CONTROL OF LISTERIA-MONOCYTOGENES ON THE SURFACE OF FRANKFURTERS BY ACID TREATMENTS

Small numbers of Listeria monocytogenes can be isolated from packaged frankfurters. Based on previous work from this laboratory, these L. monocytogenes cells undoubtedly represent surface recontamination during peeling and packaging. We investigated organic acid dips just prior to packaging as a secondary lethal step to destroy L. monocytogenes and observed both bacteriocidal and bacteriostatic effects depending on the concentration of acid used. Acetic acid when combined with citric acid (at 2.5% each) restricted the growth and development of L. monocytogenes on frankfurters stored vacuum-packaged at 5 degrees C for up to 90 days. Other acids individually, such as lactic acid (5%) and acetic acid (5%), also suppressed the organism. A dose response effect was observed for all acids tested. A simple 2 min, surface rinse in saline was adequate to remove L. monocytogenes from frankfurter surfaces and gave recoveries similar to a stomacher method. The acid treatments appeared to be lethal and did not injure the organism. Overall, organic acid treatments appear to provide a secondary lethal step in frankfurter processing and could be an additional factorin limiting the presence of L. monocytogenes in frankfurters.