Carbon Dioxide-enriched Atmospheres During Cold Storage Limit Losses from Botrytis but Accelerate Rachis Browning of 'Redglobe' Table Grapes
We evaluated a range of CO2 and O2 concentrations as a potential substitute to SO2 treatments for controlling decay development on ‘Redglobe’ table grape during storage. During the 1998 season, early (14% soluble solids concentration, SSC) and late harvested (17% SSC) ‘Redglobe’ grapes were stored in 16 controlled atmospheres of 5, 10, 15, 20, and 25 kPa CO2 combined with 3, 6, and 12 kPa O2. During the 1999 season, 10 or 15 kPa CO2 combined with 3, 6, and 12 kPa O2 were tested in comparison with air stored grapes as control. In the 2000 season, late harvested ‘Redglobe’ grapes were kept in 12 kPa CO2+6 kPa O2 in comparison with standard commercial storage practices of SO2 fumigation. None of the atmospheres tested for up to 12 weeks at 0 °C influenced SSC, titratable acidity (TA), SSC:TA, or berry shatter and browning. Rachis browning was accelerated and trained judges perceived ‘off-flavor’ in grapes exposed to CO2 levels above 10 and 15 kPa for early and late harvested ‘Redglobe’ grapes, respectively. Atmospheres including above 10 kPa CO2 controlled decay incidence and spread among berries (nesting) independent of O2 concentrations during storage at 1 °C for up to 8 weeks and after 3 days at 20 °C, simulating a retail display period. Based on these data, a combination of 10 kPa CO2 with 3, 6 or 12 kPa O2 is suggested for up to 12 weeks storage for late harvested ‘Redglobe’ grapes. An atmosphere of 10 kPa CO2+6 kPa O2 is suggested for early harvested ‘Redglobe’ grapes, but not to exceed 4 weeks.