INHIBITION OF LISTERIA-MONOCYTOGENES BY LACTOBACILLUS-BAVARICUS MN INBEEF 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 w ith 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 sampl es were monitored for microbial growth, pH, and bacteriocin production . The pathogen was inhibited by L. bavaricus MN. At 4-degrees-C, L. mo nocytogenes was inhibited or killed depending on the initial inoculum level of L. bavaricus. At 10-degrees-C, at least a 10-fold reduction o f the pathogen occurred, except in the beef without gravy. This system showed a transient inhibition of the pathogen during the first week o f storage followed by growth to control levels by the end of the incub ation period. Bacteriocin was detected in the samples, and inhibition could not be attributed to acidification. Low refrigeration temperatur es significantly (P less-than-or-equal-to 0.05) enhanced L. monocytoge nes 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 pop ulations in most of the systems studied.