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Stephen R. Drake, Fenton E. Larsen, and S.S. Higgins

Influences of rootstock on the quality of `Granny Smith' and `Greenspur' apples (Malus domestica Borkh.) were evaluated over an extended harvest period and after cold storage. Apples from trees on M.26 rootstock had the higher firmness, soluble solids concentration (SSC), and Ca content, but poorer external color (red blush) and a higher percentage of solar injury than fruit from trees on seedling or MM.111 rootstock. External greenness was best on apples from MM.111 rootstock. `Granny Smith' apples had higher firmness, soluble solids, acids, and carbohydrate contents, and less scald but poorer external greenness than `Green spur' apples. `Granny Smith' or `Greenspur' apples from M.26 rootstock appeared to mature earlier than those on MM.111.

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S.R. Drake, T.A. Eisele, M.A. Drake, D.C. Elfving, S.L. Drake, and D.B. Visser

This study was conducted over three crop seasons using 'Delicious' (Scarletspur strain) apple trees on MM.111 rootstock. The bioregulators aminoethoxyvinylglycine (AVG) and ethephon (ETH) were applied alone or in combinations at various time intervals before harvest. Fruit response to bioregulators was evaluated at harvest and after storage. AVG applied 4 weeks before first harvest retarded starch loss at harvest, retained greater firmness, and reduced internal ethylene concentration and watercore of fruit at harvest and after both regular and controlled atmosphere storage. AVG did not influence peel color (hue values), but the flesh color of treated apples was more green. AVG in all instances tended to reduce the sensory scores for apples and apple juice. In contrast, ETH enhanced starch hydrolysis, flesh color development (green to more yellow), and soluble solids concentration while reducing titratable acidity levels. ETH had no influence on fruit firmness at harvest, but reduced firmness levels after storage in an inverse relationship to the concentration applied. Sensory values for whole apples were not influenced by ETH treatment, but ETH improved sensory preference for apple juice, particularly at early harvest. Applying AVG before ETH enhanced soluble solids and sensory scores for both fruit and juice. Treating with AVG followed by ETH at 150 mg·L–1 permitted the maintenance of satisfactory firmness values (>53.4 N) after long-term storage along with better quality and sensory perceptions. Using specific combinations of both AVG and ETH permitted ETH-mediated improvements in objective and perceived fruit quality to be obtained without the losses in flesh firmness and storability due to uncontrolled ethylene evolution and ripening typically observed when ETH is applied alone preharvest.

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S.R. Drake, T.A. Eisele, D.C. Elfving, M.A. Drake, S.L. Drake, and D.B. Visser

In a study conducted over three crop seasons, Ethrel (ETH) increased the Brix, sucrose, and sorbitol content of 'Scarletspur Delicious' apple juice while reducing the fructose content. Both longer preharvest exposure to, and higher concentrations of, ETH had a stronger influence than application closer to harvest and/or at lesser amounts. Time of ETH application tended to influence individual carbohydrates more so than amount of ETH applied. ETH reduced total acidity and also reduced apple juice individual acid (quinic and malic) contents with longer preharvest exposure or higher concentrations. Aminoethoxyvinylglycine [AVG (ReTain)] reduced both Brix and sucrose content of 'Scarletspur Delicious' apple juice, but had no influence on either total acidity or individual acid contents. Combinations of AVG with ETH tended to counteract the influence of either used alone on total Brix, carbohydrates, total acidity and individual acids. Mineral content of 'Scarletspur Delicious' apple juice was not strongly influenced by application of either ETH or AVG.

