Effect of carbon dioxide on the internal lower oxygen limits of apple fruit
Christopher W. Yearsley, Nigel H. Banks and Siva Ganesh
Postharvest Biology and Technology Vol: 12 Issue: 1 Pages: 1-13
1997
บทคัดย่อ
The effect of elevated CO2 between 0 and 8 kPa on steady-state lower O2 limits based on internal atmospheres (LOLi) was estimated for postclimacteric `Cox's Orange Pippin' and `Braeburn' apples at 0 and 20°C. Two types of LOLi were estimated: the anaerobic compensation point (ACPi), and the internal fermentation threshold based either on the respiratory quotient (FTiRQ) or ethanol (EtOH) accumulation (FTiEtOH). ACPi, for both cultivars and temperatures, remained constant at 0.5 kPa O2 for `Cox's Orange Pippin' and 0.8¯1.0 O2 for `Braeburn' apples for levels of CO2 external to the fruit between 0 and 8 kPa. However, for FTiRQ and FTiEtOH, no consistent trend with level of CO2 was evident at 20°C for either cultivar. In contrast, at 0°C FTiRQ and FTiEtOH were 0.2¯0.8 kPa O2 higher at 8 kPa CO2 than at 0 kPa CO2 (with the exception of FTiRQ for `Cox's Orange Pippin'). A small decrease in O2 uptake (estimated from the difference in external and internal O2 atmospheres) was observed between 2 and 8 kPa CO2 at 20°C. Elevated CO2 slightly lowered the respiratory quotient (RQi, estimated from the ratio of differences between external and internal atmosphere partial pressures of CO2 and O2) of `Cox's Orange Pippin' in 8 kPa CO2 and `Braeburn' in 2 to 8 kPa CO2 at 20°C, and more markedly in 8 kPa CO2 at 0°C. The RQi of `Cox's Orange Pippin' and `Braeburn' apples was slightly and markedly higher respectively at 0°C compared to 20°C. The lower RQi of `Braeburn' at 20°C compared to `Cox's Orange Pippin' apples indicated `Braeburn' had a higher permeance to CO2 relative to O2 compared to `Cox's Orange Pippin'. This study indicates the tolerance of `Cox's Orange Pippin' and `Braeburn' apples to low O2 levels may be affected by levels of CO2.