Delayed CA and oxygen at 1 kPa or less control superficial scald without CO2 injury on Bramley's Seedling apples

Controlled atmosphere (CA) storage experiments were carried out on Bramley' s Seedling (Bramley) apples (Malus domestica Borkh.) over 2 years to determ ine the extent to which CO2 injury could be ameliorated by delayed establis hment of a storage atmosphere that deters scald, and the potential for redu cing store O-2 concentration below 1 kPa to compensate for loss of scald co ntrol through delayed atmosphere establishment. Bramley apples from 15 comm ercial orchards did not develop external or internal CO2 injury when the se aling of CA containers was delayed by 10 days from loading (5 days from the completion of cooling to 4 degrees C). CA conditions of 5 kPa CO2 and 1 kP a O-2 (5/1) were established subsequently by fruit respiration. Longer dela ys were required where conditions were established by flushing with N-2 and CO2 immediately after sealing. Some internal injury (brownheart) occurred after establishment of CA conditions by flushing, despite a 15 day delay. S cald was controlled less effectively when establishment of 5/1 conditions w as delayed, particularly if these were achieved by fruit respiration rather than by flushing. A progressive reduction in scald was achieved by maintai ning O-2 concentrations at 0.8, 0.6 or 0.4 kPa, in the presence of 5 kPa CO 2. Although products of anaerobic respiration increased progressively at lo wer oxygen concentrations, these remained below suggested of factory thresh olds. A strategy was devised for CA establishment and storage conditions th at prevent CO2 injury and extend the scald-free period of apples not treate d with a chemical antioxidant prior to storage. (C) 1999 Elsevier Science B .V. All rights reserved.