Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 21, 2004
Publication Date: December 31, 2004
Citation: Kim, J., Luo, Y., Saftner, R.A., Gross, K.C. 2005. Effect of delayed packaging and modified atmosphere packaging on quality of fresh-cut romaine lettuce. Journal of the American Society for Horticultural Science. 130:116-123. Interpretive Summary: Packaged fresh-cut vegetables are becoming more and more popular because they are convenient and ready-to-eat. The quality of packaged fresh-cut lettuce and other salad vegetables is best maintained by selecting packaging films that match the oxygen movement through the film to the respiration rate of the product being packaged. This practice faces several challenges among which is the large variation in respiration rates from one lot of lettuce to another, and the difficulty of changing films in a commercial practice quickly enough to correct for changing respiration rates of the produce being packaged. In this study, we found that delaying the packaging of fresh-cut romaine lettuce for up to 12 hours after fresh-cut processing is an effective alternative to continually changing packaging films to maintain the quality of the lettuce being packaged. These findings provide the fresh-cut industry with a practical method for maintaining the quality of packaged fresh-cut lettuce in situations where the packaging film is sub-optimal and the quality of the fresh-cut product would otherwise be compromised.
Technical Abstract: Fresh-cut tissues are subjected to severe injury during preparation that leads to increased respiratory activity and quality deterioration. Modified atmosphere packaging (MAP) with 2 to 5 kPa oxygen and 8 to 12 kPa carbon dioxide has been used to maintain quality of fresh-cut produce, but oxygen depletion and excessive carbon dioxide accumulation can be injurious. This study was conducted to evaluate the effect of delayed packaging and MAP using two different oxygen transmission rate (OTR) films on quality maintenance and shelf stability of fresh-cut romaine lettuce. Romaine lettuce leaves were cut, washed, dried, and placed for 0, 4, 8, and 12 h at 5 C in ambient air before packaging. Fresh-cut samples were packaged into bags prepared from films having OTRs of 8.0 and 16.6 pmol/sec/square meter/Pa, flushed with nitrogen to reach an initial headspace oxygen level of 1.5 kPa oxgyen, and stored at 5 C for up to 14 days. Delayed packaging affected gas composition, fermentative volatile production, off-odor development, color, and carbon dioxide injury. With increasing delay before packaging, fermentative volatile production, off-odor development, and carbon dioxide injury progressively decreased and discoloration increased. Modified atmosphere packaging with 16.6 OTR film increased discoloration and inhibited off-odor development and carbon dioxide injury compared to MAP with 8.0 OTR film. Delayed packaging affected overall quality of fresh-cut romaine lettuce packaged with both films. A 12-h delayed packaging into bags prepared from 8.0 OTR film maintained quality by inhibiting carbon dioxide injury and off-odor development. However, an 8-h delayed packaging into bags prepared from 16.6 OTR film was better at maintaining the quality of fresh-cut romaine lettuce at 5 C for 14 days. The results indicated that delayed packaging and MAP could maintain the quality and shelf stability of fresh-cut romaine lettuce better than MAP treatment alone.