Inhibition of Listeria spp. in sterile food systems by pediocin AcH, a bacteriocin produced by Pediococcus acidilactici H

The effectiveness of pediocin AcH, a bacteriocin produced by Pediococcus acidilactici H, in reducing population levels and growth of Listeria monocytogenes strains and Listeria ivanovii in sterile ground beef, sausage mix, cottage cheese, ice cream, and reconstituted dry milk was examined. Predetermined numbers of Listeria cells and concentrations of pediocin AcH were added to the foods suspended in water and the final volumes made to 10 ml. Listeria in the pediocin AcH treated and control samples during storage at 4 and 10 degrees C were enumerated as CFU on tryptic soy agar. Results indicated that: (a) the maximum bactericidal action of pediocin AcH occurred within 1 h and was not interfered with by the foods; (b) Listeria strains differed in sensitivity to pediocin AcH; (c) reduction in CFU was greater with higher levels of pediocin AcH and as the initial cell number of Listeria spp. decreased; and (d) the surviving cells in pediocin AcH treated food samples multiplied in the presence of residual pediocin AcH during storage at 4 and 10 degrees C