INHIBITION OF LISTERIA-MONOCYTOGENES BY LACTOBACILLUS-BAVARICUS MN IN BEEF SYSTEMS AT REFRIGERATION TEMPERATURES

The ability of Lactobacillus bavaricus, a meat isolate, to inhibit the growth of three Listeria monocytogenes strains was examined in three beef systems: beef cubes, beef cubes in gravy, and beef cubes in gravy containing glucose. The beef was minimally heat treated, inoculated with L. bavaricus at 10(5) or 10(3) CFU/g and L. monocytogenes at 10(2) CFU/g, vacuum sealed, and stored at 4 or 10-degrees-C. The meat samples were monitored for microbial growth, pH, and bacteriocin production. The pathogen was inhibited by L. bavaricus MN. At 4-degrees-C, L. monocytogenes was inhibited or killed depending on the initial inoculum level of L. bavaricus. At 10-degrees-C, at least a 10-fold reduction of the pathogen occurred, except in the beef without gravy. This system showed a transient inhibition of the pathogen during the first week of storage followed by growth to control levels by the end of the incubation period. Bacteriocin was detected in the samples, and inhibition could not be attributed to acidification. Low refrigeration temperatures significantly (P less-than-or-equal-to 0.05) enhanced L. monocytogenes inhibition. Moreover, the addition of glucose-containing gravy and the higher inoculum level of L. bavaricus were significantly (P less-than-or-equal-to 0.05) more effective in reducing L. monocytogenes populations in most of the systems studied.