INABILITY OF HEAT-STRESS TO AFFECT SENSITIVITY OF LISTERIA-MONOCYTOGENES TO PEDIOCIN IN PORK

The effect of heat-shock (48C for 20 min) on sensitivity of Listeria m onocytogenes Scott A to bacteriocin produced by Pediococcus acidilacti ci was evaluated. Exposure of Listeria to pediocin (68, 267AU/mL) resu lted in lower number of survivors in the first 2 h of incubation in Tr ypticase soy broth at 37C compared with samples without pediocin, rega rdless of whether the cells were heat-shocked or not. Further incubati on for 24 h resulted in resumption of growth by L. monocytogenes, with counts reaching the same level as samples without pediocin. Cold stor age of Listeria in pork in the presence of pediocin (8, 192 AU/g) resu lted in a 2.0 log(10) reduction after 24 h, when compared with control s not exposed to pediocin, regardless of whether the samples were stor ed under air, vacuum, or a modified atmosphere. Prior heat-shocking di d not have an effect on sensitivity of Listeria to pediocin during sto rage. Thus, storage atmosphere and exposure to heat shock, which are k nown to induce thermotolerance in L. monocytogenes, had no effect in s ensitivity of this organism to pediocin.