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Jinhe Bai

Superficial scald of `d'Anjou' pears usually develops after storage of 2 months or longer. MCP application controls scald; however, fruit lose their ripening capacity if the dosage is >30 ppb, but lower dosages cannot control scald substantially. In this study, fruit treated with or without 25 ppb MCP within 2 d after harvest were stored at –1 °C for up to 5 months. After 1, 7, 30, or 70 d of storage, part of the fruit were pulled from storage and treated with 1000 ppm ethoxyquin line spray and immediately returned to the storage, left untreated as non-ethoxyquin control. Incidence of superficial scald along with the concentrations of α-farnesene and conjugated trienes (CTs), and the ripening capacity of fruit were investigated after 3, 4, and 5 months storage. All fruit ripened properly within 7 d of conditioning at room temperature regardless of treatments. Both of MCP or ethoxyquin-1d (ethoxyquin was applied after 1 day storage at –1 °C) alone controlled scald for only 3 months; however, MCP + ethoxyquin controlled scald for 5 months, whenever ethoxyquin was applied between 1 to 70 d after storage. Thus, with 25 ppb MCP treatment, which is simple, with rapid and mass treatment available, a delayed application (up to 70 d) of ethoxyquin becomes effective to control scald. Furthermore, the later application of ethoxyquin within 70 d after MCP treatment, the less incidence of scald was observed. Scald is caused by the CTs oxidation products of α-farnesene. MCP and ethoxyquin inhibited accumulation of CTs of fruit peel by different mechanisms. MCP inhibited the production by influencing ethylene production through control of α-farnesene synthesis; however, ethoxyquin worked by inhibiting the oxidation of α-farnesene to the CTs.

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Jin-He Bai and Alley E. Watada

A study was made to determine if induction of modified atmosphere at the time of packaging would be of a benefit to the quality of fresh-cut honeydew cubes because the desired gas levels are not attained immediately or at all during the short holding period in modified-atmosphere packages. Fresh-cut honeydew cubes (2-cm cube) were placed in a plastic container underlaid with a water absorbent packet and the container was sealed with a film. The film is coextruded polystyrene and polyethylene (Cryovac), which had oxygen transmission rates of 1448 and 1903ml/m2 per day per atm at 5 °C and 10 °C, respectively. The sealed packages were given one of the following three treatments: 1) the packages were allowed to form their own natural modified atmosphere (nMAP), 2) the internal atmosphere of the packages was flushed with a gas mixture of 5% O2 + 5% CO2 (iMAP), 3) the film was perforated with a needle to have ten 1.5-mm holes (PFP). The packages were stored at 5 °C, 2 days at 5 °C, and transferred to 10 °C or at 10 °C for 2, 4, 7, 9, or 11 days. Quality attributes and microbial population were analyzed after each holding period. The average gas mixture equilibrated to 7% O2 and 9.5% CO2 in nMAP, was unchanged from the induced atmosphere in iMAP, and was close to the ambient condition (air) in PFP. Honeydew cubes were marketable on days 11, 4, and 4 when held in nMAP; on days 11, 4, and 7 when held in iMAP; and unsalable on days 9, 4, and 7 when held in PFP at 5 °C, 10 °C or transferred to 10 °C, respectively. Development of water-soaked lesions and sour odor were the main factor affecting marketability of the cubes. The decreasing pH, chroma and `L' values and increasing hue angle, mesophilic aerobic microrganism, and yeast population was retarded in both of nMAP and iMAP.

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Xinhua Yin, Jinhe Bai and Clark F. Seavert

