An antimicrobial effect of benzoic acid (BA) and ethylenediaminetetraacetic acid (EDTA) was evaluated as a potential antimicrobial treatment against Escherichia coli O157:H7 and Listeria innocua. A 30 min exposure to the combination of 15 mM BA and 1 mM EDTA at 22 °C resulted in approximately 3 logarithmic reductions in stationary phase E. coli O157:H7. Logarithmic phase E. coli O157:H7 was more sensitive (P < 0.05) to the treatment and 1 mM EDTA alone caused more than 5 logarithmic reductions. L. innocua was also sensitive to a treatment with 15 mM BA alone, which induced 5 logarithmic reductions. By increasing the temperature of the solution containing 15 mM BA and 1 mM EDTA to 40 °C, more than 5 logarithmic reductions in stationary phase E. coli O157:H7 was observed after 5 min of treatment. However, the antimicrobial effect was attenuated (reaching less than 1 logarithmic reductions) at 4 °C. In addition, the combined BA and EDTA treatment retained its antimicrobial effect against E. coli O157:H7 for at least 6 cycles of treatment over 6 days at room temperature (22 °C). In a simulated spinach washing study, 15 mM BA and 1 mM EDTA together were able to prevent cross-contamination of E. coli O157:H7. The results highlight the potential use of combination of BA (15 mM) and EDTA (1 mM) to address microbial risk from E. coli O157:H7 and L. innocua in fresh produce industry.
Practical application: This study demonstrates the effectiveness of benzoic acid (BA) and EDTA mixture in inactivating bacteria in the water used for produce washing and reducing the incidence of cross-contamination during washing of fresh produce. Use of BA + EDTA mixture has significant benefits such as: (a) ability to be reused, (b) effectiveness in the presence of organic matter, and (c) reduced need of monitoring wash water conditions such as pH, concentration and organic matter.
Keywords: Escherichia coli; Listeria; antibacterial activity; benzoic acid; produce safety.
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