Open AccessDesign and Analysis of a Modified-atmosphere Package for Minimally Processed Romaine Lettuce
Author(s) -
Kevin Segall,
Martin G. Scanlon
Publication year - 1996
Publication title -
journal of the american society for horticultural science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.408
H-Index - 80
eISSN - 2327-9788
pISSN - 0003-1062
DOI - 10.21273/jashs.121.4.722
Subject(s) - lactuca , modified atmosphere , shelf life , polyethylene , polypropylene , food packaging , chemistry , carbon dioxide , permeability (electromagnetism) , food science , horticulture , materials science , mathematics , composite material , biology , membrane , biochemistry , organic chemistry
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%.