ANTIBACTERIAL ACTIVITY OF THE LACTOPEROXIDASE SYSTEM AGAINST SALMONELLA-TYPHIMURIUM IN TRYPTICASE SOY BROTH IN THE PRESENCE AND ABSENCE OF A HEAT-TREATMENT

The antibacterial activity of the lactoperoxidase system (LP system) on the growth and survival of Salmonella typhimurium in tryptic soy broth (TSB) was determined. The LP system, consisting of lactoperoxidase (1 mug/ml), potassium thiocynante (KSCN) (5.9 mM) and H2O2 (2.5 mM), was found to have both bacteriostatic and bactericidal activities against strains of S. typhimurium. The bactericidal activity was clearly dependent on the initial inoculum level. Levels of 10(2)-10(5) CFU/ml were killed at 37-degrees-C as opposed to the bacteriostatic activity with inoculum levels of 10(6) 10(7) CFU/ml, which exhibited a 25-h lag. The LP system also enhanced thermal inactivation of S. typhimurium. D50-degrees-C values were > 60 min (untreated broth) and 12 min (LP system activated); corresponding D52-degrees-C-values were 20 min and 7.5 min; corresponding D55-degrees-C-values were 14 min and 4 min; corresponding D58-C-values were 5 min and 2.5 min and corresponding D60-degrees-C-values were .31 min and .20 min.