Single broadcast application of nitrogen (N) and phosphorus (P) on the soil surface results in low use efficiency of applied N and P in pear (Pyrus communis) production systems in Oregon and the Pacific northwestern United States. A field experiment was conducted from 2005 through 2006 to evaluate the effects of split fertigation and band placement as alternate N and P management practices in ‘Anjou’ pears growing on a Parkdale loam soil near Parkdale, OR. Measurement and analysis of tree nutrition, fruit yield, quality, and storability, as well as indigenous soil nutrient supply was the scope of the experiment. To evaluate fertilizer management practices on pear growth and productivity, the following four treatments were tested with a randomized complete block design replicated four times: 1) broadcast application of N and P on the soil surface in a 10-ft-wide, weed-free strip centered on the tree row, 2) band placement of N and P on both sides of tree rows in 1 × 1-ft ditches (width × depth), 3) 1 × 1-ft ditches were dug using the band placement equipment, the dug soil was completed returned to the ditch without any fertilizer, and the broadcast application of N and P on the soil surface was applied on a 10-ft-wide, weed-free strip centered on the tree row, and 4) fertigation of N and P split into five equal applications throughout the growing season. Nitrogen and P fertilizers were applied to treatments 1, 2, and 3 at 100 lb/acre N and 55 lb/acre P, while treatment 4 received only 80 lb/acre N and 44 lb/acre P. The 2-year average results show leaf N and P concentrations in the fall were increased by 10.0% and 10.6%, respectively, with split fertigation compared with broadcast application on the soil surface. Band placement increased leaf N by 7.1% relative to broadcast application on the soil surface with soil disturbance caused by band placement. Split fertigation and band placement slightly increased fruit yield, but increased marketable fruit (the total of excellent and very slightly scalded fruit) by 20.9% and 11.1% (absolute value) when compared with broadcast application of N and P and broadcast application of N and P with soil disturbance caused by band placement, respectively, and after 3 months of cold storage. No detrimental effects on fruit weight or reduction in soil amino sugar N were observed from lowering the N and P application rates by 20% with split fertigation. Overall, split fertigation and band placement of N and P can be used to replace single broadcast application on the soil surface on pear orchards to reduce fruit superficial scald during cold storage and improve the use efficiency of applied N and P in the mid-Columbia region of Oregon.

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Xinhua Yin, Clark Seavert and Jinhe Bai

Responses of adult pear to the integrated N fertigation and drip irrigation system have not been documented in Oregon. A field trial was conducted on adult pear at the Mid-Columbia Agricultural Research and Extension Center, Hood River, Ore., in 2005. Two N and water management systems (integrated N fertigation and drip irrigation system; and broadcast application of dry N fertilizer to the soil surface and microsprinkler irrigation system) were compared on pear cultivars of Bartlett and Golden Russet Bosc, and rootstocks of OH×F97 and OH×F87. The responses of these cultivars and rootstocks to the integrated N fertigation and drip irrigation system were similar. The integrated N fertigation and drip irrigation system consumed 1450 m3·ha-1 of irrigation water during the entire season from May to September, reducing irrigation water use by 73% compared with 5297 m3·ha-1 under the current system—broadcast application of dry N fertilizer to the soil surface and microsprinkler irrigation system averaged over the four cultivar and rootstock combinations. The fruit yield was statistically similar for the integrated N fertigation and drip irrigation system and the broadcast application of dry N fertilizer and microsprinkler irrigation system on the average of the four cultivars and rootstocks. Differences in fruit size and color were negligible between the two N and irrigation management systems. Overall, our results suggest that adopting the integrated N fertigation and drip irrigation system does not cause significant reduction in yield or quality of adult pear; the integrated N fertigation and drip irrigation system could be a profitable and environmentally sound management alternative for pear production.

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Jinhe Bai, Kristi Barckley and John Manthey

Pear texture is similar to that of apple—firm and crispy—and is one of the potential alternatives to apple. However, at a crispy stage the taste is flat. Improving the taste of pears is considered the key to the success of pear salad. This study evaluated the effect of harvest maturity on the quality of pear salad. Fruit were harvested at commercial maturity or 1 month delayed. After 2 and 5 months (1 and 4 months for delayed harvested fruit) of storage at –1 °C, fruit were sliced (eight to 10 wedges per fruit), treated with an anti-browning dip, packaged in zip-lock bags (10 pieces per bag), and stored at 1 °C for up to 21 days. Delayed harvested fruit were larger in size (≈12.5% increase in weight), had lower flesh firmness (≈5 N decrease), lower titratable acidity content (≈20% decrease), and a lower phenolic content (≈45% decrease in pulp). There was no significant difference in soluble solids content. After 2 months of storage, ethylene production and respiration rate were initially lower in delayed harvested fruit in either the intact fruit or cut slices, but tended to similar after 7 days in storage. Sensory evaluation results show that about 80% of the panel preferred delayed-harvested fruit over commercial harvest, especially in terms of visual quality (71% to 92%), sweetness (75% to 93%), taste (69% to 92%), texture of skin (61% to 92%), texture of flesh (53% to 92%), and overall quality (73% to 92%) during 21 days of storage at 1 °C. After 5 months of storage, cutting surface was dry-looking in delayed harvested fruit. However, sensory evaluation showed panels still preferred the delayed-harvested fruit. The results indicate that salad quality of pears can be improved by delaying harvest.

