Complete Inhibition of Low Levels of Listeria monocytogenes on Refrigerated Chicken Meat with Pediocin AcH Bound to Heat-Killed Pediococcus acidilactici Cells

Abstract

A pediocin-cell preparation from Pediococcus acidilactici H (pediocin AcH) was prepared by binding this bacteriocin to heat-killed producer cells by adjusting the pH of the medium to 6.0. This preparation, when added to irradiation-sterilized raw chicken breast meat in two experiments, had an inhibitory effect on Listeria monocytogenes Scott A during incubation at 5°C. In the first experiment, chicken with no pediocin-cell preparation (control) showed an increase of 1.9 log CFU/g, from 6.2 to 8.1 log CFU/g over 28 days from an initial challenge of about 5 log CFU/g of L. monocytogenes Scott A. A pediocin level of 2,400 AU/g decreased the Listeria monocytogenes Scott A count to 2.8 log CFU/g at 28 days. In the second experiment, at a challenge level of about 3 log CFU/g of L. monocytogenes Scott A, a pediocin addition of 2,400 AU/g caused a 1-log unit reduction at day 0, and from day 7 to 28 the counts were reduced to less than detectable levels. Conversely, counts in controls increased 1.9 log CFU/g, from 3.5 to 5.6 log CFU/g over 28 days. Although L. monocytogenes Scott A was inhibited, residual pediocin was not detectable in the exudates from treated raw chicken. Experiments with sodium dodecyl sulfate showed that the pediocin remained bound to chicken proteins and retained antilisterial activity. Conversely, pediocin did not bind as readily to cooked chicken. When bound to raw chicken before cooking, pediocin activity was found associated with the cooked chicken. Collectively, the data indicate that raw chicken treated with pediocin AcH exhibits antilisterial activity both before and after cooking, thus offering protection to consumers from foodborne illnesses caused by postprocessing recontamination and/or undercooking.