Pithy brown core in 'd'Anjou' pear (Pyrus communis L.) fruit developing during controlled atmosphere storage at pO2 determined by monitoring chlorophyll fluorescence

Physiological responses and fruit quality of 'd'Anjou' pear fruit from five orchard lots were evaluated after cold storage in air or controlled atmospheres (CA) with the O2 concentration based on assessment of fruit chlorophyll fluorescence (CF) or standard conditions (1.5 kPa O2). The pCO2 for all CA fruit was 0.5 kPa. Softening, acid loss, and peel degreening of all lots were delayed at one or more evaluation dates (2, 4, 6, 8 months) by previous storage at the CF pO2 compared with fruit stored in 1.5 kPa O2 or in air. Superficial scald developed on fruit previously stored in air but not on fruit stored in a CA. Pithy brown core developed on fruit from all lots stored at the CF pO2 and on fruit stored at 1.5 kPa in 3 of the 5 lots. Pithy brown core incidence decreased with advanced harvest maturity. Post-storage ethylene and CO2 production were in most instances lowest for fruit stored at the CF pO2. A significant relationship between fruit ethanol content and pithy brown core incidence was observed. Results indicate low pO2 storage based on CF monitoring slows fruit ripening relative to fruit stored at 1.5 kPa O2, prevents superficial scald development compared with fruit stored in air, however, development of pithy brown core in fruit stored at the CF pO2 was not accompanied by a change in CF.