Inactivation of Listeria monocytogenes on hams shortly after vacuum packaging by spray application of lauric arginate

This study measured and compared the short-term efficacy levels of lauric arginate (LAE) as a postlethality treatment against Listeria monocytogenes present on varied surfaces of large-diameter hams. Preliminary in vitro work demonstrated a 5-log inactivation of L. monocytogenes in 5,000- and 9,090-ppm LAE solutions within 180 min at 4.4 and 23 degrees C. Six different whole-muscle ham types were inoculated with L. monocytogenes at ca. 7-log CFU per ham and spray treated with between 15 and 29 ml of a 9,090-ppm LAE solution, or an equal volume of water (control), prior to vacuum packaging. After 48 h at 4.4 degrees C, populations were recovered from ham and interior packaging surfaces by using a surface rinse method with Dey-Engley neutralizing broth followed by plating on modified Oxford medium. Logarithmic reductions of L. monocytogenes exceeding 2 log CFU/cm(2) of ham surfaces were achieved by LAE treatment on all ham types. Hams with 1,129 cm(2) of surface area that had been processed by drenching in liquid smoke had 3.84 and 2.67 CFU/cm(2) 48 h following treatment with 18 ml of water or LAE, respectively, but increasing treatment volumes to 22 ml significantly reduced (P < 0.05) L. monocytogenes levels to 0.65 log CFU/cm(2). This study demonstrated the efficacy of LAE against L. monocytogenes on several ham types, thereby validating it as a postlethality treatment for inactivation of the pathogen.