Internal browning in pear fruit (Pyrus communis L. cv Conference) may be a result of a limited availability of energy and antioxidants

Storage of pears (Pyrus communis) under hypoxia, especially in the presence of increased CO2 partial pressures, can lead to development of brown core. Disorder development, concentrations of ascorbic acid (AA) and adenosine triphosphate (ATP), and respiration were examined under various O-2 (0-21 kPa) and CO2 (0 and 5 kPa) atmospheres during 31 days of storage. ATP production was estimated using the respiration data. Hypoxia increased brown core incidence, decreased AA and ATP concentrations, and lowered ATP production. AA concentrations decreased before brown core became visible. Adding CO2 to the storage atmosphere increased the severity of brown core. CO2 addition also decreased AA levels by about 46% at O-2 partial pressures of 2.5 kPa and higher. CO2, however, had variable effects on ATP production. No brown core was found in fruit kept at 0 kPa O-2 with or without CO2, nor decreased AA levels. These results support the hypothesis that brown core initiation is a consequence of membrane damage caused by a combination of oxygen free radical action and a lack of maintenance energy. This combination may lead to decompartmentation of intracellular structures and the initiation of brown pigmentation, visible in pears with disorders. (C) 2002 Elsevier Science B.V. All rights reserved