Nisin affects the growth ofListeria monocytogenes on ready-to-eat turkey ham stored at four degrees Celsius for sixty-three days

Abstract

The objectives of this study were to determine pH, anti-Listeria and general antimicrobial properties of nisin on ready-to-eat vacuum-packaged diced turkey ham inoculated with Listeria monocytogenes, and the usage level that would exert maximum antimicrobial effect during 63 d of storage. Ready-to-eat diced turkey ham was inoculated with a 5-strain L. monocytogenes cocktail; treated with 0.2, 0.3, 0.4, and 0.5% nisin treatment solutions; vacuum-packaged; stored at 4+/-1 degrees C for 63 d; and analyzed at 1-wk intervals for total aerobic counts, pH, L. monocytogenes, and lactic acid bacteria. Antimicrobial effectiveness of nisin increased as concentration increased from 0.2 to 0.5%. Aerobic plate counts for 0.4 and 0.5% nisin were lower (P<0.05) than negative and positive controls. All nisin treatments resulted in 4 log reductions (P<0.05) in L. monocytogenes when compared with the positive control on d 0. Four log reductions were also observed on d 7 for 0.4% nisin treatment and d 7 and 14 for 0.5% nisin treatment when compared with the positive control. Listeria monocytogenes counts decreased from 4.97 log cfu/g on d 0 and remained less than 2 log cfu/g through 63 d of storage for the 0.5% nisin treatment. Lactic acid bacteria counts were lower (P<0.05) for 0.5% nisin treatment when compared with positive and negative controls from 28 through 63 d. Except for d 56 and 63, pH was similar (P<0.05) for all treatments. This study revealed that nisin could be used for postprocessing intervention to control L. monocytogenes in ready-to-eat poultry products.