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Title: Nisin affects the growth of listeria monocytogenes on ready-to-eat turkey ham stored at four degrees celsius for sixty-three days

item Hinton, Jr, Arthur

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/21/2009
Publication Date: 1/29/2010
Citation: Ruiz, A., Williams, S.K., Hinton Jr, A., Rodrick, G., Dyeri, N. 2010. Nisin affects the growth of listeria monocytogenes on ready-to-eat turkey ham stored at four degrees celsius for sixty-three days. Poultry Science. v:89. p. 353-358.

Interpretive Summary: Contamination of ready-to-eat meat products by Listeria monocytogenes is a major concern for the meat processing industry because this bacterium is an important cause of human foodborne illnesses. The present study was conducted to determine if adding nisin to diced turkey ham could reduce the ability of L. monocytogenes to grow in the ham. Four concentrations of nisin were added to different samples of ham, and the meat was inoculated with cultures of L. monocytogenes. The inoculated meat samples were stored at 4°C for up to 63 days. Samples were analyzed each week to determine the number of L. monocytogenes and lactic acid bacteria present and the level of acidity of the meat. Results indicated that a concentration of 0.5% nisin (the highest concentration used in the study) was most effective in reducing growth L. monocytogenes and lactic acid bacteria in the ham during refrigerated storage. Adding 0.5% nisin to ham also decreased acidity of ham when compared to ham treated with lower concentrations of nisin. Although none of the nisin treatments killed all L. monocytogenes that were present in the ham, these results suggest that the addition of nisin to ready-to-eat ham may be used to reduce growth of this bacterial pathogen in refrigerated, ready-to-eat poultry products.

Technical Abstract: The incidence of Listeria monocytogenes in ready-to-eat meat products has become a major concern for the meat processing industry. The objective of this study was to determine the anti-Listeria and general antimicrobial properties of nisin at four concentrations (0.2%, 0.3%, 0.4% and 0.5%) on ready-to-eat vacuum packaged diced turkey ham inoculated with a five-strain cocktail of Listeria monocytogenes. All samples were stored at 4 ± 1°C for up to 63 d and analyzed at one week intervals for pH, lactic acid organisms and Listeria monocytogenes. Anti-Listeria effects of nisin at 0.2%, 0.3%, 0.4% and 0.5% were similar (P > 0.05) for weeks 0, 1, 2 and 7 when compared to the positive control. The data demonstrated an extended lag phase for the 0.5% nisin treatment through 63 d storage. Diced ham treated with 0.5% nisin had Listeria monocytogenes counts of less than 1.95 log cfu/g through 63 d, and lactic acid bacteria counts were lower (P < 0.05) than the positive and negative controls from 28 through 63 d storage. An increase in pH (P < 0.05) was observed for the 0.5% nisin treated hams at days 56 and 63 when compared to the positive and negative controls. Although none of the treatments completely eliminated L. monocytogenes, the overall results suggested that the antimicrobial effectiveness of nisin increased as its concentration increased from 0.2% to 0.5%. This study revealed that nisin could be used as a post processing intervention to control L. monocytogenes in ready-to-eat poultry products.