Factors affecting internal browning of new apple cultivars during storage

Longer term controlled atmosphere (CA) storage of new apple cultivars has led to more frequent observations of diffuse and radial flesh browning but understanding of factors that influence the incidence of these browning disorders is limited. Salish™ apple was used as the model cultivar for this research since it is currently commercially grown in British Columbia. Three commercial orchards were selected to bracket a range of cultural practices seen for this cultivar. Apples were harvested at four different maturities as determined using I_AD values. They were stored at 1.5 kPa O₂ + 0.5 kPa CO₂ at 0.5°C for four and seven months and then placed into 30°C, 95% RH for two weeks before assessing internal browning incidence and severity. Internal browning developed in two of the three orchards. In the most susceptible orchard, internal browning was detected in fruit harvested at the most advanced maturity after storage for four and seven months. In the intermediately affected orchard, there was a low incidence at the most advanced harvest maturity but only after seven months of storage. The disorder was clearly associated with harvest maturity. In other experiments, it was determined that delayed cooling (holding at 10°C in air for 10 days before cooling and applying CA) and ultra-low O₂ (0.7 kPa O₂ + 0.5 kPa CO₂ at 0.5°C) eliminated or significantly reduced incidence of internal browning at seven months, respectively. Internal browning can be managed by earlier harvests (based in I_AD index values) and either delayed cooling or ultra-low O₂ CA storage. The orchard effect on susceptibility may be related to relative stress levels of an orchard.