ISHS Acta Horticulturae 464: International Postharvest Science Conference Postharvest 96
EFFECT OF RATE OF ESTABLISHMENT OF CA CONDITIONS ON THE DEVELOPMENT OF CO2-INJURY IN BRAMLEY'S SEEDLING APPLES |
| Authors: | D.S. Johnson, C.J. Dover, R.J. Colgan |
| Abstract:
Supplying atmospheres with partial pressures of O2 as low as 0.4 kPa in combination with up to 5 kPa CO2 has proved an effective alternative to the use of post-harvest chemical treatments, e.g. diphenylamine, for control of superficial scald in ‘Bramley's Seedling’ apples. However, the use of such 'extreme' CA conditions has occasionally caused injury to the skin and the flesh of the fruit, and the risk of injury holds back use of these techniques to replace chemical treatments. Working on the hypothesis that such injury is caused by a transient high CO2 concentration in the fruit shortly after store loading, we investigated the effect of delaying establishment of such 'extreme' CA conditions on the subsequent development of CO2-injury. ‘Bramley's Seedling’ apples were cooled at a typical commercial rate and subjected to a 20-day treatment with CO2 at 5, 10 or 20 kPa (in 1 kPa O2) established by flushing at 0, 5, 10, 15 and 20 days after loading. The incidence of external CO2-injury in fruit treated with 5, 10 and 20 kPa CO2 decreased following a 0, 5 and 10 day delay respectively and a 20-day delay resulted in less than 5% of injured fruits at the most damaging CO2 concentration (20 kPa), compared with 83% damaged fruits when flushed at day 0 (i.e. no delay). Internal CO2-injury responded in a similar way to external injury, although the flesh was generally less susceptible to injury than the skin. A 5-day delay in sealing CA containers was sufficient to prevent external and internal CO2-injury where 5 kPa CO2 (in 1 kPa O2) was established by fruit respiration as opposed to flushing, although this result was achieved in a year of low potential for CO2-injury. The incidence of external and internal injury varied according to the source of fruit. High resistance to gas diffusion was associated with increased internal injury but was not related to the extent of external injury. The application of diphenylamine prior to establishment of the most damaging treatment (20 kPa CO2 at day 0) gave complete protection against skin injury and partial protection against internal damage. | |
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