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S.R. Drake, D.C. Elfving, M.A. Drake, T.A. Eisele, S.L. Drake, and D.B. Visser

This study was conducted over two crop seasons using `Scarletspur Delicious' and `Gale Gala' apple trees (Malus ×domestica). The bioregulators aminoethoxyvinylglycine (AVG), ethephon (ETH), and 1-methylcyclopropene (MCP) were applied at various times before or after harvest. Fruit response was evaluated at harvest and after regular atmosphere (RA) and controlled atmosphere (CA) storage [2.0% oxygen (O2) and <2.0% carbon dioxide (CO2) at 0 °C] and quality of whole and juice apple products evaluated. AVG reduced starch loss and ethylene production, enhanced firmness, and reduced cracking in `Gale Gala,' but reduced sensory acceptance of apples and apple juice. ETH intensified starch loss, ethylene production, and reduced firmness, but did not affect `Gale Gala' fruit cracking. AVG followed by ETH reduced starch loss, ethylene production, and cracking and maintained firmness. This combination also aided in sensory acceptance of apples but reduced sensory preference of apple juice. Exposure to postharvest MCP improved flesh firmness retention and reduced ethylene production after both RA and CA storage. MCP either favored or reduced sensory acceptance of whole apples, depending on the particular season, but reduced sensory preference of apple juice. Sensory scores for `Scarletspur Delicious' apples were more strongly modified by bioregulators than were `Gale Gala' apples.

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S.R. Drake, D.C. Elfving, and R.D. Gix

Pears (Pyrus communis `d'Anjou') were packed in six commercial paper wraps (dry; 3% oil; 3% oil with copper and ethoxyquin; 6% oil; 6% oil with ethoxyquin; 9% oil). After packing, the pears were placed in three different controlled atmosphere (CA) storage conditions in commercial CA rooms: 1) 1.5% oxygen (O) and 1% carbon dioxide (CO2); 2) 1.5% O2 and 3% CO2; 3) 1.5% O2 and 1% CO2 for 60 days, 4% O2 for 60 more days and finally 6% O2 for an additional 90 days. Pears were stored in CA for 120 and 210 days, with or without an additional 30 days in regular atmosphere (RA) storage to simulate shipping and handling. Objective quality evaluations were conducted after each storage period and sensory evaluations after 210 days of storage. Paper type influenced both the peel and flesh color of pears before and after ripening, but did not influence firmness, soluble solids or acid content. Subjective ratings of appearance and disorder incidence were unacceptable for pears stored in a variable atmosphere wrapped in dry or paper containing 3% oil. The disorder black speck was present only in pears wrapped in paper with 6% oil and stored in an atmosphere of 1.5% O2 and 1% CO2. Pears stored in an atmosphere of 1.5% O2 and 3% CO2 received acceptable subjective scores regardless of paper type.

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S.R. Drake, T.A. Eisle, and H. Waelti

`Delicious' apples were held in controlled atmosphere (CA) storage at various carbon dioxide (CO2) levels for 9 months. CO2 levels were either 1, 3, or 5% with an additional treatment that was increased by 1% every 6 weeks to a maximum of 5%. For each treatment oxygen was 1%, and storage temperature was 1°C. Little quality difference was noted for the `Delicious' apples immediately after storage or after an 8 day ripening period. Firmness, external or internal color, titratable acidity and amount of scald showed no difference among the different storage treatments. Total carbohydrates and fructose were higher in apples stored at CO2 levels above 1 %. Sensory panelists found no flavor difference in `Delicious' apples regardless of CO2 storage level atmospheres. If one considers the substantial cost savings that are possible with increased CO2 in the storage system, there is good reason to increase the CO2 storage level in long term storage.

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K.C. Shellie, L.G. Neven, and S.R. Drake

Sweet cherries (Prunus avium `Bing') exposed to 113 or 117 °F (45 or 47 °C) in an atmosphere of 1% oxygen with 15% carbon dioxide (balance nitrogen) were heated to a maximum center temperature of 112 or 115 °F (44 or 46 °C) in 41 or 27 min, respectively. Heated cherries had similar incidence of pitting and decay, and similar preference ratings after 14 days of storage at 34 °F (1 °C) as nonheated or methyl bromide fumigated fruit. Heated cherries and methyl bromide fumigated cherries were less firm after 14 days of cold storage than nonheated, control fruit. The stems of methyl bromide fumigated cherries were less green than heated or nonheated cherries. Cherries exposed to 113 °F had lower titratable acidity than nonheated cherries, fumigated cherries, or cherries exposed to 117 °F. Cherry quality after 14 days of cold storage was not affected by hydrocooling before heating (5 min in water at 34 °F) or by method of cooling after heating (hydrocooling, forced air cooling, or static air cooling). Cherries stored for 14 days at 34 °F in 6% oxygen with 17% carbon dioxide (balance nitrogen) had similar market quality as cherries stored in air at 34 °F. Results suggest that `Bing' sweet cherry can tolerate heating in an atmosphere of low oxygen containing elevated carbon dioxide at doses that may provide quarantine security against codling moth (Cydia pomonella) and western cherry fruit fly (Rhagoletis cingulata).

