Submitted to: Journal of Meat Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/15/2005
Publication Date: 9/1/2005
Citation: Luchansky, J.B., Call, J.E., Hristova, B., Rumery, L., Yoder, L., Oser, A. 2005. Viability of Listeria monocytogenes on commercially-prepared hams surface treated with acidified calcium sulfate and lauric arginate and stored at 4°c. Journal of Meat Science. v. 71 (1). p. 92-99. Interpretive Summary: The food borne pathogen Listeria monocytogenes can cause serious illness in humans, particularly in high-risk individuals such as the young, old, pregnant, and immuno-compromised. In recent years there have been several significant food recalls and food borne outbreaks of listeriosis associated with ready-to-eat (RTE) delicatessen-type meats. The objective of the present study was to evaluate a novel way to deliver antimicrobials to RTE foods using 'table brown' hams as a model system. In this method, food grade chemicals effective against L. Monocytogenes were introduced into the package just prior to placement of the product into the bag by the sprayed lethality in container (SLIC) method. The resulting antimicrobial purge was then distributed throughout the package as a result of the subsequent vacuum packaging of the ham. Depending on the antimicrobial and the volume of it that was delivered to the hams, we observed an initial reduction in levels of L. monocytogenes inoculated onto the product. We also observed that the SLIC delivery method and the antimicrobials it delivered, namely acidified calcium sulfate and lauric alginate, were effective at preventing L. monocytogenes from growing during the projected refrigerated shelf life of ham. Our findings confirm that SLIC is an easy, effective, and economical method for delivery of antimicrobials to RTE meats such as hams. The SLIC method also has applications for controlling L. monocytogenes and other pathogens in a variety of RTE foods.
Technical Abstract: We demonstrated the effectiveness of delivering an antimicrobial purge/fluid into shrink-wrap bags immediately prior to introducing the product and vacuum-sealing, namely the 'Sprayed Lethality In Container' (SLIC) intervention delivery strategy, for control of Listeria monocytogenes. The antimicrobials evaluated were acidified calcium sulfate (ACS; calcium sulfate plus lactic acid; 1:1 or 1:2 in dH2O) and lauric arginate (LA; 5 or 10% in dH2O) and the product was commercially prepared 'table brown' hams (ca. 3 pounds each). Hams were surface inoculated with a five-strain cocktail of L. monocytogenes (ca. 7.0 log10 CFU per ham), added to shrink-wrap bags that contained ACS or LA, vacuum-sealed, and stored at 4°C for 24 hours. Pathogen levels decreased by 1.2, 1.6, 2.4, and 3.1 log10 CFU/ham and 0.7, 1.6, 2.2, and 2.6 log10 CFU/ham in samples treated with 2, 4, 6, and 8 mL of a 1:1 and 1:2 solution of ACS, respectively. In samples treated with 2, 4, 6, and 8 mL of a 5% solution of LA, pathogen levels decreased by 3.3, 6.5, 5.6, and 6.5 log10 CFU/ham, whereas when treated with a 10% solution of LA pathogen levels decreased ca. 6.5 log10 CFU/ham for all application volumes tested. The efficacy of ACS and LA were further evaluated in shelf-life studies wherein hams were surface inoculated with either ca. 3.0 or 7.0 log10 CFU of L. monocytogenes, added to shrink-wrap bags that contained 4.5 mL of either a 1:2 solution of ACS or a 5% solution of LA, vacuum-sealed, and stored at 4°C for 40 days. In hams inoculated with 7.0 log10 CFU, L. monocytogenes levels were reduced to below detectable limits (ca. 0.8 log10 CFU/ham) in samples treated with 5% LA and were reduced by about 1.0 log10 CFU/ham in samples treated with a 1:2 solution of ACS within 24 hours of storage at 4°C compared to control hams that were not treated with ACS or LA. Thereafter, pathogen levels increased by ca. 0.7 log10 CFU/ham after 40 days of storage in hams treated with a 1:2 solution of ACS and by ca. 3.0 log10 CFU/ham in hams treated with a 5% solution of LA. In hams that were inoculated with 3.0 log10 CFU, within 24 hours at 4°C pathogen levels were reduced by about 1.5 and 2.0 log10 CFU/ham in samples treated with a 5% solution of LA and a 1:2 solution of ACS, respectively, compared to untreated control hams. The level of L. monocytogenes in hams treated with a 1:2 solution of ACS increased by about 0.8 log10 CFU/ham after 7 days of storage, but decreased to below detection within 40 days at 4°C. Pathogen levels in hams treated with a 5% solution of LA decreased to below detection within 7 days of storage and remained below this threshold for the duration of the 40 day refrigerated storage. These data confirmed that application via SLIC of both ACS and LA, at the concentrations and volumes used in this study, appreciably reduced levels of L. monocytogenes on the surface of hams within 24 hours at 4°C and showed potential for controlling outgrowth of the pathogen over 40 days of refrigerated storage.