Low Oxygen Effects on Dessert Quality, Scald Prevention, and Nitrogen Metabolism of ‘d’Anjou’ Pear Fruit during Long-term Storage1

‘d’Anjou’ pears (Pyrus communis L.) harvested at optimum maturity, 6.4 kg flesh firmness, were stored in 0.5, 1.0, 1.5, 2.0, 2.5 and 5.0% O2 with CO2 concentration were maintained at 0.01 to 0.03%. Other samples were stored in commercially recommended concentrations of 2-2.5% O2 and 0.8-1.0% CO2 (i.e., regular CA), and conventional air storage. Temperatures of −1.1°C (30°F) were maintained in all cabinets throughout the 8 month storage. Oxygen concentration below 1.5% maintained the dessert quality of fruit and reduced the incidence of superficial storage scald after 8 months of storage. Fruit stored at 1.0% O2 for 8 months did not develop scald even after returning to air storage for 30 days. Oxygen concentration above 2% without CO2 had no beneficial effect on dessert quality or scald control. Regular CA storage also maintained dessert quality, but had only slight effect on scald control. Fruit stored below 2% O2 softened slower, lost titratable acids and free amino acids more slowly, and accumulated protein more slowly than samples stored at higher O2 levels for 8 months. Regular CA fruit changed similarly to those from the 1.0% and 1.5% O2 treatments. Overall fruit metabolism in 0.5% O2 was markedly retarded during the 5 to 8 month storage period.