Use of Combinations of Commercially-Relevant O2 and CO2 Partial Pressures to Evaluate the Sensitivity of Nine Highbush Blueberry Cultivars to Modified Atmospheres

The physics and mechanics of atmosphere regulation in controlled atmosphere (CA) storage causes the sum of the percentages of O₂ and CO₂ in the atmosphere to equal the percentage of O₂ in the gas used to purge accumulated respiratory CO₂.  When air is used to purge accumulated CO₂, the sum of O₂ and CO₂ percentages equals 21%.  We have, therefore, tested a range of CO₂ and O₂ combinations (19/2; 18/3; 16.5/4.5; 15/6; 13.5/7.5; 12/9; 6/15; and 0/21 for CO₂/O₂, respectively, in percent) that sum to 21% on nine blueberry (Vaccinium corymbosum L.) cultivars (‘Duke’, ‘Toro’, ‘Brigitta’, ‘Ozarkblue’, ‘Nelson’, ‘Liberty’, ‘Elliott’, ‘Legacy’, and ‘Jersey’) for their effectiveness at preserving the quality of blueberry fruit stored for 8 weeks at 0 ºC.  Quality characteristics included surface mold and decay, skin reddening (associated with fruit pulp browning), fruit firmness, pulp discoloration, and ethanol and acetaldehyde content. As CO₂ increased, fruit firmness, skin reddening, and decay declined and the proportion of fruit in the higher internal quality categories tended to increase. Ethanol and acetaldehyde accumulation was minimal, indicating fermentation was not induced by the atmospheric conditions applied.  Cultivar effects were far more pronounced than atmosphere effects.  ‘Liberty’ and ‘Toro’ stored extremely well, ‘Duke’, ‘Brigitta’, and ‘Legacy’ stored well, ‘Elliott’ stored moderately well, and ‘Ozarkblue’, ‘Nelson’ and ‘Jersey’ stored poorly.