Reducing CO2 accumulation and its phytotoxicity to lettuce with absorbent in hermetic storage as a simulation of long-term fumigation

Authors: Liu, Samuel; Liu, Yong Biao

Submitted to: Journal of Asia-Pacific Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2014
Publication Date: 5/1/2014
Citation: Liu, S.S., Liu, Y. 2014. Reducing CO2 accumulation and its phytotoxicity to lettuce with absorbent in hermetic storage as a simulation of long-term fumigation. Journal of Asia-Pacific Entomology. 17:435-439.

Interpretive Summary: Low temperature phosphine fumigation has been found to cause injuries to lettuce when treatment time is long, but the injuries can be prevented with CO2 and ethylene absorbents. In this study, romaine and iceberg lettuce were hermetically sealed in fumigation chambers for 3 days to simulate phosphine fumigation with and without CO2 and ethylene absorbents. The study showed that injuries to lettuce were caused by an accumulation of CO2. In the absence of the absorbents, CO2 levels in fumigation chambers increased steadily to over 3% by the end of 3-day storage. Injuries to lettuce were consistent with CO2 injuries. No ethylene was detected and no ethylene specific injury was found. The hermetic storage with the absorbents, however, resulted in no increase in lettuce injury and no reduction in lettuce quality as compared with controls. Therefore, CO2 absorbent was effective in preventing the injury to lettuce. The results from the current study not only provided a practical method to prevent injury to lettuce associated with phosphine fumigation, but also pointed a new direction for future research efforts to develop safe and effective phosphine fumigation treatments for postharvest pest control on fresh commodities.

Technical Abstract: Iceberg and romaine lettuce were subjected to hermetic storage as a simulation of long-term fumigation without a fumigant to determine: 1) effects of long hermetic storage on atmosphere composition and postharvest quality of lettuce, and 2) whether the negative effects can be prevented by scrubbing plant volatiles with absorbents. Commercial lettuce was hermetically sealed in fumigation chambers with or without CO2 and ethylene absorbents for 3 d at 2ºC. CO2 and ethylene levels were monitored over time, and lettuce quality was evaluated 14 d post-treatment. In the absence of absorbents, CO2 level increased steadily from 0.08% at the start to 3.36% at the end of the 3 d hermetic storage. There was no detectable accumulation of ethylene as monitored with detection tubes at the detection limit of 0.1ppm. Hermetic storage resulted in extensive injuries to iceberg and romaine lettuce, and quality degradation as compared with the controls that were not in hermetic storage. The injuries were predominantly in the form of brown stains caused by CO2. Ethylene did not appear to be an important factor associated with lettuce injury in this study. In the presence of absorbents, CO2 level remained low throughout the storage and ethylene was undetectable. Lettuce quality scores were either the same or better than lettuce in the control. Injury and reduced quality of hermetically stored lettuce was mainly caused by CO2 accumulation, not by ethylene. Our findings suggest that CO2 absorbent has the potential to prevent injury to lettuce in low temperature fumigation treatments, especially when treatment time is long.