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Aims: The effect of combinations of nisin and ethanol on the survival of Listeria monocytogenes was investigated. Methods and Results: Killing by nisin was enhanced during simultaneous exposure to ethanol (2–7% v/v). For example, while 10 IU ml−1 nisin reduced viability by 1 log unit in 20 min, a combination of this antimicrobial peptide and 5% ethanol, reduced numbers of surviving cells by 3 log units. Increasing the concentrations of either ethanol (2–7%) or nisin (10–50 IU ml−1) led to increased cell death with synergy being demonstrated for all combinations tested and at a range of temperatures from 5 to 37°C. Conclusions: Ethanol can act synergistically with nisin to reduce the survival of L. monocytogenes. Significance and Impact of the Study: Combinations of ethanol and nisin may be feasible as an effective way of controlling this pathogen in the food processing environment.

Significance and Impact of the Study: High hydrostatic pressure (HHP) is an effective nonthermal food preservation technology that can be used to increase food safety and shelf life with minimal changes in food quality. Various antimicrobial agents including bacteriocins, lysozyme, chitosan, lactoperoxidase and essential oils have been tested in combination with HHP to enhance the effect of mild-pressure treatments. This is the first report of a synergistic bactericidal effect of high pressure and acidified nitrite. A better understanding of combined preservation processes and synergistic effects will help ensure the safety of processed foods. AbstractThe bactericidal effect of acidified sodium nitrite alone or when combined with high hydrostatic pressure (HHP) treatment was examined with Escherichia coli BW25113 and Listeria monocytogenes NCTC 11994. A powerful synergistic effect of HHP plus nitrite was observed at pH 4Á0, but not at higher pH values. Escherichia coli hmpA and norV mutants lacking defences against nitrosative stress were more sensitive to pressure combined with acidified sodium nitrite than the wild-type strain, suggesting an involvement of nitric oxide in the bactericidal effect.

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