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Edna Pesis and Rosa Marinansky

Abbreviations: AA, acetaldehyde; RQ, respiratory quotient; TSS, total soluble solids content. Supported by grant no. 1-900-85 from BARD, the U.S.-Israel Binational Agricultural Research and Development Fund. Contribution from the Agr. Res

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Yosef Al Shoffe, Abdul Sattar Shah, Jacqueline F. Nock and Christopher B. Watkins

relation to disorder incidence. At harvest and under aerobic storage conditions, apples usually have low acetaldehyde and ethanol concentrations, as well as low pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activities ( Pesis, 2005 ). Both

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F. Mencarelli, P. Savarese and M.E. Saltveit Jr.

Exposure to acetaldehyde (M) vapors that produced tissue levels of 0.02% AA (w/w) stimulated ripening of `Hayward' kiwifruit (Actinidia deliciosa L.) much more effectively than exposure to ethanol vapors that produced tissue levels of 0.18% ethanol. Tissue levels of 0.02% and 0.18% ethanol stimulated ripening, while the ripening rate of tissue with 0.04% was similar to the controls. Ethylene and CO production from M-treated tissues were, respectively, 23 times and 60% higher than from control tissues. AA induced a rapid softening that was localized in the core tissue and rendered the fruit unmarketable for 7 days after treatment.

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John C. Beaulieu and Mikal E. Saltveit Jr.

The content of acetaldehyde (AA) and ethanol (EtOH) increases in ripening climacteric fruit. Application of EtOH inhibits tomato (Lycopersicon esculentum) fruit ripening without affecting subsequent quality, and AA enhances organoleptic quality. AA inhibited ripening of mature-green tomato discs (MGTD) at about 30% conc of EtOH. The relationship between EtOH and AA inhibition of tomato fruit ripening is unclear. The inter-conversion of AA and EtOH is catalyzed by alcohol dehydrogenase (ADH) which is inhibited by 4-methylpyrazole (4-MP). No adverse physiological effects upon ripening were observed in MGTD receiving 20 μL of 4.0 mM 4-MP. Treating MGTD with 0.5 to 4.0 mM 4-MP in concert with AA (≤2.0 μL/g FW) or EtOH (≤8 μL/g FW) was not deleterious to ripening. A rapid, efficient method for the analysis of tissue AA and EtOH was linear (r2 = 0.97) for discs spiked with 0 to 45 μL EtOH. No temporal (0 to 42 h) changes in tissue AA and EtOH were detected in MGTD receiving 2.0 mM 4-MP. MGTD treated with 2.0 mM 4-MP and 8 μL/g FW EtOH had a 360-fold increase in AA after 6 days of ripening, but had no differences on EtOH conc. These conditions maximally inhibited ripening as determined by lycopene content.

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Luís Carlos Cunha Júnior, Ângelo Pedro Jacomino, Marcos José Trevisan and Gustavo Henrique de Almeida Teixeira

disruption and lead to increased levels of acetaldehyde, ethanol, ethyl acetate, and ethyl lactate, which confer undesirable aromas to the fruit ( Kader, 2003b ). In an attempt to reduce the risks caused by CAs with high levels of CO 2 , other gases have been

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John C. Beaulieu and Mikal E. Saltveit

`Castlemart' tomato (Lycopersicon esculentum Mill.) pericarp discs were used to study the physiological effects of acetaldehyde and ethanol on fruit ripening. Short-term exposure of discs from mature-green fruit to acetaldehyde vapors on a fresh mass basis (≤500 μg·g-1) or ethanol vapors (≤3 mg·g-1) promoted ripening, while higher concentrations inhibited ripening. Discs from mature-green fruit absorbed greater amounts of ethanol and produced significantly higher concentrations of acetaldehyde than discs from breaker fruit. Ripening was promoted by ethanol when the discs were unable to retain or produce a certain level of acetaldehyde. Inhibition of ripening by 4 hours of exposure to ethanol (6 mg·g-1) was almost completely abolished by hypobaric treatments (18 kPa for 24 hours). However, acetaldehyde-induced ripening inhibition (2 days exposure to 180 μg·g-1) was only slightly reduced by vacuum. Concentrations of acetaldehyde and ethanol that inhibited ripening reduced C2H4 production, whereas lower concentrations of acetaldehyde and ethanol that promoted ripening increased C2H4 production. Application of 4-methylpyrazole, an alcohol dehydrogenase inhibitor, enhanced acetaldehyde-induced ripening inhibition and reduced ethanol-induced ripening inhibition or promotion at all concentrations of acetaldehyde and ethanol tested. The inhibition or promotion of ripening of excised tomato pericarp discs by ethanol and acetaldehyde depended on initial fruit maturity, applied volatile concentration, and duration of exposure.

