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

'd'Anjou' pears, which are susceptible to superficial scald (scald), were stored in air or controlled atmospheres containing 1.5 kPa 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 0.5 kPa. During experiment 1, pears stored continuously at the low O2 setpoint did not develop scald while scald developed on fruit stored in air, 1.5 kPa O2, or 0.5 kPa O2 for 6 months then 2 months at 1.5 kPa O2. Fruit from 2 of 3 lots stored in 0.5 kPa 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 1 kPa 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 1.5 kPa O2. Fruit stored in 0.4 kPa O2 with 0.1 kPa 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.

Research highlights▶ 'd'Anjou pears stored at 0.5 kPa or less oxygen during controlled atmosphere storage did not develop superficial scald. ▶ Responses to the low O2 CA for quality and disorders other than superficial scald varied with orchard lot. ▶ Fruit chlorophyll fluorescence did not change during development of peel black speck.