Effects of different packaging materials and methods on the physical, biochemical and sensory qualities of lettuce

In order to maintain the qualities at postharvest stages, Korean red leaf lettuces (Lactuca sativa L. cv. Tojong-mats) were packaged with different films or perforations such as perforated polypropylene with 1320 small-sized holes (PPP-1320-hole), perforated polypropylene with 4 large-sized holes (PPP-4-hole), non-perforated polypropylene (Non-PPP), non-perforated polypropylene with anti-fogging properties (Anti-Fog-PP) or without packaging (control) and stored at 10 °C up to 16 days. Minimum water loss was observed in both non-perforated films (< 3%) compared to 35% in control at the end of storage. Significant increase in CO₂ and simultaneous decline in O₂ concentration were recorded in both non-perforated films. A gradual decline in hue angle (h°) and SPAD (Soil-Plant Analyses Development) chlorophyll meter values was found in all samples during storage while the color difference (ΔE*) values showed opposite trend. However, Anti-Fog-PP treatment exhibited the least ΔE* values throughout the storage. The contents of chlorophyll a (Chl a), chlorophyll b (Chl b) and total chlorophyll (total Chl), decreased gradually in all cases with a comparatively higher declines in Non-PPP treatment on 6 days, in PPP-4-hole treatment both on 12 and 16 days. Anti-Fog-PP treatment exhibited the lowest chlorophyll degradation and least changes in anthocyanin content until the end of storage. Lettuces received scores for maintaining marketable limits up to 2, 4, 6, 12 and 16 days under control, PPP-1320-hole, PPP-4-hole, Non-PPP and Anti-Fog-PP packaging treatments, respectively. Results indicated that Anti-Fog-PP treatment could provide better postharvest qualities along with extended marketable life for about 2 weeks during storage at market display temperature.