title: Minimal inhibitory concentrations of undissociated lactic, acetic, citric and propionic acid for Listeria monocytogenes under conditions relevant to cheese.
abstract: Minimal inhibitory concentrations (MICs) of undissociated lactic acid were determined for six different Listeria monocytogenes strains at 30 °C and in a pH range of 4.2-5.8. Small increments in pH and acid concentrations were used to accurately establish the growth/no growth limits of L. monocytogenes for these acids. The MICs of undissociated lactic acid in the pH range of 5.2-5.8 were generally higher than at pH 4.6 for the different L. monocytogenes strains. The average MIC of undissociated lactic acid was 5.0 (SD 1.5) mM in the pH range 5.2-5.6, which is relevant to Gouda cheese. Significant differences in MICs of undissociated lactic acid were found between strains of L. monocytogenes at a given pH, with a maximum observed level of 9.0 mM. Variations in MICs were mostly due to strain variation. In the pH range 5.2-5.6, the MICs of undissociated lactic acid were not significantly different at 12 °C and 30 °C. The average MICs of undissociated acetic acid, citric acid, and propionic acid were 19.0 (SD 6.5) mM, 3.8 (SD 0.9) mM, and 11.0 (SD 6.3) mM, respectively, for the six L. monocytogenes strains tested in the pH range 5.2-5.6. Variations in MICs of these organic acids for L. monocytogenes were also mostly due to strain variation. The generated data contribute to improved predictions of growth/no growth of L. monocytogenes in cheese and other foods containing these organic acids.
authors.affiliation: NIZO Food Research, Ede, The Netherlands; Wageningen University, Food Quality and Design, Wageningen, The Netherlands; Wageningen University, Laboratory of Food Microbiology, Wageningen, The Netherlands.
authors.forename: Ellen
authors.initials: E
authors.lastname: Wemmenhove
authors.affiliation: Wageningen University, Food Quality and Design, Wageningen, The Netherlands.
authors.forename: Hein J F
authors.initials: HJ
authors.lastname: van Valenberg
authors.affiliation: Wageningen University, Laboratory of Food Microbiology, Wageningen, The Netherlands.
authors.forename: Marcel H
authors.initials: MH
authors.lastname: Zwietering
authors.affiliation: Wageningen University, Food Quality and Design, Wageningen, The Netherlands.
authors.forename: Toon C M
authors.initials: TC
authors.lastname: van Hooijdonk
authors.affiliation: NIZO Food Research, Ede, The Netherlands. Electronic address: marjon.wells-bennik@nizo.com.
authors.forename: Marjon H J
authors.initials: MH
authors.lastname: Wells-Bennik
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology*; D002611:Cheese / Q000382:microbiology*; D019343:Citric Acid / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000494:pharmacology*; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000254:growth & development; D008826:Microbial Sensitivity Tests; D011422:Propionates / Q000494:pharmacology*; D013696:Temperature
chemical_list: D011422:Propionates; D019343:Citric Acid; D019344:Lactic Acid; C029658:propionic acid; D019342:Acetic Acid
keywords: Growth inhibition; Salt; Temperature; Undissociated organic acid; pH