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Effect of acidified sorbate solutions on the lag-phase durations and growth rates of Listeria monocytogenes on meat surfaces

Cheng-An Hwang, Lihan Huang, Vijay Juneja
Journal of food protection 2015 v.78 no.6 pp. 1154-1160
Listeria monocytogenes, bacterial contamination, food contamination, food preservation, food preservatives, ham, microbial growth, models, pH, ready-to-eat foods, sorbic acid, temperature, vacuum packaging
The surfaces of ready-to-eat meats are susceptible to post-processing contamination by Listeria monocytogenes. This study quantified the lag phase durations (LPD) and growth rates (GR) of L. monocytogenes on the surfaces of cooked ham as affected by sorbate solutions of different concentrations and pH. Slices of cooked ham inoculated with a 5-strain mixture of L. monocytogenes (ca. 10**3 CFU/g) were surface-treated with sorbate solutions at 0-4% at pH 4.0-6.5, vacuum packaged, and stored at 4-12 degree Celsius for up to 45 days. The LPD and GR of L. monocytogenes were used to develop response surface models. The models estimated that the LPD of L. monocytogenes in samples treated with pH 4.0-5.5 solutions (no sorbate) were 0-11 days and the GR were 0.25-0.36 log CFU/day, respectively, at 4 degree Celsius. With the treatments of 2% and 4% sorbate, the LPD were estimated to be extended to 2-26 days and 34- greater than 45 days and the GR were reduced to 0.15-0.30 and 0-0.19 log CFU/day, respectively. At 4 degree Celsius, increasing sorbate concentration by 1% to 2, 3, and 4% at pH 5.5-4.0 led to an extension of LPD for 2-11, 10-19, and 18-27 days, while the GR were reduced by 0.037-0.055, 0.048-0.066, and 0.060-0.078 log/day, respectively. Sorbate also extended the LPD and reduced the GR of L. monocytogenes at temperatures of 8 and 12 degree Celsius. Results indicate that the sorbate concentration and pH are significant factors for reducing the LPD and GR of L. monocytogenes and sorbate combined with low pH has potential for use as a surface treatment to control the growth of L. monocytogenes on meat surfaces.