Abstract
The first goal of this study was to determine the packaging film O 2 permeability required to maintain a steady-state O 2 concentration of 3% in modified-atmosphere packaging (MAP) of minimally processed romaine lettuce ( Lactuca sativa L.). The second goal of the study was to determine the extent to which MAP could preserve lettuce quality and consequently extend product shelf life. Oxygen consumption rates of commercially prepared lettuce samples were determined in a closed system for each of three atmospheres (3% O 2 combined with either 6%, 10%, or 14% CO 2 ). Enzymatic, quadratic, and linear mathematical models were compared to determine which best described the respiratory data. The linear model was the most suitable and was used to predict the O 2 consumption rate of the minimally processed romaine lettuce under the desired package headspace gas concentrations. The predicted O 2 consumption rate was used to calculate the necessary O 2 permeability for the packaging film. Packages (21.6 × 25.4 cm) were constructed from a polypropylene-polyethylene-laminate film with the appropriate O 2 permeability. Packaged samples were stored under three modified atmospheres (MAs) (3% O 2 combined with either 6%, 10%, or 14% CO 2 ) for 20 days, and headspace gas concentrations, lettuce appearance, and color were evaluated every other day. Growth of pectinolytic and lactic acid bacteria was also studied. The O 2 consumption rate of the lettuce decreased with increasing CO 2 levels. The O 2 levels in the MA packages equilibrated at 7% to 11%. Compared to a control atmosphere of air, MAP delayed the development of tissue discoloration. Preliminary results indicated no effect of MAP on microbial growth. Of the three CO 2 levels, 10% was slightly more effective than 6% and 14%. Critical choice of packaging permeabilities combined with MAP maintained the quality of minimally processed romaine lettuce and thereby increased shelf life by about 50%.
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Claims 8
Claim · model-written summary
The linear model best described lettuce respiratory data.
- Taxon
- romaine lettuce
Lactuca sativa var. longifoliae0 - Outcome
- O 2 consumption ratee0
- Direction
- most suitablee0
Not reportedComparatorValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The linear model was the most suitable and was used to predict the O 2 consumption rate of the minimally processed romaine lettuce”
Claim · model-written summary
Lettuce oxygen consumption decreased as carbon dioxide increased.
- Taxon
- lettuce
Lactuca sativae0 - Outcome
- O 2 consumption ratee0
- Direction
- decreasede0
- Setting
- increasing CO 2 levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The O 2 consumption rate of the lettuce decreased with increasing CO 2 levels.”
Claim · model-written summary
Packaged oxygen levels equilibrated at 7% to 11%.
Not reportedTaxon
Verbatim
e0“The O 2 levels in the MA packages equilibrated at 7% to 11%.”
Claim · model-written summary
Modified atmosphere packaging delayed tissue discoloration compared with air.
Not reportedTaxon
Verbatim
e0“Compared to a control atmosphere of air, MAP delayed the development of tissue discoloration.”
Claim · model-written summary
Preliminary results found no effect of modified atmosphere packaging on microbial growth.
Not reportedTaxonComparator
Verbatim
e0“Preliminary results indicated no effect of MAP on microbial growth.”
Claim · model-written summary
The 10% carbon dioxide atmosphere was slightly more effective than 6% or 14%.
- Treatment
- 10%e0
- Outcome
- slightly more effectivee0
- Direction
- slightly more effectivee0
- Comparator
- 6% and 14%e0
Not reportedTaxon
Verbatim
e0“Of the three CO 2 levels, 10% was slightly more effective than 6% and 14%.”
Claim · model-written summary
Selected packaging permeability with modified atmosphere packaging maintained lettuce quality.
- Taxon
- romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- packaging permeabilities combined with MAPe0
- Outcome
- qualitye0
- Direction
- maintainede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Critical choice of packaging permeabilities combined with MAP maintained the quality of minimally processed romaine lettuce and thereby increased shelf life by about 50%.”
Claim · model-written summary
Selected packaging permeability with modified atmosphere packaging increased lettuce shelf life by about 50%.
- Taxon
- romaine lettuceLactuca sativa var. longifoliae0
- Treatment
- packaging permeabilities combined with MAPe0
- Outcome
- shelf lifee0
- Direction
- increasede0
- Value
- about 50%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Critical choice of packaging permeabilities combined with MAP maintained the quality of minimally processed romaine lettuce and thereby increased shelf life by about 50%.”
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See all 17 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.