INFLUENCE OF PACKAGING TREATMENTS ON THE KEEPING QUALITY OF SALINAS LETTUCE

Heads of lettuce (Lactuca sativa L., cv. 'Salinas') were individually wrapped or sealed in nonoriented perforated (22 mu m thickness) or unp erforated (25 or 50 mu m thickness) nerv polypropylene (PP) films, and stored for 2 weeks at 2 degrees C plus 2.5 d at 12 degrees C. Vacuum cooling and/or active modification of the atmosphere within the packag e by flushing a gas mixture were applied. Quality of lettuce by scorin g wilting, physiological disorders, bacterial decay and overall visual quality was determined. In naked heads stored in air and by lettuce w rapped in perforated PP, russet spotting and pink rib, the main disord ers of lettuce during postharvest, developed. However, in all treatmen ts with sealed PP bags, these disorders practically did not appear Hea rt leaf injury and brown stain developed on lettuce sealed in PP bags, particularly after transfer to higher temperature. Pink rib and heart leaf injury mainly appeared in vacuum cooled lettuce. The reason for this susceptibility that has not been previously reported, is unknown and additional research is needed to identify the factors involved Low O-2 was related with high quality score. The best results were obtain ed in vacuum cooled lettuce packed in PP bag with initial 21.6 g/L O-2 and O g/L CO2 atmosphere. (C) 1996 Academic Press Limited