Internal browning in Pink Lady apples is a complex disorder that is influenced by both pre and postharvest factors.

The term “internal browning” refers to a group of separate disorders that have different (though sometimes overlapping) causes and management strategies. The two main disorders are “radial” and “diffuse” flesh browning.

Both the radial and diffuse types of the disorder can be seasonal in nature, with wide variability in the incidence and severity between both growing locations and seasons.

The main seasonal risk predictor is the accumulation of growing degree days (GDD) between full bloom and harvest.

The radial type develops in growing regions that accumulate more than 1100 GDD, with the risk decreasing the higher the accumulation of GDD above 1100.

The diffuse type develops in growing regions that accumulate less than 1100 GDD, with the risk increasing the lower the accumulation of GDD below 1100.

Pink Lady Apples Growing Degree Days 2018-2024 Mid March

Source: AgroFresh Australia, 2024

In 2024, the accumulation of GDD is looking favourable for most regions having a relatively reduced risk of the fruit being susceptible to developing internal browning. This is particularly the case when compared to recent years where the risk was higher, as seen in the seasonal accumulation in GDD.

There are still a few weeks of GDD accumulation to go before the 2024 Pink Lady harvest so the seasonal risk is still to be determined and may change from current projections.

While the seasonal climate can establish the risk of the development of the disorder, postharvest factors can manage the development of the disorder to either the minimum or the maximum potential.

There is no “silver bullet” for the management of internal browning in Pink Lady apples. All pre and postharvest factors need to be managed to the best of your ability in order to reduce the risk as much as possible.

Maturity and storage guidelines for optimal management of Pink Lady apples to reduce the development of internal browning:

  • Harvest Maturity:

    • SPI of 2-3.5 (1-6 scale)
    • Firmness of > 8.0 kgf
    • Brix of >14
  • Cooling:

    • Stepwise cool
    • Typical stepwise cooling procedure:

      Load room at 5°C, reduce by 0.5-1°C per week to destination of 1-2°C (higher if risk of diffuse browning)

  • Controlled Atmosphere:

    • Standard atmosphere for long term storage is 2% O2, <1% CO2
    • Critical to maintain CO2 as low as possible during first 8 weeks of storage by venting, using CO2 scrubbers or lime
    • It is common to delay establishment of CA until destination temperature is achieved


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