Submitted to: Food and Nutrition Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2011
Publication Date: 7/1/2011
Citation: Hwang, C., Sheen, S., Juneja, V.K. 2011. Effects of lactate on the growth of Listeria monocytogenes, Escherichia coli 0157:H7 and Salmonella SPP., in cooked ham at refrigeration and abuse temperatures. Food and Nutrition Sciences. 2(5):464-470.
Interpretive Summary: Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella spp. have been implicated in outbreaks of foodborne illnesses linked with ready-to-eat (RTE) meat products. This study examined the effect of sodium lactate on the survival of these three pathogens in cooked ham. Cooked ham containing 0-3% lactate was inoculated with the pathogens and stored at refrigeration and abuse temperatures. The pathogens were not able to grow in ham containing 3% lactate, and E. coli O157:H7 and Salmonella spp. were not able to grow at 6 and 8 degree C, respectively. At temperatures that supported the growth, growth rates of these three pathogens were reduced by the addition of 1-2% lactate in ham. Among the three pathogens, Salmonella spp. was more susceptible to the effect of lactate. Mathematical models were developed to describe the effect of lactate on the growth rates of the three pathogens. Findings from this study will help RTE meat producers to guard against L. monocytogenes, E. coli O157:H7 and Salmonella spp. in RTE meats.
Technical Abstract: The objective of this study was to determine the effect of sodium lactate on the survival of Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella spp. in cooked ham during storage at refrigeration and abuse temperatures. Cooked ham was added with 0-3% lactate, inoculated with a multiple-strain cocktail of L. monocytogenes, E. coli O157:H7 or Salmonella spp. and stored at 4-15 degree C for up to 35 days. The growth of the three pathogens was inhibited in ham containing 3% lactate, and no growth of E. coli O157:H7 and Salmonella spp. occurred at the lowest storage temperatures of 6 and 8 degree C, respectively. In ham containing no lactate, the average growth rates were 0.256-0.380 log cfu/g for L. monocytogenes at 4-8 degree C, 0.242-0.315 log cfu/g for E. coli O157:H7 at 8-15 degree C, and 0.249-0.328 log cfu/g for Salmonella spp. at 10-15 degree C. The addition of 1% or 2% lactate significantly (P<0.05) reduced the growth rates of the three pathogens and the effect was more profound at lower temperatures. Salmonella spp. was more sensitive to the effect of lactate than L. monocytogenes and E. coli O157:H7. The results demonstrate that lactate in cooked ham reduces the growth rates of L. monocytogenes, E. coli O157:H7, and, particularly, Salmonella spp. This study indicated the effective lactate concentrations and storage temperatures that may enhance the microbiological safety of ready-to-eat ham.