Responses of ‘d’Anjou’ pear (Pyrus communis L.) fruit to storage at low oxygen setpoints determined by monitoring fruit chlorophyll fluorescence

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‘d’Anjou’ pears, which are susceptible to superficial scald (scald), were stored in air or controlled atmospheres containing 1.5kPa O2 or a minimal partial pressure determined using real-time monitoring of fruit chlorophyll fluorescence. In two experiments, the low O2 setpoints were 0.4 and 0.5kPa. During experiment 1, pears stored continuously at the low O2 setpoint did not develop scald while scald developed on fruit stored in air, 1.5kPa O2, or 0.5kPa O2 for 6 months then 2 months at 1.5kPa O2. Fruit from 2 of 3 lots stored in 0.5kPa O2 during year one of the two year study developed peel black speck, a disorder previously reported on d’Anjou fruit stored in pO2 of 1kPa or below. All CA environments slowed peel color change with the low pO2 having a larger effect on color after longer storage durations. Fruit softening was also reduced by the low pO2 compared with fruit stored in air or 1.5kPa O2. Fruit stored in 0.4kPa O2 with 0.1kPa CO2 in experiment 2 did not soften to a commercially acceptable value during the shelf life period after removal from storage. The results indicate low O2 partial pressure set points established by monitoring fruit chlorophyll fluorescence can prevent ‘d’Anjou’ scald but may result in black speck development as well as insufficient softening during a typical shelf-life period.