Microbial quality of fresh-cut iceberg lettuce washed in warm or cold water and irradiated in a modified atmosphere package

摘要

The microbial keeping quality of fresh-cut iceberg lettuce was determined after being washed in either cold water (5C) for 3 min or warm water (47C) for 2 min followed by a cold water rinse (5C) and packaged in a modified atmosphere film bag. The lettuce samples were treated with gamma radiation to 0, 1 or 2 kGy while maintaining a refrigerated temperature (4C). The samples were analyzed for total aerobic, total coliform and Enterobacteriaceae counts after refrigerated storage up to 12 days. No difference in aerobic counts was observed between the hot- and cold-washed samples immediately after washing. The coliform and Enterobacteriaceae counts were reduced by 2 log after the warm water wash and no difference for the cold water-washed sample. The irradiation treatment at 1 kGy reduced the aerobic, coliform and Enterobacteriaceae counts by 2 log for the warm-washed samples. At the 2-kGy treatment level, the aerobic and coliform counts were reduced by 3 log for the cold-washed lettuce, whereas the Enterobacteriaceae counts were reduced by only 2 log. The observed log reductions in bacterial counts after irradiation were maintained for 12 days when stored at 4C. The combination of a cold water wash and irradiation to 2 kGy had the best microbial keeping quality.