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  • Author or Editor: Marisela Rivera x
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Modified and controlled atmospheres with ≤ 0.5% O2 and/or ≥ 50% CO2 are insecticidal. In previous studies we have found that avocado is very sensitive and mango is very tolerant to these atmospheres. We used DSC to study the differences in response between these two fruits, and to relate that with their sensitivity/tolerance to hypoxia. Fresh or lyophilized tissues of fruits stored in air or in an insecticidal atmosphere were scanned at a temperature range of 10 to 145°C at a rate of 10°C/min. There were qualitative and quantitative differences between thermograms. There were fewer endotherms in thermograms of fresh tissue samples than in lyophilized tissue samples. Avocado thermograms showed a major endotherm at ca 15°C and 2 minor endotherms at ca 105-110°C. In addition, mango heating thermograms showed another major endotherm at ca 80°C. This endotherm was not present in the heating thermograms of avocado. and might represent a contributing factor in the tolerance of mango to insecticidal atmospheres.

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Papaya (Carica papaya L., cv. Sunrise) fruits were exposed to a continuous flow of an atmosphere containing <0.4% 02 (the balance being N2) for 0 to 5 days at 20C. Decay was a major problem, and some fruit had developed off-flavors after 3 days in low O2 plus 3 days in air at 20C. The intolerance of the fruit to low O2 correlates with an increase in the activity of pyruvate decarboxylase and lactate dehydrogenase but not with the activity of alcohol dehydrogenase. Insecticidal O2 (< 0.4%) atmospheres can be used as a quarantine insect control treatment in papaya for periods <3 days at 20C without the risk of significant fruit injury.

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