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  • Author or Editor: William S. Conway x
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The effects of organosilicone and more conventional hydrocarbon surfactants on postharvest radiolabeled calcium (Ca) and on Ca solution infiltration into `Golden Delicious' apples were examined to provide a direct and more efficient pressure infiltration technique to increase fruit Ca concentration. Both radiolabeled Ca infiltration and the proportional increase in fruit Ca estimated by fruit weight gain from Ca solutions of known concentration were significantly enhanced by a range of surfactants having differing chemical structures. Two organosilicone surfactants, Silwet L-77 and Silwet L-7604, known for their greater capacity to lower the surface tension of solutions than conventional hydrocarbon surfactants, were the best among the surfactants tested at augmenting Ca infiltration. Applications of surfactants to fruit were as effective or more effective when used as a pretreatment rather than by mixing with Ca solutions. The applied atmospheric pressure necessary to infiltrate Ca to levels considered sufficient to maintain fruit firmness and resist decay during storage could be lowered in fruit treated with organosilicone surfactants. Postharvest surfactant and Ca treatments may offer a practical means of increasing the Ca concentration of apple fruit.

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`Golden Delicious' and `Red Rome' apples were pressure infiltrated (69 kPa for 2 or 4 min) at harvest with 0, 1, 2, 3 or 4%, and 0, 2, 4, 6 or 8% CaCl2 solutions (w/v), respectively, and placed in 0°C storage. Juice was extracted from the apples after 0, 2, 4 or 6 months in storage. Sensory evaluation of the juice was conducted to determine if CaCl2 concentration affected color, off-flavors, suspended particles or overall acceptability of the juice. Juice color was judged lighter with increased CaCl2 in both cultivars. Detection of off-flavors decreased as CaCl2 was increased in juice from `Red Rome'; whereas, off-flavors increased as CaCl2 was increased in `Golden Delicious' juice. CaCl2 treatments decreased suspended particles in both cultivars. As CaCl2 was increased overall acceptability of juice from `Red Rome' increased, while acceptability of juice from `Golden Delicious' decreased.

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`Golden Delicious' and `Red Rome' apples were pressure infiltrated (69 kPa for 2 or 4 min) at harvest with 0, 1, 2, 3 or 4%, and 0, 2, 4, 6 or 8% CaCl2 solutions (w/v), respectively, and placed in 0°C storage. Juice was extracted from the apples after 0, 2, 4 or 6 months in storage. Sensory evaluation of the juice was conducted to determine if CaCl2 concentration affected color, off-flavors, suspended particles or overall acceptability of the juice. Juice color was judged lighter with increased CaCl2 in both cultivars. Detection of off-flavors decreased as CaCl2 was increased in juice from `Red Rome'; whereas, off-flavors increased as CaCl2 was increased in `Golden Delicious' juice. CaCl2 treatments decreased suspended particles in both cultivars. As CaCl2 was increased overall acceptability of juice from `Red Rome' increased, while acceptability of juice from `Golden Delicious' decreased.

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`Golden Delicious' (`GD') and `Red Rome' (`RR') apples were pressure infiltrated at harvest with 0, 1, 2, 3 or 4% and 0, 2, 4, 6 or 8% CaCl2 solutions (w/v), respectively. Sauce was prepared after 0, 2, 4 and 6 months in 0°C storage. Sensory evaluation was conducted to determine the effects of CaCl2 concentration on color, off-flavors, consistency, uniformity of particles, and overall acceptability of the sauce. Sauce from `RR' was lighter while sauce from `GD' was darker with increased CaCl2. Calcium chloride increased the consistency of `RR' and `GD' sauce but the highest concentrations decreased the consistency of `GD' sauce. The uniformity of sauce particles from both cultivars decreased with increased CaCl2. The presence of off-flavors increased in `GD' sauce with the highest concentrations but decreased in `RR' sauce as CaCl2 was increased. Overall acceptability of sauce made from `RR' and `GD' increased as CaCl2 increased, however, acceptability of sauce made from `GD' decreased at the highest concentrations of CaCl2.

