Influence of Washing Method on the Quality of Prepacked Iceberg Lettuce

The contamination of minimally processed fresh products such as fresh-cut Iceberg lettuce with microorganisms especially Escherichia coli and Salmonella spp. is a serious safety problem in the fresh food business. Therefore, the elimination of such microorganisms on sliced Iceberg lettuce by washing with water, ozonated water (1.5 ppm ozone concentration) and combinations of both was investigated. After washing and after six days of storage at 4°C the quality of the lettuce slices was determined by sensory evaluation, microbiological analysis, and cell sap pH, Vitamin Cand sugar content measurements. Washing lettuce slices with tap water, ozonated water, ozonated water followed by tap water always resulted in a decrease in microbial populations of one log unit per 500 gram sample. Washing with water followed by washing with ozonated water resulted in a half log reduction of cfu. After storage a three log higher growth of the microorganisms in the water-washed samples was observed compared to the treatment with tap water followed by washing with ozonated water. The Vitamin C and sugar contents were not affected by ozonated water. The application of ozone is helpful for lettuce sanitation and harmless for the contents of lettuce.