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  • Author or Editor: George D. Nanos x
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`High-temperature controlled-atmosphere (high CO2/low O2) conditioning was investigated as a possible treatment to delay the incidence of internal breakdown of peaches and nectarines (Prunus persica L. Batsch) during subsequent cold storage. Maintaining an atmosphere of 5% to 15% CO2 added to air or to 1% to 5% O2 while conditioning peaches for 2 days at 20C partially prevented fruit ripening (compared to fruit conditioned in air), as measured by flesh softening and loss of green pigment, while no off-flavors were detected. Conditioning of peaches at 20C for 4 days in air or in air + 20% CO2 was detrimental to fruit quality, as indicated by flesh softening or detection of off-flavors.

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Storage at 0C of `O'Henry' and `Fairtime' peaches and `Red Jim' and `September Grand' nectarines (Prunus persica L. Batsch) resulted in significantly longer postharvest life than did storage at 5C, due to differences in the development of internal breakdown (IB) symptoms. Conditioning at 20C for 2 days before storage at 0 or 5C generally prolonged the storage life of fruit of these cultivars. The use of elevated CO2 during conditioning helped maintain fruit firmness. Addition of 5% CO2 to air gave the best results in maintaining fruit firmness and freedom from IB symptoms for up to 6 weeks. Reducing the O2 content kept flesh firmness high after storage but did not delay the appearance of IB. Conditioning at 30C using various atmospheres was less effective than conditioning at 20C.

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The response of pear fruits and suspension-cultured pear fruit cells to 0% or 0.25% O2 is being examined to evaluate the feasibility of using such atmospheres for postharvest insect control. These treatments inhibited ethylene production, had no effect on acetaldehyde content, and increased ethanol production in pears kept at 20C for 10 days. The blossom end area of pear fruits was more prone to anaerobiosis, as indicated by increased alcohol dehydrogenase activity and ethanol content. Pear fruit plugs showed increased respiration and ethylene production rates when skin was present compared to plugs without skin. Methods for measuring activity of alcohol dehydrogenase, pyruvate decarboxylase, and pyruvate kinase have been modified and optimized and will be used to determine changes in pear fruit tissue during low O2 treatment and subsequent recovery in air.

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Ripening of detached mature-green and black-ripe olives (Olea europaea L., cv. Conservolea) was studied during storage at 0, 5, 10, or 20 °C in air or air plus 100-200 μL·L-1 propylene. Green olive skin h° remained unchanged after 24 days at 0 or 5 °C in air or air + propylene, while olives partially lost their green color at 10 °C and developed purple color at 20 °C together with a substantial flesh softening. Propylene partially delayed flesh softening only at 10 °C. Respiration of green and black olives increased with storage temperature. Black olives had higher respiration rate than green olives. Propylene had no substantial effect on green or black olive respiration rate, except for an increase in respiration and ripening rates of green olives kept at 20 °C. Ethylene production rate of air- or air + propylene-treated green olives was almost undetectable. Black olives had higher ethylene production rate than green olives and this rate significantly increased with storage temperature. Addition of propylene had only minor effect on ethylene production of black olives. No climacteric respiratory rise or autocatalytic ethylene production was observed in green and black olives.

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