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Edna Pesis and Rosa Marinansky

Application of acetaldehyde (AA) at 90 to 360 mm to intact grape berries (Vitis vinifera L. cv. Sultanina and Vitis vinifera L. cv. 103) caused an increase in CO2 production rate and a reduction in ethylene evolution rate. The increase in CO2 production rate was accompanied by a decrease in juice acidity without any change in the total soluble solids content. Addition of ACC to berry halves dramatically increased ethylene production, which was inhibited by AA. Ethanol, applied at the same concentrations as AA, neither caused a reduction in ethylene evolution nor inhibited the conversion of ACC to ethylene. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

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Edna Pesis, Rosa Marinansky, Giora Zauberman and Yoram Fuchs

Prestorage treatment of avocado fruit (Persea americana Mill. cv. Fuerte) with a low-O2 atmosphere (3% O2 + 97% N2) for 24 hours at 17C, significantly reduced chilling injury (CI) symptoms after storage at 2C for 3 weeks. Fruit softening was also delayed by this treatment. The treated fruit had lower respiration and ethylene production rates during storage at 2C and subsequently at 17C. Electrolyte leakage was significantly lower in peel disks from treated fruit. Reducing power, expressed as total sulfhydryl groups, was higher in the peel and pulp of low-O2-treated fruit. The amount of peel chlorophyll was inversely correlated with the severity of CI symptoms.

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Edna Pesis, Rosa Ben Arie, Oleg Feygenberg and Fanny Villamizar

Bananas have a short shelf life after ethylene treatment and there is a high commercial demand to increase the storage life of individual clusters at the retail stage. To extend the shelf life of ethylene-pretreated banana, two different forms of modified atmosphere packaging (MAP) were used. In the first, individual clusters of ethylene-pretreated bananas were stored in a range of microperforated polyethylene (PE) bags (25 μm) creating various MAPs. Storage in PE bags with low microperforation (PE8) that created an atmosphere with 11% CO2 and 12% O2 was the most effective treatment for delaying banana ripening. The banana clusters kept firmer with nice peel color after 1 week at 20 °C, but the humidity inside the bags caused some decay development on the crown cut. In the second type of MAP individual clusters of ethylene-pretreated bananas were stored in air-evacuated PE bags (80 μm) under light vacuum (550 mm Hg) for short periods of 24 to 48 hours followed by storage in the same PE bags after releasing the vacuum. Storing bananas in air-evacuated bags for 24 to 48 hours reduced O2 levels to 1% and increased the production of CO2 up to 30%, but perforating the bags dramatically reduced the CO2 level to around 9% and increased the O2 level to 12%. Storing ethylene-pretreated banana clusters under vacuum for a limited time (24 to 48 hours), did not cause any damage, although the levels of acetaldehyde (AA) and ethanol increased dramatically. The AA and ethanol levels of 150 and 300 μL·L–1, respectively, that accumulated in the PE bags did not cause any off-flavors; on the contrary, the taste panelists preferred these bananas. Adding ethylene absorbents (EAs) to the air-evacuated PE bags reduced the ethylene levels as well as the AA and ethanol levels in the bags, which indicate that EAs also absorbed the AA and ethanol volatiles. Storing ethylene-pretreated banana clusters under vacuum for 24 to 48 hours was the most effective treatment for delaying ripening and senescence in yellow bananas (stage 3 to 4).

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John C. Beaulieu, Edna Pesis and Mikal E. Saltveit

An in vitro assay was used to determine the effect of AA and pH on the enzymatic and nonenzymatic production of ethylene (C2H4) from ACC. We were interested in the effect of AA on C2H4 production from ACC because aldehydes, primarily AA, can accumulate in tissue as the result of ripening, storage under modified atmospheres, packaging, and stress. Using crude extracts of ACC oxidase from tomato (Lycopersicon esculentum Mill. `Castlemart') and apple (Malus ×domestica Borkh. `Golden delicious'), C2H4 production from ACC was shown to increase in response to an increase in pH above 7.2 and inclusion of 0.2 to 2 mm AA. Nonenzymatic C2H4 production from ACC also increased linearly with increasing AA concentrations in all the buffers tested. Removal of ascorbate or O2 suppressed AA-induced nonenzymatic C2H4 production. Nonenzymatic AA-induced production of C2H4 from ACC appeared to be an ascorbate dependent oxidation, which was augmented by O2 and was sensitive to minor pH fluctuation. The nonenzymatic AA-stimulated conversion of AEC to 1-butene lacked stereospecificity. Formaldehyde and propionaldehyde also stimulated C2H4 production from ACC. These data indicate that ACC oxidase assays or C2H4 measurements assessing physiological status can be seriously affected by the presence of aldehydes, such as AA. Chemical names used: AA, acetaldehyde; ACC, 1-aminocyclopropane-1-carboxylic acid; AEC, 1-amino-2-ethylcyclopropanecarboxylic acid; ADH, alcohol dehydrogenase; EtOH, ethanol.