Inhibition of Listeria monocytogenes in Vacuum or Modified Atmosphere-Packed Ground Beef by Lactococcal Bacteriocins

Abstract

We investigated the antagonistic effects of two lactococcal bacteriocins, nisin or lacticin NK24, on the growth, the survival of Listeria monocytogenes in vacuum or modified atmosphere-packaged ground beef. Ground beef was inoculated with approximately 3 log colony-forming units (CFU) of L. monocytogenes ATCC 15313 culture per gram of ground beef. Inoculated samples were blended with/without 100 AU/g nisin or lacticin NK24,, subsequently vacuum or modified atmosphere packed at 4℃. Listeria in the bacteriocin-treated, control samples was subsequently isolated from both vacuum, modified atmosphere packs, enumerated as CFU on Listeria Isolation Agar medium. Microbial counts in ground beef treated with bacteriocin declined steadily, while those of non-treated beef samples increased steadily. The results obtained demonstrate that nisin inhibits the growth of L. monocytogenes more effectively than lacticin NK24 at 100 AU/g. The use of lactococcal bacteriocins, such as nisin or lacticin NK24, in vacuum or modified atmosphere packaging offers a promising approach for eliminating or reducing the risk of L. monocytogenes contamination in ground beef.