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Guiwen Chene, Carlos Crisosto and David Garner

During the 1993 and 1994 seasons, the response of Kiwifruit (Actinidia deliciosa var. Hayward) flesh softening to exogenous ethylene applications was studied on fruit collected weekly from cold storage and directly from the vines. Fruit samples from both sources, were induced to ripen with and without ethylene preconditioning treatment (10 ppm, 24h at 0C).

During the first 3 weeks of fruit collection, flesh firmness decreased and SSC accumulation increased faster in ethylene treated kiwifruit than in the untreated. After this period, when kiwifruit had close to 9 pounds flesh firmness, ethylene treated and untreated kiwifruit softened at the same rate. Ethylene treatment did not enhance kiwifruit CO2 and ethylene production except at the first harvest time. Furthermore, ethylene treated kiwifruit did not have higher respiration and ethylene rates than untreated kiwifruit when measured at 0, 5 and 20C.

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David Garner, Carlos H. Crisosto and Eric Otieza

`Snow King' peaches (Prunus persica) harvested at commercial maturity were subjected to different carbon dioxide (CO2) and oxygen (O2) atmosphere combinations for a 2-week simulated transportation [0 °C (32 °F)] period after 1 week of cold storage in air (0 °C). In 1998, air or 5%, 10%, 15%, or 20% CO2 combined with 3% or 6% O2 were used during shipment. The trial was repeated in 1999, but for this year half of the fruit were treated with a 50 mg·L-1 (ppm) aminoethoxyvinylglycine (AVG) postharvest dip before storage and simulated shipment. In addition, O2 levels during simulated shipment were reduced to 1.5% and 3%. At harvest and after the 2-week simulated shipment, fruit flesh firmness, soluble solids concentration (SSC), titratable acidity (TA), and chilling injury (CI) were evaluated. For both years, there were no significant differences in quality attributes among the different treatments after the simulated shipment period. SSC and TA did not change during 5 days postshipment ripening at 20 °C (68 °F). In 1998 all treatments softened rapidly during the postshipment ripening at 20 °C, and were ready to eat [13 N (1 N = 0.225 lb force)] after 3 days. In 1999, both the high CO2 atmospheres during shipment and the AVG postharvest dip slowed the rate of softening during subsequent ripening at 20 °C. With respect to fruit softening, there was significant interaction between storage atmosphere and AVG treatment. AVG-treated fruit shipped under a 20% CO2 + 3% O2 atmosphere did not soften to the transfer point (firmness = 27 N) within our 5-day ripening period, while fruit not treated with AVG and shipped under the same atmosphere softened to the transfer point in 3 days. Control fruit (no AVG + air shipment) softened to the transfer point in 2 days. Our previous work found that when white flesh peaches soften to less than 27 N firmness they become very susceptible to impact bruise injury during retail distribution. We call this critical level of fruit flesh firmness the transfer point. Symptoms of CI, low O2, or high CO2 injury were not observed in any treatment in either year.

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Carlos H. Crisosto, David Garner and Gayle Crisosto

Efficacy of controlled atmosphere (CA) conditions for decay control in 'Thompson Seedless' table grapes was evaluated during the 1998-2000 seasons. During the 1998 season, early (16.5% soluble solids concentration = SSC) and late harvested (19% SSC) grapes were exposed to 5%, 10%, 15%, 20%, or 25% CO2 combined with 3%, 6%, and 12% O2. In 1999 and 2000, 10% or 15% CO2 combined with 3%, 6%, or 12% O2 were used. In all trials, fruit were initially SO2 fumigated and air-stored grapes were used as controls. Storage atmospheres did not affect SSC, titratable acidity (TA), or sugar-to-acid ratio (SSC: TA). The main storage limitations for early harvested 'Thompson Seedless' table grapes were “off flavor” and rachis and berry browning development, which resulted from exposure to >10% CO2. However, ≥15% CO2 was needed to control total decay and nesting development independent of O2 concentrations. High carbon dioxide atmospheres (15% to 25%) were more effective in decay control without detrimental effects on quality when late harvested grapes were used. The combination of 15% CO2 with 3%, 6%, or 12% O2 is suggested for up to 3 months storage only for late harvested 'Thompson Seedless' table grapes; it should not be used for early harvested grapes.

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Carlos H. Crisosto, Lluís Palou, David Garner and Donald A. Armson

Reduced doses of sulfur dioxide (SO2) were evaluated for the fumigation of marine containers with respect to the concentration × time (CT) product and gas penetration. Two commercial export containers were loaded at 32 °F (0 °C) with 20 metric pallets [40 × 48 inches (102.5 × 123.1 cm)] comprised of 72 expanded polystyrene foam boxes (12 tiers, 6 boxes/tier) of table grapes (Vitis vinifera) and fumigated with 1.0 and 0.5 lb (0.454 and 0.227 kg) SO2, respectively. A third marine container was loaded with 20 metric pallets comprised of 84 plastic boxes of table grapes (14 tiers, 6 boxes/tier) and fumigated with 0.25 lb (0.113 kg) SO2. The boxes contained 16 lb (7.3 kg) of table grapes distributed in nine polyethylene cluster bagsenclosed in a perforated polyethylene box liner. Fumigations were performed through the bottom seal of the rear door from pre-weighed compressed SO2 cylinders. CT product was calculated after taking samples of the atmosphere in the container every 5 to 10 min and measuring the ambient SO2 concentration with a gas sampling pump and colorimetric dosimeter tubes. Pallet and box penetration of the gas was assessed by placing passive colorimetric SO2 dosimeters inside the cluster bags in boxes located in both the third and ninth center boxes from the top of pallets located in the front, center, and rear of the load. Fumigations with 1.0, 0.5, and 0.25 lb SO2, with calculated CT products at 32 °F of 925, 360, and 40 ppm-h (μL·L-1·h-1) respectively, were found to provide excessive, adequate, and insufficient SO2 doses.