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Blue mold of apples, incited by Penicillium expansum, causes extensive losses on stored apples worldwide. Despite the severity of this problem, apple breeders do not evaluate their crosses for resistance to this disease, because there has been little resistance to blue mold in the gene pool of the germplasm used. A new apple germplasm collection from the center of origin in Kazakhstan, maintained in Geneva, NY, and representing a much broader gene pool, was evaluated for resistance to blue mold. Apples were harvested from the Elite collection trees that were clonally propagated from budwood collected in Kazakhstan and from seedling trees originating from seeds of the same trees as the Elite budwood or from other wild seedling trees in Kazakhstan. Fruit from 83 such accessions were harvested at the preclimacteric to climacteric stage, wound-inoculated with P. expansum at 103, 104, and 105 mL−1 conidial suspension, incubated for 5 d at 24 °C, and evaluated for decay incidence and severity. Two accessions were classified as immune (no decay at 103 and 104 mL−1), four as resistant (no decay at 103 mL−1), 53 as moderately resistant (lesions less than 10 mm at 103 mL−1), and 24 as susceptible. There were positive correlations (r = 0.92, 0.86, and 0.91) between decay severity and all three inoculum levels. Our results indicate a greater genetic diversity among the Kazak apple collection than among cultivated apples as evidenced by their broad range of fruit maturity, quality, and disease resistance patterns. The immune and resistant accessions may serve as a source of resistance in breeding programs and can be useful in explaining the mechanism of resistance to blue mold in apples.

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`Golden Delicious' apples (Malus domestics Borkh.) were treated with heat or CaCl2 solutions or a combination thereof to determine the effects of these treatments on decay and quality of fruit in storage. Heat treatment at 38C for 4 days, pressure infiltration with 2% or 4% solutions of CaCl2, or a combination of both, with heat following CaCl2 treatment affected decay and firmness during 6 months of storage at 0C. The heat treatment alone reduced decay caused by Botrytis cinerea (Pers.:Fr.) by ≈30%, while heat in combination with a 2% CaC12 solution reduced decay by ≈60 %. Calcium chloride solutions of 2% or 4% alone reduced decay by 40 % and 60 %, respectively. Heat treatments, either alone or in combination with CaC12 treatments, maintained firmness (80 N) best, followed by fruit infiltrated with 2% or 4% solutions of CaCl2 alone (70 N) and the nontreated controls (66 N). Instron Magness-Taylor and Instron compression test curves show that heat-treated fruit differed qualitatively and quantitatively from nonheated fruit. Heat treatment did not increase the amount of infiltrated Ca bound to the cell wall significantly, and a combination of heat treatment after CaCl2 infiltration increased surface injury over those fruit heated or infiltrated with CaCl2 solutions alone.

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Fruit quality, sensory characteristics, and volatiles produced by 'Gala' apples (Malus ×domestica Borkh.) were characterized following regular atmosphere (RA) storage without and with a prestorage heat treatment (38 °C for 4 days) or controlled atmosphere (CA) storage at 0 and 2 °C for 0 to 6 months plus 7-day shelf life at 20 °C. Static CA conditions were 0.7 kPa O2 plus 1.0 kPa CO2, 1.0 kPa O2 plus 1.0 kPa CO2, and 1.5 kPa O2 plus 2.5 kPa CO2. Most of the more abundant volatiles were esters; the rest were alcohols, an aldehyde, a ketone, and an aryl ether. Respiration and ethylene production rates, internal atmospheres of CO2 and ethylene, and volatile levels were reduced following CA storage compared with RA storage without and with a prestorage heat treatment. Magness-Taylor and compression firmness, titratable acidity, and sensory scores for firmness, sourness, apple-fruity flavor, and overall acceptability were higher for CA-than for RA-stored fruit. Soluble solids content and sensory scores for sweetness were similar among all treatments. Quality and sensory characteristics were generally similar in heated and nonheated RA-stored fruit, and between 0 and 2 °C in CA- and RA-stored fruit. While one CA regime had a higher CO2 concentration than the others tested, CA effects on quality and sensory characteristics were generally more pronounced at the lower O2 levels. Quality characteristics declined between 2 and 4 months storage. The results indicate that short-term CA storage can maintain instrumental and sensory quality of 'Gala' apples.

