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E.A. Baldwin, M.O. Nisperos-Carriedo, and M.G. Moshonas

Tomato (Lycopersicon esculentum Mill.) fruit, cvs. Sunny and Solar Set, were analyzed at five ripening stages for ethylene and CO2 production. Homogenates from the same fruit were prepared for determination of color, flavor volatiles, sugars, and organic acids. Changes in the levels of these compounds were compared to the pattern of climacteric ethylene production. Of the flavor volatiles measured, only eugenol decreased during ripening in both cultivars and 1-penten-3-one in `Sunny' tomatoes. Ethanol and trans-2-trans- 4-decadienal levels showed no change or fluctuated as the fruit ripened while all other volatiles measured (cis- 3-hexenol, acetaldehyde, cis- 3-hexenal, trans-2- hexenal, hexenal acetone, 6-methyl-5 -hepten-2-one, geranylacetone, and 2-isobutylthiazole) increased in concentration, peaking in the turning, pink, or red stage of maturity. Synthesis of some volatile compounds occurred simultaneously with that of climacteric ethylene, CO2 and lycopene production. `Solar Set' fruit exhibited higher levels than `Sunny' of all flavor components except ethanol and hexanal in the red stage. There were no differences in organic acid levels between the cultivars; however, `Solar Set' had higher levels of sugars. Changes in acid and sugar levels showed no temporal relationship to climacteric ethylene or CO2 production.

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Dangyang Ke, Lili Zhou, and Adel A. Kader

`Chandler' strawberries (Fragaria ananassa Duck.) were kept in air, 0.25% O2, 21% O2 + 50% CO2, or 0.25 O2 + 50% CO2 (balance N2) at 5C for 1 to 7 days to study the effects of controlled atmospheres (CAs) on volatiles and fermentation enzymes. Concentrations of acetaldehyde, ethanol, ethyl acetate, and ethyl butyrate were greatly increased, while concentrations of isopropyl acetate, propyl acetate, and butyl acetate were reduced by the three CA treatments compared to those of air-control fruit. The CA treatments enhanced activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) but slightly decreased activity of alcohol acetyltransferase (AAT). The results indicate that the enhanced PDC and ADH activities by CA treatments cause ethanol accumulation, which in turn drives the biosynthesis of ethyl esters. The increased ethanol concentration also competes with other alcohols for carboxyl groups for esterification reactions. The reduced AAT activity and limited availability of carboxyl groups due to ethanol competition decrease production of other acetate esters.

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Isabel Pérez-Munuera, Isabel Hernando, Virginia Larrea, Cristina Besada, Lucía Arnal, and Alejandra Salvador

astringency of persimmon; condensation of tannins with acetaldehyde, which is metabolically produced under anaerobic conditions, generates insoluble polymers that are not astringent ( Matsuo and Ito, 1982 ). Removal of astringency without firmness loss is a

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E.A. Baldwin, J.W. Scott, M.A. Einstein, T.M.M. Malundo, B.T. Carr, R.L. Shewfelt, and K.S. Tandon

The major components of flavor in tomato (Lycopersicon esculentum Mill.) and other fruit are thought to be sugars, acids, and flavor volatiles. Tomato overall acceptability, tomato-like flavor, sweetness, and sourness for six to nine tomato cultivars were analyzed by experienced panels using a nine-point scale and by trained descriptive analysis panels using a 15-cm line scale for sweetness, sourness, three to five aroma and three to seven taste descriptors in three seasons. Relationships between sensory data and instrumental analyses, including flavor volatiles, soluble solids (SS), individual sugars converted to sucrose equivalents (SE), titratable acidity (TA), pH, SS/TA, and SE/TA, were established using correlation and multiple linear regression. For instrumental data, SS/TA, SE/TA, TA, and cis-3-hexenol correlated with overall acceptability (P = 0.05); SE, SE/TA (P≤0.03), geranylacetone, 2+3-methylbutanol and 6-methyl-5-hepten-2-one (P = 0.11) with tomato-like flavor; SE, pH, cis-3-hexenal, trans-2-hexenal, hexanal, cis-3-hexenol, geranylacetone, 2+3-methylbutanol, trans-2 heptenal, 6-methyl-5-hepten-2-one, and 1-nitro-2-phenylethane (P≤0.11) with sweetness; and SS, pH, acetaldehyde, aceton, 2-isobutylthiazole, geranlyacetone, β-ionone, ethanol, hexanal and cis-3-hexenal with sourness (P≤0.15) for experienced or trained panel data. Measurements for SS/TA correlated with overall taste (P=0.09) and SS with astringency, bitter aftertaste, and saltiness (P≤0.07) for trained panel data. In addition to the above mentioned flavor volatiles, methanol and 1-penten-3-one significantly affected sensory responses (P = 0.13) for certain aroma descriptors. Levels of aroma compounds affected perception of sweetness and sourness and measurements of SS showed a closer relationship to sourness, astringency, and bitterness than to sweetness.

