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Amots Hetzroni, Denys J. Charles, Jules Janick and James E. Simon

A prototype of a nondestructive electronic sensory system (electronic sniffer) that responds to volatile gases emitted by fruit during ripening was developed. The electronic sniffer is based upon four semiconductor gas sensors designed to react with a range of reductive gases, including aromatic volatiles. In 1994, we examined the potential of using the electronic sniffer as a tool to nondestructively determine ripeness in `Golden Delicious' and `Goldrush' apples. Fruit were harvested weekly from 19 Sept. to 17 Oct. (`Golden Delicious') and 27 Sept. to 18 Nov. (`Goldrush'). Each week, apples of each cultivar were evaluated individually for skin color, weight size, and headspace volatiles. Each fruit was then evaluated by the electronic sniffer, and headspace ethylene was sampled from air within the testing box. Individual fruits were then evaluated for total soluble solids, firmness, pH, total acidity, and starch index value. The electronic sniffer was able to distinguish and accurately classify the apples into three ripeness stages (immature, ripe, and over-ripe). Improved results were obtained when multiple gas sensors were used rather than a single gas sensor.

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Molly Felts, Renee T. Threlfall, John R. Clark and Margaret L. Worthington

. Muscadine grapes ripen asynchronously, but abscise easily from the stem when ripe. The six genotypes were harvested at optimal commercial ripeness (removed easily from the stem, shiny, and fully colored) for fresh-market muscadine grapes. The fruit was free

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R.L. Shewfelt, J.K. Brecht and C.N. Thai

Tomato ripeness is currently assessed by a subjective visual classification scheme based on external color while maturity of green fruit is based on a destructive evaluation of internal locule development. In an effort to develop an objective method of tomato maturity and ripeness classification, external color measurements were performed on fresh, sized (6×7) `mature-green' tomatoes (cv “Sunny') initially and through ripening using a Gardner XL-845 colorimeter. Hue angle (tan-1 b/a, designated θ) provided the best objective means of ripeness classification with proposed ranges for mature-green (θ>114), breaker (101<θ<114), turning (85<θ<101), pink (64<θ<85), light red (36<θ<64) and red (θ<36) classes using average hue at the circumference. Hue angle at the blossom end was 2-12° lower than at the circumference due to initiation of color development at the blossom end. Colorimetry was not able to distinguish differences in physiological maturity of mature-green tomatoes as determined by the length of time required to develop from mature-green to breaker which varied from 1 to 22 days in the test.

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R.J. Bender, J.K. Brecht, D.J. Huber and S.A. Sargent

Tree-ripe `Tommy Atkins' mangoes were not injured during storage in controlled atmospheres (CA) for 21 days at 8°C, and the fruit resumed ripening after transfer to air at 20°C (Bender et al., 1995). In our study, tree-ripe `Keitt' mangoes were stored at 5 and 8°C in either 10% or 25% CO2 combined with 5% O2 with control fruit maintained in air. Control fruit had higher percentages of electrolyte leakage than CO2-treated fruit at transfer from the CA and after 3 days in air at 20°C. Fruit stored in 25% CO2 at 5°C had significantly higher concentrations of 1-aminocyclopropane-1-carboxylic acid (ACC), over 0.5 nmol ACC/g fresh weight in mesocarp tissue. All the other treatments had similar ACC levels (<0.3 nmol/g fresh weight) after 21 days in CA. Ethylene production rates at both temperatures were significantly lower in the 10% CO2 treatment than in control fruit and were not detectable in 25% CO2. Ethylene production was similar in all treatments after transfer to air. Fruit from the 25% CO2 treatment at 5°C developed dull, green-grayish spots on the epidermis, but otherwise epidermal color, as determined by chroma and hue angles, did not differ among the treatments. There also were no differences in flesh color and flesh firmness.