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Prestorage heat, CA storage, and pre- and poststorage treatments with the ethylene action inhibitor, 1-methylcyclopropene (MCP), were tested for their efficacy at inhibiting fungal decay and maintaining quality in `Golden Delicious' apples [Malus sylvestris (L.) Mill. Yellow Delicious Group] stored 0 to 5 months at 0 °C and 7 days at 20 °C. Before storage in air at 0 °C, preclimacteric fruit were treated with either MCP at a concentration of 1 μL·L-1 for 17 hours at 20 °C, 38 °C air for 4 days, MCP plus heat, or left untreated. Some sets of untreated fruit were stored in a controlled atmosphere of 1.5 kPa O2 and 2.5 kPa CO2 at 0 °C while other sets were removed from cold storage in air after 2.5 or 5 months, warmed to 20 °C, and treated with 1 μL·L-1 MCP for 17 hours. Prestorage MCP, heat, MCP plus heat treatments and CA storage decreased decay severity caused by wound-inoculated Penicillium expansum Link, Botrytis cinerea Pers.:Fr., and Colletotrichum acutatum Simmonds (teleomorph Glomerella acutata J.C. Guerber & J.C. Correll sp.nov.). Poststorage MCP treatment had no effect on decay severity. Both prestorage MCP treatment and CA storage delayed ripening as indicated by better retention of green peel color, titratable acidity, and Magness-Taylor flesh firmness, and the reduced respiration, ethylene production rates, and volatile levels that were observed upon transferring the fruit to 20 °C. The prestorage MCP treatment delayed ripening more than CA storage. Following 5 months cold storage, the prestorage MCP treatment maintained the shape of the compression force/deformation curve compared with that of fruit at harvest, as did CA storage, but at a lower force profile. The heat treatment had mixed effects on ripening: it hastened loss of green peel color and titratable acidity, but maintained firmness and delayed increases in respiration, ethylene production and volatile levels following cold storage. The MCP plus heat treatment inhibited ripening more than heat treatment alone but less than MCP treatment alone. In one of 2 years, the MCP plus heat treatment resulted in superficial injury to some of the fruit. Results indicated that MCP may provide an effective alternative to CA for reducing decay severity and maintaining quality during postharvest storage of `Golden Delicious' apples. Prestorage heat to control decay and maintain quality of apples needs further study, especially if used in combination with MCP.

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The effects of 36 organosilicone and conventional carbon-based surfactants on postharvest infiltration of radiolabeled and unlabeled Ca solutions into `Golden Delicious' apples (Malus domestica Borkh) were examined to devise a more efficient pressure infiltration technique to increase fruit Ca concentration. Radiolabeled Ca infiltration and the proportional increase in fruit Ca estimated by fruit weight gain from Ca solutions of known concentration were significantly enhanced by a range of surfactants having different chemical structures. Tween 60 and 80; Triton X-45, X-100, X-114, X-305, and X-405; and Silwet L-77 and L-7604 enhanced Ca infiltration. The two organosilicone surfactants, Silwet L-77 and Silwet L-7604, known for their greater capacity to lower the surface tension of solutions than conventional carbon-based surfactants, were the most effective at augmenting Ca infiltration. Applications of surfactants to fruit were as or more effective when used as a pretreatment rather than mixing the surfactant with the Ca solutions. The pressure necessary to increase Ca to levels considered sufficient to maintain fruit firmness and resist decay during storage could be lowered in fruit treated with organosilicone surfactants. Sequential postharvest surfactant and Ca treatments may be a practical means of increasing the Ca concentration in apples.

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`Golden Delicious' apples (Malus domestica Borkh.) were treated after harvest with heat (air at 38 °C for 4 days or 42 °C for 1 day) or 2% CaCl2 (w/v; applied as a dip or pressure-infiltrated) or a combination of the two and stored at 0 °C for ≤6 months. Decay caused by Botrytis cinerea Pers.:Fr. after inoculation to a depth of 2 mm with a conidial suspension virtually was eliminated in stored fruit heated at 38 °C, regardless of Ca treatment. Apples punctured to a depth of 0.5 mm (but not 2 mm) and inoculated with B. cinerea on removal from storage were almost completely protected from poststorage decay if they had previously been pressure-infiltrated with 2% CaCl2, regardless of the heat regime. Heating fruit at 42 °C and dipping in 2% CaCl2 were only partially effective in preventing decay from either pre- or poststorage inoculations. Fruit firmness was not related to resistance to decay.

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