Nisin, rosemary, and ethylenediaminetetraacetic acid affect the growth of Listeria monocytogenes on ready-to-eat turkey ham stored at four degrees Celsius for sixty-three days

The objectives of this study were to determine the anti-Listeria and general antimicrobial properties of nisin, rosemary, and EDTA alone and in combination on Listeria monocgtogenes inoculated on ready-to-eat vacuum-packaged diced turkey ham and to ascertain the effects of the treatments on pH and objective color. The turkey hams were cut into 0.5-cm pieces, inoculated with a L. monocytogenes cocktail containing 5 strains of the bacterium, and treated with either no treatment and no inoculum (negative control), inoculum only (positive control), 0.5% nisin, 20 mM EDTA, 1% rosemary, 0.5% nisin + 20 mM EDTA, 0.5% nisin + 1% rosemary, 0.5% nisin + 20 mM EDTA + 1% rosemary, or 20 mM EDTA + 1% rosemary. All samples were vacuum-packaged, stored for 63 d at 4°C ± 1°C, and analyzed at 1-wk intervals for total aerobes, L. monocytogenes, lactic acid organisms, pH, and objective color. Nisin, nisin with rosemary, nisin with EDTA, and nisin with rosemary and EDTA treatments reduced (P < 0.05) L. monocytogenes counts by 4.42, 4.20, 3.73, and 4.11 log cfu/g when compared with the positive control, respectively, on d 0. Listeria monocytogenes counts remained less than 2.75 log cfu/g for all hams treated with nisin. The EDTA and rosemary treatments alone and in combination were ineffective in inhibiting growth of L. monocgtogenes. Although none of the treatments completely eliminated L. monocytogenes, the results indicated that ready-to-eat turkey ham can have significantly decreased L. monocytogenes when treated with nisin alone or in combination with rosemary or EDTA, or both.