title: Reduction of Listeria monocytogenes on frankfurters treated with lactic acid solutions of various temperatures.
abstract: United States regulations require ready-to-eat meat and poultry processors to control Listeria monocytogenes using interventions which may include antimicrobials that reduce post-processing contamination by at least 1 log-cycle; if the treatment achieves > or = 2 log reductions, the plant is subject to less frequent microbial testing. Lactic acid (LA) may be useful as a post-lethality intervention and its antimicrobial properties may increase with temperature of application. The aim of this study was to evaluate the effect of LA solution concentration and temperature on L. monocytogenes counts of inoculated frankfurters and to identify parameters (concentration, temperature, and time) that achieve 1 and 2 log-unit immediate reductions. Frankfurters were surface-inoculated with a 10-strain mixture of L. monocytogenes (4.4 +/- 0.1 log CFU/cm(2)) and then immersed in distilled water or LA solutions (0-3%) of 4, 25, 40, or 55 degrees C for 0-120 s. A regression equation for L. monocytogenes reduction included significant (P < 0.05) effects by the terms of concentration, time, temperature, and the interaction of concentration and temperature; other tested parameters (other interactions, quadratic and cubic terms), within the experimental range examined, did not affect (P > or = 0.05) the extent of reduction. Results indicated that the effectiveness of LA against L. monocytogenes, in addition to concentration, increased with solution temperature (in the range of 0.6-2.8 log CFU/cm(2)). The developed equation may allow processors to vary conditions of treatment with LA to achieve a 1 or 2 log-unit reduction of the pathogen and comply with United States regulations.
authors.affiliation: Center for Meat Safety & Quality and Food Safety Cluster, Department of Animal Sciences, Colorado State University, 1171 Campus Delivery, Fort Collins, CO 80523, USA.
authors.forename: Oleksandr A
authors.initials: OA
authors.lastname: Byelashov
authors.forename: Hristo
authors.initials: H
authors.lastname: Daskalov
authors.forename: Ifigenia
authors.initials: I
authors.lastname: Geornaras
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Kendall
authors.forename: Keith E
authors.initials: KE
authors.lastname: Belk
authors.forename: John A
authors.initials: JA
authors.lastname: Scanga
authors.forename: Gary C
authors.initials: GC
authors.lastname: Smith
authors.forename: John N
authors.initials: JN
authors.lastname: Sofos
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D005506:Food Contamination / Q000517:prevention & control; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods; D006801:Humans; D019344:Lactic Acid / Q000494:pharmacology*; D008089:Listeria monocytogenes / Q000187:drug effects / Q000254:growth & development*; D008461:Meat Products / Q000382:microbiology*; D013552:Swine; D013696:Temperature; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D019344:Lactic Acid