Ascorbic acid and tissue browning in pears (Pyrus communis L. cvs Rocha and Conference) under controlled atmosphere conditions

The relationships between storage gas composition and ascorbic acid (AA) levels, and between AA levels and the development of internal browning, were studied in 'Conference' and 'Rocha' pears (Pyrus communis L.). In both cultivars, AA levels declined under (browning-inducing) controlled atmosphere (CA) conditions, i.e. lowered O2 and enhanced CO2 concentrations. Browning was initiated in a cultivar-dependent manner when an AA level threshold was passed. Several models describing the relation between AA levels and browning were fitted to estimate these AA thresholds. The thresholds depend on cultivar, picking date and growing location, varying between 2 and 6 mg 100 g FW-1. AA losses in both cultivars exceeded 50% of the initial values. In 'Conference' fruit, most AA was lost when fruits were transferred to CA. In 'Rocha' fruit, AA was lost mainly during long-term CA.