Delayed modified atmosphere packaging of fresh-cut romaine lettuce: effects on quality maintenance and shelf-life

Fresh-cut tissues are subjected to severe injury during preparation that leads to increased respiratory activity and quality deterioration. Modified atmosphere packaging (MAP) has been used to maintain quality of fresh-cut produce, but O2 depletion and excessive CO2 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 (Lactuca sativa L.). Romaine lettuce leaves were cut, washed, dried, and placed for 0, 4, 8, and 12 hours at 5 degrees C in ambient air before packaging. Fresh-cut samples were placed into packages prepared from films having OTRs of 8.0 and 16.6 pmol.s(-1).m(-2).Pa(-1), flushed with N2 to reach an initial headspace O2 level of 1.5 kPa O2, and stored at 5 degrees C for up to 14 days. Delayed packaging affected gas composition, fermentative volatile production, off-odor development, color, CO2 injury, and tissue electrolyte leakage. With increasing delay before packaging, fermentative volatile production, off-odor development, and CO2 injury progressively decreased and discoloration increased. The modified atmospheres obtained with 16.6 OTR film increased discoloration when present, and generally had less off-odor development and CO2 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-hour delayed packaging into packages prepared from 8.0 OTR film maintained quality by inhibiting CO2 injury, off-odor development, and tissue electrolyte leakage. However, an 8-hour delayed packaging into packages prepared from 16.6 OTR film was better at maintaining the quality of fresh-cut romaine lettuce at 5 degrees C for 14 days. The results indicated that delayed packaging could be an alternative method to optimize or balance package O2 during suboptimal OTR film packaging conditions.