Carbon Dioxide Injury and Market Quality of Lettuce Held in Controlled Atmospheres1

Abstract

Abstract Storage atmospheres with 2-1/2, 5 or 10% CO 2 caused a physiological injury to lettuce almost identical to the brown stain observed in lettuce from rail cars and trailers in which CO 2 concentrations exceeded 2% at destination. Carbon dioxide injury, or brown stain, was not always evident when lettuce was removed from the controlled atmosphere, after 7 days at 38°F, but became more evident during a subsequent 4 days at 50° in air. About 16% of the heads held at 2–1/2% CO 2 developed brown stain while 38% and 86% of the heads developed the disorder in lots held at 5% and 10% CO 2 , respectively. Significantly more heads developed brown stain when the CO 2 was combined with 3% oxygen than when combined with 21% Ο 2 Decay, pink rib, and tipburn were not significantly influenced by the O 2 or CO 2 level. Increased levels of CO 2 reduced the severity of butt discoloration in lettuce examined immediately after storage in the controlled atmosphere, but after an additional 4 days at 50°F in air, the differences were not evident. The danger of physiological injury from 2-1/2 to 10% CO 2 during storage or shipping outweighs the small improvement in butt color and general appearance.