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Carlos H. Crisosto, David Garner, Jim Doyle and Kevin R. Day

Respiration rate and bruising incidence were assessed in new cherry (Prunus avium L.) cultivars adapted to high temperatures. `Bing', `Brooks', `Tulare', and `King' respiration rates were evaluated at 0,5,10, and 20C, and bruising susceptibilities at 0, 10, 20, and 30C. `Bing' was the least susceptible to bruising and had the lowest respiration rate at all temperatures. Respiration rate increased with temperature in all cultivars. Impact bruising damage was greatest in all cultivars when fruit flesh was below 10C. Vibration damage was not influenced by fruit temperature. Our results suggest that the cherry cultivars assessed should be handled at temperatures between 10 and 20C during packing to minimize bruising damage. Due to increased respiration rates at higher temperatures, however, fruit should be cooled to 0C within 4 to 6 hours after harvest.

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Lauren Garner, Desmond Mortley, Philip Loretan, Audrey Trotman and Pauline David

An experiment was conducted in a greenhouse environment to determine the relationship between type of cutting and planting depth on sweetpotato [Ipomea batatas (L) Lam] storage root yield using the nutrient film technique. Vine cuttings of the cultivar 'TI-155' were planted in growth channels (122×15×15 cm) in modified half Hoagland's solution. Treatments consisted of cuttings with all leaves and shoot apex removed with two nodes inserted (2NB), cuttings with all leaves and shoot apex removed with five nodes inserted (5NB). and cuttings with four leaves and the shoot apex remaining with two nodes inserted (2NB-L). Plants were harvested 130 days after planting and yield data was taken. Plants in 2NB-L had a significantly lower percent dry matter than those of 2NB. Neither cutting type nor planting depth affected yield or yield related parameters.

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Guiwen Cheng, Carlos Crisosto, David Garner, Scott Johnson and Bob Beede

The roles of genetic makeup and `orchard environment' on fruit skin discoloration (SD) were studied on peaches and nectarines. Our data showed that the SD incidence (SDI) varied among cultivars in the same orchard and orchards with the same cultivar. Differences in SD susceptibility were examined on whole fruit and skin disks by using SD-inducing treatments including combinations of physical injury and dipping in different solutions (pH, and metal ions). High SDI was associated with physical injury, high pH, and high metal ion concentration. With the exception of N, the amount of macro- and micronutrients in unwashed fruit skin was not correlated with the SDI. Preharvest sprays influenced the SDI. The peach variety with the highest SDI had the highest total soluble phenols. Total soluble phenols and anthocyanins, however, did not show a strong relationship with the SDI among all cultivars studied. Lack of correlation with total soluble phenols does not exclude the possibility that SD may relate to specific phenol(s).

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Carlos H. Crisosto, David Slaughter, R. Scott Johnson, Luis Cid and David Garner

Maximum maturity indices for different packinghouse conditions based on cultivar critical bruising thresholds and bruising potentials were developed for stone fruit cultivars. The critical bruising thresholds, based on fruit firmness, and the bruising probabilities varied among stone fruit cultivars. In general, plums tolerated more physical abuse than yellow-fl esh peach, nectarine, and white-flesh peach cultivars. Impact location on the fruit was an important factor in the determination of critical bruising thresholds. Potential sources of bruising damage during fruit packing were located using an accelerometer (IS-100). A survey of different packinghouses revealed that bruising potentials varied from 21 to 206 G. Bruising potential was reduced by adding padding material to the packinglines, minimizing height differences at transfer points, synchronizing timing between components, and reducing the operating speed. Bruising probabilities for the most-susceptible California-grown cultivars at different velocities and Gs have been developed. Development of a practical sampling protocol to determine fruit firmness during maturation was studied.

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Sanliang Gu, Carlos H. Crisosto, R. Scott Johnson, Robert C. Cochran and David Garner

Fruit from 8 `Hayward' kiwifruit vineyards in central California were harvested at 2 week intervals after soluble solids content (SSC) reached 6% and subjected to 4 and 6 months of storage at 0°C in an ethylene free environment. Fruit characteristics at harvest and postharvest performance varied considerably among locations. Fruit stored for 6 months had the same fresh weight, less flesh firmness and higher SSC, than the 4 months storage. Later harvested fruit had greater fruit flesh firmness and higher SSC after storage. SSC after storage was predictable based on ripe soluble solids content (RSSC) at harvest. Summer pruning reduced while soil nitrogen application increased fruit SSC.

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Carlos H. Crisosto, David Garner, Harry L. Andris and Kevin R. Day

A commercial controlled delayed cooling or preconditioning treatment was developed to extend peach (Prunus persica) market life of the most popular California peach cultivars. A 24 to 48 h cooling delay at 68 °F (20.0 °C) was the most effective treatment for extending market life of internal breakdown susceptible peaches without causing fruit deterioration. This treatment increased minimum market life by up to 2 weeks in the cultivars tested. Weight loss and softening occurred during the controlled delayed cooling treatments, but did not reduce fruit quality. Detailed monitoring of these fruit quality changes during the delayed cooling period and proper use of fungicides is highly recommended for success in this new fruit delivery system. Rapid cooling after preconditioning is important to stop further fruit deterioration such as flesh softening, senescence, decay and weight loss. Controlled delayed cooling can also be used to pre-ripen susceptible and nonsusceptible peaches to deliver a ready-to-buy product to the consumer.