Inactivation of Escherichia coli and Listeria monocytogenes on iceberg lettuce by dip wash treatments with organic acids.

AIMS

To study and compare the efficacy of organic acids and chlorine dipping in inactivation of Escherichia coli and Listeria monocytogenes on fresh-cut iceberg lettuce.

METHODS AND RESULTS

Fresh-cut iceberg lettuce leaves were inoculated with E. coli or L. monocytogenes. After inoculation, samples were stored at 4 degrees C for 24 h and dipped in organic acid or chlorine solutions for 2 and 5 min. E. coli and L. monocytogenes were enumerated on selective media. Treatment of fresh-cut iceberg lettuce with chlorine solution caused 1.0 and 2.0 log(10) CFU g(-1) reductions in the number of L. monocytogenes and E. coli, respectively. Maximum reduction for E. coli (about 2.0 log(10) CFU g(-1)) was obtained for samples dipped in lactic or citric acids while maximum reduction for L. monocytogenes (about 1.5 log(10) CFU g(-1)) was attained for samples dipped in lactic acid.

CONCLUSIONS

Dipping of iceberg lettuce in 0.5% citric acid or 0.5% lactic acid solution for 2 min could be as effective as chlorine for reducing microbial populations on fresh-cut iceberg lettuce.

SIGNIFICANCE AND IMPACT OF THE STUDY

Dipping in solutions containing organic acids is shown to be effective to reduce E. coli and L. monocytogenes on fresh-cut iceberg lettuce.