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Edgar L. Vinson III, Floyd M. Woods, Joseph M. Kemble, Penelope Perkins-Veazie, Angela Davis and J. Raymond Kessler

( U.S. Department of Agriculture, 2006 ). Watermelon fails to increase in sugars after being removed from the vine so it must be harvested near full ripeness ( Rushing et al., 2001 ). Watermelon fruit have few external indicators of ripeness. Unlike

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E.V. Wann

Tissue firmness of ripe tomatoes is controlled by cell wall integrity of the fruit tissue and by the enzymatic softening that normally occurs during ripening. This study was conducted to determine the physical characteristics of cells and tissues of mature green (MG) and ripe fruit that might account for differences in firmness between `Rutgers' (normal), `Flora-Dade' (Firm), and two mutant lines called high-pigment (T4065 hp) and dark-green (T4099 dg), both of which possess extra firm fruit. Fruit samples were tested for resistance to a force applied to whole fruit and to sections of the pericarp tissue and by stress-relaxation analysis. Determinations were also made of cell density and cell wall content within the pericarp tissue. Fruit of mutant lines had firmer tissue than either `Rutgers' or `Flora-Dade' at MG or ripe. Whole fruit compression measurements showed that T4099 dg was firmer than T4065 hp or `Rutgers' at MG and firmer than `Flora-Dade' and `Rutgers' when ripe. Whole fruit of `Flora-Dade' were significantly firmer than `Rutgers' at MG and ripe. Firmness measured by compressive strength also showed that mutant lines had firmer pericarp tissue than the wild types at both MG and ripe stages. Stress-relaxation analysis showed that MG fruit of T4099 dg had greater tissue elasticity than `Rutgers' or `Flora-Dade'. Ripe fruit of both mutant lines had more tissue elasticity than wild types. There were no apparent differences among the genotypes due to tissue relaxation. From these analyses, tissue elasticity appears to be a significant parameter in determining tissue firmness in the tomato genotypes used in this study. Firmness and textural quality of ripe tomatoes appeared to be dependent on elasticity of the pericarp tissue and on the level of enzymatic softening during ripening.

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Mikal E. Saltveit Jr. and Abdel R. Sharaf

Tomato fruit (Lycopersicon esculentum Mill., cv. Castelmart) were harvested at various degrees of ripeness and exposed to ethanol vapor at 0, 2, or 4, ml·kg-1 in a 20-liter jar for 0, 2, 4, or 6 hours at 20C. Ripening was measured as changes in subjective color and in firmness and production of CO2 and ethylene. The soluble solids concentration (percent), titratable acidity (percent), and pH were measured at the end of the storage period when the fruit were red-ripe. Ethanol's inhibition of ripening was not confined to mature-green fruit, but also inhibited reddening of breaker, turning, and pink fruits. Storage of mature-green fruit at 20, 15, or 12C after treatment with 0 or 2 ml ethanol/kg at 20C prolonged the delay in ripening for 5, 6, and 7 days, respectively, compared with controls. There was no reduction in the quality of these fruit when they were red-ripe, even though there was an 11-day difference between the time the 20C control and the 12C-treated fruit became red-ripe. An informal panel did not detect any differences in flavor between these control and ethanol-treated fruit that were red-ripe. Increasing the duration of exposure to ethanol vapors from 2 to 6 hours had a pronounced effect on ethylene and CO2 production, but it did not significantly prolong the inhibition of ripening of mature-green fruit nor did it change their rate of softening during ripening. Increasing the temperature during exposure increased the effectiveness of ethanol, with the same level of inhibition produced by 6 hours at 20C, 4 hours at 25C, or 2 hours at 30C. Postharvest use of ethanol vapor to retard ripening may be a useful technique to extend the market life of tomato fruit.