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S.R. Drake, E.A. Mielke, and D.C. Elfving

`Concorde' pears from three plantings were harvested at various maturities, stored in regular (RA) or controlled atmosphere (CA) storage and their quality evaluated. Starting at a firmness of 57.0 N (12.81 lbf), `Concorde' pears can be harvested over a period of 14 days with no loss in quality and be good candidates for either RA or CA storage. A 14-day delay in harvest resulted in a one box size increase. Regardless of the time of harvest, `Concorde' pears can be stored in RA for periods not to exceed 90 days. RA storage beyond 90 days resulted in reduced appearance, poor pedicel condition, and enhanced internal breakdown. Early harvest should be considered when RA storage is expected to exceed 90 days; however astringency may develop. Regardless of harvest, `Concorde' pears can be stored for 180 days in CA with no quality loss, particularly if the CA composition is 1.5% oxygen (O2) and 1.0% carbon dioxide (CO2). Internal breakdown can be a problem in CA if the CO2 exceeds 1.0%. Low O2 (<1.5%) CA is not recommended for `Concorde' pears.

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S.R. Drake, D.C. Elfving, and T.A. Eisele

Quality of `Cripps Pink' apples (Malu × domestica) harvested at a starch index of 2 and 4 was evaluated over three crop seasons. Apple quality was evaluated after harvest and after regular atmosphere (RA) and controlled-atmosphere (CA) storage at 1% O2 and 1% CO2, 1% O2 and 3% CO2, and 1% O2 and 5% CO2 (1 year only) at 1 ºC (33 to 34 ºF). Over three seasons, commercially acceptable fruit quality was achieved on either harvest date following both long-term RA and CA storage. Fruit size was not different between apples harvested at a starch index of 2 or 4. Firmness and acids remained at acceptable levels [62 N (14 lb) and ≥0.50%, respectively] in `Cripps Pink' apples regardless of maturity, storage time or storage conditions. Delaying harvest after a starch index of 2 was achieved increased soluble solids concentration (SSC), SSC to TA (titratable acidity) ratio, peel color, malic acid and citric acid concentrations but decreased fructose content. `Cripps Pink' apples responded well to CA storage conditions of 1% O2 with 1% or 3% CO2, but displayed significant firmness loss and greatly increased internal breakdown at 1% O2 and 5% CO2 at 1 ºC.

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J.D. Hansen, M.L. Heidt, M.A. Watkins, S.R. Drake, J. Tang, and S. Wang

Quarantine regulations require domestic sweet cherries (Prunus avium) exported to Japan to be treated to control codling moth [Cydia pomonella (Lepidoptera: Tortricidae)]. The current procedure, methyl bromide fumigation, may be discontinued because of health, safety, and environmental concerns. To examine a potential alternative method, `Bing' sweet cherries were each infested with a codling moth larva, submerged in a 38 °C water bath for 6 minutes pretreatment, then exposed to various temperatures generated by radio frequency and held at that temperature for different times: 50 °C for 6 minutes, 51.6 °C for 4 minutes, 53.3 °C for 0.5 minutes, and 54.4 °C for 0.5 minutes. Insect mortality was evaluated 24 hours after treatment and fruit quality was evaluated after treatment and after 7 and 14 days of storage at 1 °C. No larvae survived at the 50 and 51.6 °C treatments. Fruit color of non-infested cherries was darkened as temperature increased. Stem color was severely impacted after 7 days of storage, even in a warm water bath of 38 °C for 6 minutes, as was fruit firmness at the same treatment. Fruit quality loss increased after 14 days of storage, compared to after 7 days of storage. The amount of pitting and bruising of cherries increased with temperature and again this increase was more evident after 14 days of storage.