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Elizabeth Baldwin, Kevin Goodner, and Karen Pritchett

Sugars (sucrose, glucose, fructose, or glucose/fructose in combination) were added to coarsely chopped, deodorized tomato puree, increasing the sugar level of the puree by 2% to 3%. Sugars (equal amounts of glucose and fructose) along with citric acid were also added to another puree, at two different levels, to create a range of sugar: acid ratios (4.88–19.07). This second puree was then spiked with two different levels of aroma volatiles, reported to affect tomato flavor, in order to understand the influence of the sugar: acid background on tomato aroma and taste perception. The tomato puree was presented to a trained panel and was rated for intensity of aroma and taste descriptors on a 15-cm unstructured line scale. For the puree spiked with sugars only, panelists detected differences for overall aroma, ripe aroma, overall taste, sweetness and sourness intensities (P< 0.15). Adding sweet sugars, like fructose and sucrose, resulted in decreased ratings for aroma descriptors, apparently detracting from panelists' perception of aroma. The sugar: acid ratio of the second tomato puree was found to correlate with perception of taste descriptors sweet (+), sour (–), bitter (–) (P< 0.05), and citrus (–) (P< 0.15) for most volatiles tested. Correlations were also found for the sugar: acid ratio with overall aftertaste (–) when the puree was spiked with furanol, trans-2-hexenal, geranylacetone, or acetaldehyde; fruity (+) with β-ionone and linalool; and tropical (+) with cis-3-hexenal and geranylacetone (P< 0.15). The study suggests that increasing taste factors, like sweetness, result in decreased perception of tomato aroma in general, and affect how aroma compounds influence sensory descriptors.

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C.B. Watkins, J.E. Manzano-Mendez, J.F. Nock, J. Zhang, and K.E. Maloney

The tolerances of strawberry fruit to postharvest CO2 treatments is an important factor in assessing their potential for extended storage and marketing, but little information on variation among cultivars is available. We have assessed differences in responses of seven strawberry cultivars (`Annapolis', `Earliglow', `Kent', `Honeoye', `Cavendish', `Jewel', and `Governor Simcoe') to high-CO2 atmospheres. Fruit were harvested at the orange or white tip stage of ripeness, kept in air, or 20% CO2 (in air), and sampled after 1, 2, or 7 days for analysis of firmness, color, and volatile concentrations. Berries from each cultivar were collected on three separate harvest dates. Flesh firmness measurements of all cultivars tested were higher when treated with high CO2, but the degree of firming was affected by cultivar and assessment time. For example, firmness of `Annapolis', `Earliglow', `Honeoye', and `Jewel' was consistently enhanced by CO2, compared with air, during storage. In contrast, firmness of `Kent' was not affected by treatment after 1 day of storage and benefits were relatively slight at each subsequent removal. Red color development of the fruits was affected by cultivar and treatment period, but not by CO2 treatment. Volatile accumulation varied greatly among cultivars. `Annapolis' for example, appears very tolerant of high-CO2 treatment levels as indicated by low accumulations of ethanol, acetaldehyde, and ethyl acetate in the fruit. In contrast, `Kent' and `Governor Simcoe' accumulated large amounts of these compounds. This study indicates that differences in cultivar responses to CO2 should be considered by growers planning to store fruit under these conditions to extend marketing options. Research supported in part by the North American Strawberry Growers Association.

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Ma. Teresa MartÌnez-Damian and Marita I. Cantwell

Spinach is not packed commercially in modified-atmosphere packaging due to difficulties in maintaining beneficial conditions during distribution, where temperature fluctuations can occur. However, low O2 and high CO2 atmospheres can be useful to retard yellowing and deterioration. In two experiments we studied developing and full-size leaves stored at 7.5 °C in air and controlled atmospheres of 0.5% O2 + 10%CO2 and 5%O2 + 10% or 20% CO2. Subjective quality evaluations (visual quality, decay, discoloration, off-odors, and yellowing) and objective evaluations (L*a*b* color values, chlorophyll, pH and titratable acidity, ammonia, and ethanol and acetaldehyde) were conducted every 3 days during 15 days. The developing leaves had higher visual quality and lower off-odor scores during storage than did the full-size leaves. In air storage, leaves were below the limit of salability by day 12. The atmospheres containing 10% CO2 were similarly effective in maintaining the visual quality and greenness of the leaves, and reduced off-odors in developing but not full-size leaves. The 20% CO2 atmosphere resulted in some leaf damage. Ammonia concentrations increased during storage, with lowest and highest concentrations in leaves stored in air and 20% CO2, respectively. Tissue pH only slightly increased from 6.5 in air-stored samples, but increased notably during storage in the controlled atmospheres. At 2.5 and 7.5 °C, a plastic film providing a 5% O2 and 6% CO2 atmosphere resulted in better quality spinach than that obtained with either a 10% O2 and 3% CO2 package atmosphere or the commercial perforated polybag.

