Effect of growing season, harvest maturity, waxing, low O2 and elevated CO2 on flesh browning disorders in 'Braeburn' apples

British Columbia-grown 'Braeburn' apples (Malus x domestica Borkh.) stored for 6 months in air at 0 degrees C were, on average, 70 N in flesh firmness and had 0.48% titratable acidity. Fruit held in 1.2 or 1.5% O-2 + 1.0 or 1.2% CO2 controlled atmosphere (CA) storage were 8 N firmer, 20% higher in titratable acidity, and had significantly less core browning and superficial scald than fruit held in air for the same period. However, CA-stored fruit were highly susceptible to Braeburn browning disorder (BBD) and internal cavities (IC) after cool growing seasons [1993, 1995, and 1996; < 1300 degree-days > 10 degrees C (DD10) accumulated between May 1 and harvest]. Susceptibility of fruit to BED and IC was greatest in late-harvested fruit (starch index > 2.5 on a 0-9 scale) stored in 3.0% CO2 and 1.5% O-2. Storage at 1.7, 2.0, 3.0 and 4.0 degrees C did not decrease BED or IC incidence and tended to increase core browning (1996) and flesh softening (1994 and 1996) compared with fruit kept at 0 degrees C. Coating fruit with Shellac wax, but not Carnauba wax, increased BBD in air-stored fruit. Following a cool growing season it is recommended that 'Braeburn' apples be harvested at starch index values between 2.5 and 3.0 and stored in air storage at 0 degrees C to avoid the risks of scald, BED and IC. The fruit may be stored in <1.0% CO2 (preferably close to 0.1%) and > 1.5% O-2 after warm seasons (>1300 DD10). (C) 1998 Elsevier Science B.V. All rights reserved.