Physiological responses of Chinese pear 'Yali' fruit to CO₂-enriched and/or O₂-reduced atmospheres

Respiration and ethylene production rates of Chinese pear 'Yali' fruit (Pyrus ussuriensis Maxim. var. sinensis Kikuchi) stored in CO₂-enriched and/or O₂-reduced atmospheres. In addition, several types of polyethylene film packaging were also applied to the long-term storage of 'Yali' fruit. 1. Oxygen uptake and ethylene production in 'Yali' fruit at 20 °C decreased with increasing CO₂ concentration up to 40%. Ethylene production under 60% CO₂ was markedly inhibited, whereas O₂ uptake was promoted; a physiological disorder in the flesh developed. 2. Under the same storage condition, oxygen uptake and ethylene production consistently decreased with decreasing O₂ concentration. However, when O₂ was decreased to less than 5%, CO₂ output exceeded O₂ uptake, suggesting that anaerobic respiration was occurring. 3. Respiration was inhibited in fruit kept at 10 or 20 °C under 5% CO₂ + 3% O₂ during the first 4 days of storage and then increased suddenly thereafter accompanied by the development of a physiological disorder. 4. The storage life of the fruit packed in a film with soda lime at 10 °C, in which O₂ became to about 8%, was prolonged by about a month, as compared to that of those packed in a perforated bag. The gas concentration higher than 5% CO₂ and/or lower than 5% O₂ within a plastic bag caused an accumulation of ethanol and the development of disorder in flesh, thus shortening storage life of fruit. Our results suggest that 'Yali' fruit is sensitive to both CO₂-enriched and O₂-reduced atmospheres, and that 2% CO₂ and 8% O₂ are about optimal for its long-term storage.