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Robert K. Prange, John M. DeLong, Peter A. Harrison, Jerry C. Leyte, and Scott D. McLean

A new chlorophyll fluorescence (F) sensor system called FIRM (fluorescence interactive response monitor) was developed that measures F at low irradiance. This system can produce a theoretical estimate of Fo at zero irradiance for which we have coined a new fluorescence term, Fα. The ability of Fα to detect fruit and vegetable low-O2 stress was tested in short-term (4-day) studies on chlorophyll-containing fruit [apple (Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.), pear (Pyrus communis L.), banana (Musa ×paradisiaca L.), kiwifruit (Actinidia deliciosa C.S. Liang & A.R. Ferguson), mango (Mangifera indica L.), and avocado (Persea americana Mill.)] and vegetables (cabbage (Brassica oleracea L. Capitata Group), green pepper (Capsicum annuum L. Grossum Group), iceberg and romaine lettuce (Lactuca sativa L.)). In all of these fruit and vegetables, Fα was able to indicate the presence of low-O2 stress. As the O2 concentration dropped below threshold values of 0 to 1.4 kPa, depending on the product, the Fα value immediately and dramatically increased. At the end of the short-term study, O2 was increased above the threshold level, whereupon Fα returned to approximately prestressed values. A 9-month study was undertaken with `Summerland McIntosh' apple fruit to determine if storing the fruit at 0.9 kPa O2, the estimated low O2 threshold value determined from Fα, would benefit or damage fruit quality, compared with threshold + 0.3 kPa (1.2 kPa O2) and the lowest recommended CA (1.5 kPa O2). After 9 months, the threshold treatment (0.9 kPa) had the highest firmness, lowest concentration of fermentation volatiles (ethanol, acetaldehyde, ethyl acetate) and lowest total disorders. Sensory rating for off-flavor, flavor and preference indicated no discernible differences among the three treatments.

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R. Porat, B. Weiss, L. Cohen, A. Daus, and E. Cohen

`Oroblanco' is an early-maturing pummelo-grapefruit hybrid (Citrus grandis × C. paradisi). The fruit of this cultivar are usually picked in October and are marketed while their peel color is still green. However, during long-term storage, the fruit turns yellow, and loses much of their commercial value. In a previous study, we found that application of gibberellic acid and low storage temperatures of 2 °C (35.6 °F) markedly reduced the rate of degreening. However, `Oroblanco' fruit are sensitive to chilling injuries, and thus could not be stored at 2 °C for long periods. In the present study, we examined the possible application of intermittent warming (IW) and temperature conditioning (TC) treatments, in order to retain the green fruit color during long-term cold storage but without enhancing the development of chilling injuries. It was found, that following storage at 2 °C, either with or without IW and TC, the fruit retained green color up to 16 weeks, whereas at 11 °C (51.8 °F) fruit turned yellow after 8 weeks. However, untreated fruit held continuously at 2 °C developed 40, 51, and 68% chilling injuries after 8, 12, and 16 weeks, respectively. IW (storage at cycles of 3 weeks at 2 °C + 1 week at 11 °C) reduced the amount of chilling injuries to only 5, 7 and 11% after the same periods of time, respectively. TC [a pre-storage treatment for 7 days at 16 °C (60.8 °F) before continuous storage at 2 °C] effectively reduced the development of chilling injuries to only 5% after 8 weeks of storage, but was ineffective in reducing chilling damage after longer storage periods. Because chilling damaged fruit is prone to decay, the IW and TC treatments also reduced the incidence of decay development during storage. The IW and TC treatments did not affect juice total soluble solids and acid percentages, but did affect fruit taste and the amounts of off-flavor volatiles emitted from the juice. Taste panels indicated that the taste score of untreated control fruit stored at 11 °C gradually decreased during long-term storage, and that this decrease was more severe in chilling damaged fruit stored continuously at 2 °C. The taste of IW-treated fruit remained acceptable even after 16 weeks of storage, and TC-treated fruit remained acceptable for up to 12 weeks. Fruit taste scores were inversely correlated with the concentrations of ethanol and acetaldehyde detected in the juice headspace.

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Toshikazu Matsumoto, Hajime Matsuzaki, Kou Takata, Yoko Tsurunaga, Hiroyasu Takahashi, Takao Kurahashi, Shinya Maki, and Kazushi Fujiwara

of inhibition for astringency removal of 1-MCP-treated material fruit appears to differ in dried and fresh fruit. Astringency occurs as a result of acetaldehyde accumulation ( Pesis et al., 1988 ; Taira, 1996 ). On the other hand, Taira and Ono