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Xinhua Yin, Clark Seavert and Jinhe Bai

The effects of in-row groundcover and drip irrigation on mineral nutrition and productivity of sweet cherry are largely unknown in the Pacific Northwest. A field experiment was initialized on the Mel Omeg orchard at The Dalles, Ore., in 2005. This orchard had been managed under microsprinkler irrigation and in-row herbicide application since its establishment in 1998. Two irrigation systems (drip irrigation, microsprinkler irrigation) and four in-row ground management systems (straw mulch, white fabric cover, black fabric cover, and no cover with herbicide applications) were evaluated in a split-plot design with four replicates. Drip irrigation reduced irrigation water consumption by 74% relative to microsprinkler during the entire season from May to September. Compared with no cover, black fabric lowered water use by 8%, and straw mulch and white fabric had a 1% to 3% reduction in water use. Fruit yield was similar for drip irrigation and microsprinkler. There was a trend of yield increase with groundcovers relative to no cover. Fruit firmness, size, and sugar content did not differ regardless of irrigation or groundcover systems. Drip irrigation increased marketable fruits by 5% (absolute value) via reducing fruit surface pitting compared with microsprinkler. Differences in soil-available N, P, K, Ca, Mg, S, B, Zn, Mn, Cu, pH, and organic matter were negligible between the two irrigation systems and among the four groundcover treatments. However, drip irrigation resulted in slightly lower concentrations of N, P, K, Ca, B, and Mn in leaf than microsprinkler. Overall, our results suggest that in-row straw mulch and fabric covers and drip irrigation could be feasible management alternatives for sweet cherry production in the Pacific Northwest.

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Hong Chen, Greg McCollum, Elizabeth Baldwin and Jinhe Bai

This study evaluated the effects of huanglongbing (HLB) symptom severity on fruit detachment force (FDF) and fruit mechanical properties in sweet oranges (Citrus sinensis) as indicators of potential HLB-influenced preharvest fruit drop and postharvest damage and breakdown. FDF for fruit from HLB-asymptomatic trees (AS) was substantially greater than for fruits from HLB-symptomatic trees or branches. Fruit hardness, resilience, springiness, and cohesiveness values, measured by texture profile analysis (TPA), represent various aspects of fruit firmness and recovery capacity once compressed, and were lower in HLB-symptomatic fruits in comparison with AS fruits. On the other hand, puncture force, toughness, and deformation values, measured by a puncture test and representing peel toughness, were higher in HLB-symptomatic fruits than in the AS fruits. The results indicate that fruits from severely HLB-symptomatic sweet orange trees are more likely to have problems with preharvest fruit drop, and postharvest pressure damage and breakdown, but may have less puncture damage in harvesting, transportation, packing, and juice processing.

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Xiuxiu Sun, Elizabeth Baldwin, Mark Ritenour, Robert Hagenmaier and Jinhe Bai

In Florida, early season citrus fruits usually reach full maturity in terms of internal quality while their peel often does not turn to orange color after degreening due to insufficient buildup of carotenoids. For huanglongbing (HLB)-affected orange trees, the fruit may never turn orange during the entire harvest season, despite any cold weather. Improvement of early season citrus peel color is important to the citrus industry to better meet consumer expectations. Occasionally, packinghouses apply a dye, Citrus Red No. 2 (CR2), to improve the surface color of oranges, temples, and tangelos before applying a fruit wax to impart shine, retain moisture, and slow fruit senescence. In a previous report, we determined that paprika and annatto extracts are comparable to CR2 as natural colorant alternatives. In this research, the goal was to formulate a natural colorant [annatto, paprika, or paprika oleoresin (PO)]-containing carnauba wax coating. The coatings were first evaluated for color, shine, moisture retention, respiration rate, ethylene production, and internal gas content. Control fruit were coated with carnauba wax alone, or dyed with CR2 then coated with carnauba wax. The effects were assessed under different temperature and light exposure conditions to simulate commercial storage and marketing. The results showed that a one-step application of paprika-containing carnauba wax was comparable to the two-step (“CR2 then wax”) applications in improving fruit appearance and modification of internal gas composition.