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Takashi Nishizawa, Satoshi Taira, Masanori Nakanishi, Masanori Ito, Masahiro Togashi and Yoshie Motomura

Acetaldehyde and ethanol production by muskmelon fruit were promoted by short-term shading of the plants for 5 days from 10 to 15 days prior to fruit maturation. Sucrose concentrations in the fruit flesh were reduced by shading, while fructose and glucose concentrations did not differ. Shading also accelerated the development of a “water-soaked” appearance in the flesh.

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B. Ratanachinakorn, A. Klieber and D.H. Simons

Tomatoes (Lycopersicon esculentum Mill. `Bermuda') were vacuum infiltrated at the breaker stage with 25 to 55 mL·L-1 ethanol (EtOH) vapor at a 10 kPa pressure for 5 minutes and then held for a further period before ripening in air at 22 °C. Fruit could tolerate these EtOH vapor concentrations for no longer than 0 to 12 hours after vacuum infiltration, depending on concentration; otherwise skin pitting, uneven ripening and off-flavors resulted. Noninjurious conditions delayed ripening, as judged by color change, by an additional 1 to 5 days compared with 4 days for the control; aroma or flavor were not altered as determined by a trained taste panel, except in extreme conditions where in some cases off-flavors increased. Soluble solids and titratable acidity did not vary, but pH increased by 0.1 units in some treatments. In control fruit EtOH was found only in the gel tissue, and acetaldehyde (AA) was higher in the gel tissue compared with the pericarp and columella, indicating different metabolic behavior of the various tomato tissues. During vacuum exposure, EtOH moved through the stem scar and to a much lesser extent through the epidermis; during subsequent exposure to EtOH more EtOH moved through the epidermis than before, but still less than through the stem scar. AA increased following EtOH uptake, but all increases in EtOH and AA disappeared before fruit ripened.

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Jianzhi Jenny Zhang and Christopher B. Watkins

The effects of postharvest treatments of air and 20 kPa CO2 (in air) at 2 or 20 °C on color, firmness, accumulations of acetaldehyde, ethanol, and ethyl acetate, activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activity, and expression of an ADH gene were studied in strawberry fruit (Fragaria ×ananassa Duch. cv. Jewel). CO2 treatment enhanced strawberry fruit firmness at 2 °C but not 20 °C, while the rate of color changes was affected by CO2 treatment at 20 °C but not at 2 °C. Temperature also affected the accumulation of acetaldehyde, ethanol and ethyl acetate in CO2-treated fruit. All three compounds accumulated in fruits at 2 °C. At 20 °C, ethanol accumulated slightly by day 6, although ethyl acetate accumulated in fruit from both atmospheres. PDC enzyme activity was higher in CO2-treated fruit than their air-treated control at 2 °C but not at 20 °C. ADH activity and ADH mRNA accumulation of the CO2-treated berries were higher than in air at 20 °C but not 2 °C. The results, overall, indicate that patterns of change among gene expression, enzyme activities, and fermentation product accumulation were not consistent.

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R.J. Bender, J.K. Brecht, E.A. Baldwin and T.M.M. Malundo

To determine the effects of fruit maturity, storage temperature, and controlled atmosphere (CA) on aroma volatiles, mature-green (MG) and tree-ripe (TR) `Tommy Atkins' mangoes (Mangifera indica L.) were stored for 21 days in air or in CA (5% O2 plus 10% or 25% CO2). The MG fruit were stored at 12 °C and the TR fruit at either 8 or 12 °C. Homogenized mesocarp tissue from fruit that had ripened for 2 days in air at 20 °C after the 21-day storage period was used for aroma volatile analysis. The TR mangoes produced much higher levels of all aroma volatiles except hexanal than did MG fruit. Both MG and TR mangoes stored in 25% CO2 tended to have lower terpene (especially p-cymene) and hexanal concentrations than did those stored in 10% CO2 and air-stored fruit. Acetaldehyde and ethanol levels tended to be higher in TR mangoes from 25% CO2 than in those from 10% CO2 or air storage, especially at 8 °C. Inhibition of volatile production by 25% CO2 was greater in MG than in TR mangoes, and at 8 °C compared to 12 °C for TR fruit. However, aroma volatile levels in TR mangoes from the 25% CO2 treatment were in all cases equal to or greater than those in MG fruit treatments. The results suggest that properly selected atmospheres, which prolong mango shelf life by slowing ripening processes, can allow TR mangoes to be stored or shipped without sacrificing their superior aroma quality.