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John C. Beaulieu, Karen L. Bett, Elaine T. Champagne, Daphne A. Ingram, James A. Miller and Ralph Scorza

Many consumers do not buy peaches due to the fuzzy skin and seed stone and because out-of-season peaches do not possess optimum tree-ripe flavor. The feasibility of using a non-browning freestone peach to deliver high-quality fresh-cut products was investigated. Changes in fresh-cut flavor, texture, and postharvest attributes of commercial-ripe (CR) vs. tree-ripe (TR) harvested and shipped `Bounty' peach was assessed. Fresh-cut CR wedges had an initial firmness of 20.9 N, whereas TR wedges had 11.2 N. On day 2, firmness decreased roughly 3% to 12% and 35% to 45% for CR and TR wedges held at 1 °C, respectively. By day 5, CR wedges hardened (24.5 N) whereas TR did not return to their initial firmness; increasing marginally through day 7. Sensory panel hardness for CR did not change through storage, but with TR wedges, hardness decreased through day 2 then increased until day 7. Little variation was noted in the initial soluble solids for CR vs. TR wedges (11.7, vs. 11.4 °Brix, respectively). After 7 days storage, °Brix decreased 7.5% to 12% in CR and 4.5% to 12% in TR wedges. Yellow flesh color (b*) decreased in all CR and TR treatments through storage. Flavor compounds in expressed juice were analyzed by solid phase microextraction with GC-MS. Several peaks were identified that may be associated with flavor-related changes that occurred during storage. For example, low molecular weight acetates and 6C compounds almost disappeared during storage, whereas short chain fatty acids, lactones, and palmitic acid increased markedly through storage. In TR, the “fruity” descriptor decreased throughout storage and “sweet aromatic” increased slightly (day 2) then decreased through day 7.

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R.J. Bender and J.K. Brecht

Mangoes for long-distance markets are harvested at the mature-green stage and shipped in refrigerated containers. Shipment under controlled atmosphere is still tentative, and the CO2 concentrations used are relatively low (maximum 10%), although mangoes have been reported as being less-sensitive to elevated CO2 than other tropical fruits. In the present study, CO2 concentrations of 10%, 15%, 25%, 35%, and 45% combined with 5% O2 were used to store mangoes. Mature-green `Tommy Atkins' were stored for 21 days at 12C, followed by air storage at 20C for 5 days. Tree-ripe mangoes were stored at 8 or 12C under the same conditions. Ethanol production rates increased along with increasing CO2 concentrations. However, only 35% and 45% CO2 atmospheres inflicted damage. Color development was severely inhibited under those treatments. Lower CO2 treatments, up to 25% in the storage atmosphere, inhibited skin color development and ethylene biosynthesis but, after 5 days in air at 20C, skin color and ethylene production reached control levels. Fruit flesh firmness did not differ among treatments at 12C. Tree ripe mangoes stored in CA at 8C were only significantly firmer than control fruit at transfer from CA to air.

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Jeanine M. Davis

In recent years there has been an increase in the incidence of “gold flecking,” which develops on the surface of ripe tomato fruit. Gold flecking looks like a light sprinkling of gold on the skin of the fruit. There are no lesions and the interior of the fruit is not affected. Usually, gold flecking is barely noticeable. In 1998, however, gold flecking was severe enough in some cases to cause economic losses. It has been suggested that gold flecking is due to use of the insecticide Asana or it may be a genetic disorder. The objective here was to determine if gold flecking is caused by Asana and/or is cultivar-dependent. Treatments consisted of three cultivars (Mountain Fresh, Celebrity, and Mountain Pride) and four insecticides (Asana XL, Karate 1 EC, Thiodan 50 WP, and a water control). There were two plantings. Only red fruit was harvested. For both plantings, there was more gold flecking in the control than any of the insecticide treatments. There were no differences among the insecticides. For the early planting, `Mountain Fresh' had more gold fleck than the other cultivars. In the late planting, there were no differences between cultivars. This study demonstrates that Asana was not responsible for gold flecking and actually reduced it compared to the control. These results also suggest that insects may play a role in gold flecking.