Effects of vegetable type and antimicrobial dipping on survival and growth of Listeria innocua and E. coli


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Summary The survival and growth of inoculated strains of Listeria innocua and Escherichia coli during storage on ready-to-use vegetables (lettuce, dry coleslaw mix) were examined. The effects of antimicrobial dipping treatments (100 ppm chlorine solution, 5 min, 1% citric acid solution, 5 min, 1% ascorbic acid, 5 min) on inoculated samples were also investigated. Populations of L. innocua and E. coli on undipped lettuce significantly increased (P < 0.05, by 1–1.5 log cycles), while populations on undipped coleslaw gradually decreased (P < 0.05) during a 14-day storage period at 8 °C. The efficacy of the disinfection treatments were dependent on vegetable type and its microbial load; they were more effective on lettuce than on coleslaw. In general, antimicrobial dipping of lettuce or coleslaw significantly reduced (P < 0.05) initial L. innocua, E. coli and total mesophilic populations but resulted in enhanced survival and/or growth during extended storage at 8 °C.