belén Picó

lack AL and external aroma at full maturity. They maintain a higher flesh firmness (FF) and sugar content at maturity before and after harvesting. Therefore, ‘MAK-10’ may be an interesting source of genetic variability to develop new ‘Vedrantais

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Paul M. Chen, Diane M. Varga and Clark F. Seavert

We have established that `d'Anjou' pears (Pyrus communis) are properly ripened for fresh-cut use when flesh firmness (FF) is between 5 lb (2.3 kg) and 7 lb (3.2 kg). In this study, the fruit was ripened in air enriched with 100 ppm (mL·L-1) ethylene at 68 °F (20.0 °C). Afterward, we investigated three slicing methods, each employing a fruit sectionizer for dividing individual pears into eight wedges. The easiest and most convenient cutting procedure involved pouring an antibrowning agent onto the incision, but without allowing the fruit to directly contact the air. We evaluated various combinations of L-ascorbic acid (vitamin C) and potassium chloride (KCl) for their ability to prevent any discoloration while also not affecting taste or injuring the cut surface. The most suitable antibrowning solution contained 10% L-ascorbic acid and 2% KCl (pH 2.3). A dipping time of 30 s was sufficient for maintaining the wedges with little discoloration over a 14-d period, at either 30 or 35 °F (-1.1 or 1.7 °C). Here, we also present a prototype design for a 1.6-pt (0.76-L) transparent plastic container with eight compartments for holding wedges sliced with a commercially available sectionizer.

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Zhenyong Wang and David R. Dilley

AVG, as ReTain™, an inhibitor of ethylene biosynthesis, was used alone or with a subsequent application of ethephon (Ethrel™), an ethylene-releasing chemical, to determine if red color development could be enhanced without over-ripening `Gala' and `Jonagold' apples. Treatments included: 1) AVG alone; 2) AVG followed by ethephon; 3) ethephon alone; and 4) control. Silwet L-77 surfactant was included in all treatments. Application of AVG delayed the onset of the ethylene climacteric and red color development of both cultivars. Application of AVG followed by ethephon similarly delayed the onset of the ethylene climacteric, but red color development at the commercial harvest date was only marginally reduced or not affected. The results were similar in both 1998 and 1999, although environmental stress during the growing seasons differed (1998—heat; 1999—moderate temperatures). The delay of fruit maturation and ripening observed at harvest following AVG +/- ethephon treatments improved storability of fruit in controlled atmosphere (CA) storage, as demonstrated by low internal ethylene levels after storage, and high retention of flesh firmness and shelf-life, while control fruit and those treated only with ethephon entered the ethylene climacteric during storage, and flesh firmness subsequently declined during shelf-life evaluation. Chemical name used: aminoethoxyvinylglycine (AVG).

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Gregory M. Peck, Preston K. Andrews, John P. Reganold and John K. Fellman

Located on a 20-ha commercial apple (Malus domestica Borkh.) orchard in the Yakima Valley, Washington, a 1.7-ha study area was planted with apple trees in 1994 in a randomized complete block design with four replications of three treatments: organic (ORG), conventional (CON), and integrated (INT). Soil classification, rootstock, cultivar, plant age, and all other conditions except management were the same on all plots. In years 9 (2002) and 10 (2003) of this study, we compared the orchard productivity and fruit quality of `Galaxy Gala' apples. Measurements of crop yield, yield efficiency, crop load, average fruit weight, tree growth, color grades, and weight distributions of marketable fruit, percentages of unmarketable fruit, classifications of unmarketable fruit, as well as leaf, fruit, and soil mineral concentrations, were used to evaluate orchard productivity. Apple fruit quality was assessed at harvest and after refrigerated (0 to 1 °C) storage for three months in regular atmosphere (ambient oxygen levels) and for three and six months in controlled atmosphere (1.5% to 2% oxygen). Fruit internal ethylene concentrations and evolution, fruit respiration, flesh firmness, soluble solids concentration (SSC), titratable acidity (TA), purgeable volatile production, sensory panels, and total antioxidant activity (TAA) were used to evaluate fruit quality. ORG crop yields were two-thirds of the CON and about half of the INT yields in 2002, but about one-third greater than either system in 2003. High ORG yields in 2003 resulted in smaller ORG fruit. Inconsistent ORG yields were probably the result of several factors, including unsatisfactory crop load management, higher pest and weed pressures, lower leaf and fruit tissue nitrogen, and deficient leaf tissue zinc concentrations. Despite production difficulties, ORG apples had 6 to 10 N higher flesh firmness than CON, and 4 to 7 N higher than INT apples, for similar-sized fruit. Consumer panels tended to rate ORG and INT apples to have equal or better overall acceptability, firmness, and texture than CON apples. Neither laboratory measurements nor sensory evaluations detected differences in SSC, TA, or the SSC to TA ratio. Consumers were unable to discern the higher concentrations of flavor volatiles found in CON apples. For a 200 g fruit, ORG apples contained 10% to 15% more TAA than CON apples and 8% to 25% more TAA than INT apples. Across most parameters measured in this study, the CON and INT farm management systems were more similar to each other than either was to the ORG system. The production challenges associated with low-input organic apple farming systems are discussed. Despite limited technologies and products for organic apple production, the ORG apples in our study showed improvements in some fruit quality attributes that could aid their marketability.