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Jinhe Bai*, Paul Chen, Elizabeth Baldwin and James Mattheis

`Bartlett' pears were treated with 300 nL·L-1 1-MCP at 20°C for 24 h shortly after harvest, and were stored at -1 °C in either regular atmosphere (RA) or controlled atmosphere (CA: 1.5 kPa O2 / 0.5 kPa CO2). After 2 and 4 months of RA storage, or 4 months of CA storage, fruit were pre-conditioned at 10 °C, 15 °C or 20 °C for 5, 10, or 20 days, respectively. Pre-conditioned fruit were then held at 20 °C for 14 days to simulate marketing conditions. Flesh firmness (FF) and extractable juice (EJ) were monitored during the marketing period. The optimal stage of ripeness for `Bartlett' pears was defined to be when FF decreases to 27 N and EJ decreases to 55 mL/100 g. The proper pre-conditioning combinations of temperature and duration were 15 °C or 20 °C for 10 d or 10 °C for 20 d if the fruit had been stored in RA for 2 months, 10 °C or 15 °C for 5 d if the fruit had been in RA for 4 months, and 20 °C for 10 d or 10°C for 20 d if the fruit had been in CA for 4 months, for which combinations the fruit ripened within a week and maintained quality for 14 days at 20 °C. The treatment combinations of lower temperature and/or shorter duration times in pre-conditioning delayed the ripening response of the fruit, and combinations of higher temperature and/or longer duration times in pre-conditioning resulted in a shorter marketing life because of senescence breakdown, in comparison the optimal combinations mentioned above. These results indicate that pre-conditioning regimes for 1-MCP treated `Bartlett' pears are storage atmosphere and time dependent. Generally, CA stored fruit needed more preconditioning (in terms of higher temperature and/or longer duration) than did RA stored fruit.

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Jinhe Bai, Elizabeth Baldwin, Jack Hearn, Randy Driggers and Ed Stover

Six ‘Ambersweet’-derived hybrids, similar to sweet orange fruit size, color, and taste and potential as new sweet orange cultivars, were selected to determine their fruit categorization by comparison of their volatile profiles with the parent and ‘Hamlin’, a typical sweet orange. All hybrids are at least ½ sweet orange and varying amounts of mandarin, grapefruit, Poncirus trifoliata, and sour orange in each pedigree. In total, 135 volatiles were detected in the eight hybrid lines/commercial cultivars over two harvests, and 20 compounds were detected in all samples, including terpenes (limonene, β-myrcene, α-pinene, α-terpinene, α-terpineol, and linalool), esters (ethyl butanote, ethyl pentanoate, and ethyl acetate), aldehydes (acetaldehyde, hexanal, and nonanal), and alcohols (ethanol and hexanol). Total abundance of volatiles in January-harvested fruits averaged 30% higher than for fruits of the same trees harvested in November. ‘Ambersweet’ contained the highest total amount of volatiles (mainly as a result of very high levels of monoterpenes), and of them, nootkatone and six other compounds were not detected in any of the hybrids, and some of them were also not detected in ‘Hamlin’. On the other hand, 12 compounds, including pentanal, ethyl 2-butenoate, and ethyl nonanoate, were not detected in ‘Ambersweet’ but were found in ‘Hamlin’ and some of the hybrids. Cluster analysis separated the cultivar/hybrid and harvest time combinations into three clusters. FF-1-76-50, FF-1-76-52 and January FF-1-75-55, all with the same parents (‘Ambersweet’ × FF-1-30-52), were close to FF-1-65-55, but they were separated from ‘Hamlin’ and further separated from ‘Ambersweet’. The cluster containing ‘Hamlin’ has three subclusters: January ‘Hamlin’ and November FF-1-74-14, a hybrid with one-eighth P. trifoliata, which includes a slight off-flavor frequently found in P. trifoliata hybrids, independent of each other, and both were separated from a group of November ‘Hamlin’, FF-1-64-97, and FF-1-75-55. The cluster containing ‘Ambersweet’ included January FF-1-64-97. A principle component analysis (PCA) separated ‘Ambersweet’ from all hybrids and ‘Hamlin’ along the PC1 axis and separated November harvests from January harvests along PC2. This volatile analysis supports the classification of the hybrids as sweet orange.