Effect of pH on the inhibition of Listeria spp. by vanillin and vanillic acid.
The antimicrobial effects of vanillin and vanillic acid were verified against several species and strains of Listeria monocytogenes, Listeria innocua, Listeria grayi, and Listeria seeligeri in a laboratory medium adjusted to pH values ranging from 5.0 to 8.0. Medium pH had little influence on the MIC of vanillin as determined by a broth dilution assay, and growth of all test strains was inhibited by concentrations ranging from 23 to 33 mM. In contrast, none of the strains were inhibited by 100 mM vanillic acid at pH > 6.0, but complete inhibition was achieved at pH 5.0 with 10 mM. The effect of pH was further characterized by incubation of L. monocytogenes, L. innocua, and L. grayi in media containing 30 mM vanillin or 60 mM vanillic acid at pH 5.0, 6.0, and 7.0. Bactericidal effects increased with pH in media supplemented with vanillin. An inverse relationship was found for vanillic acid, and the lethality of the compound increased with declining pH. Mixtures of vanillin and vanillic acid exhibited additive inhibitory effects, particularly at lower pH. These natural antimicrobial compounds could prove useful either alone or in mixtures for the control of Listeria spp. in food products.
Delaquis
Pascal
P
Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, 4200 Highway 97 South, Summerland, British Columbia, Canada V0H 1Z0. delaquisp@agr.gc.ca
Stanich
Kareen
K
Toivonen
Peter
P
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001547:Benzaldehydes / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004305:Dose-Response Relationship, Drug; D005421:Flavoring Agents; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods; D006863:Hydrogen-Ion Concentration; D008087:Listeria / Q000187:drug effects / Q000254:growth & development*; D008089:Listeria monocytogenes / Q000187:drug effects / Q000254:growth & development; D008826:Microbial Sensitivity Tests; D014641:Vanillic Acid / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D001547:Benzaldehydes; D005421:Flavoring Agents; C100058:vanillin; D014641:Vanillic Acid