TY - JOUR
T1 - Efficacy of different antimicrobials on inhibition of Listeria monocytogenes growth in laboratory medium and on cold-smoked salmon
AU - Tang, Silin
AU - Stasiewicz, Matthew J.
AU - Wiedmann, Martin
AU - Boor, Kathryn J.
AU - Bergholz, Teresa M.
N1 - Funding Information:
This work was supported by New York Sea Grant R/SHH-15, funded under award NA07OAR4170010 from the National Sea Grant College Program of the U.S. Department of Commerce's National Oceanic and Atmospheric Administration , to the Research Foundation of State University of New York , and by Agriculture and Food Research Initiative grant 2010-65201-20575 from the U.S. Department of Agriculture, National Institute of Food and Agriculture, Food Safety Program . We thank Jihun Kang and Siyun Wang for assistance with the smoked salmon inoculation experiments, and Maureen Gunderson for assistance with media preparation.
PY - 2013/8/1
Y1 - 2013/8/1
N2 - Listeria monocytogenes is of particular concern in cold-smoked fish products as it can survive curing and cold-smoking, and can subsequently grow from low numbers to potentially hazardous levels during refrigerated storage. The purpose of this study was to (i) quantify the effects of organic acids, nisin, and their combinations on controlling L. monocytogenes growth on cold-smoked salmon at refrigeration temperatures, (ii) identify synergistic interactions of binary combinations of these antimicrobials, and (iii) determine if results from laboratory growth media can predict antimicrobial efficacy on cold-smoked salmon. Strains representing the genetic diversity of L. monocytogenes lineages I and II were grown in brain heart infusion (BHI) broth as well as on the surface of commercially produced wet-cured, cold-smoked salmon slices at 7°C. BHI broth and cold-smoked salmon were supplemented with sodium diacetate (SDA, 0.14% water phase (w.p.)), potassium lactate (PL, 2% w.p.), nisin (NI, 50ppm), and binary combinations of inhibitors at the same levels. Cell densities of L. monocytogenes were measured over time and used to calculate growth parameters, including initial cell density (N0), lag phase (λ), maximum growth rate (μmax), and maximum cell density (Nmax) for each antimicrobial treatment. N0 was significantly lowered by addition of NI with a similar average reduction on salmon (2.02±0.99 log(CFU/g)) and in BHI (1.51±0.83 log(CFU/ml)). Among all antimicrobial treatments, the combination of PL and SDA led to the greatest increase in λ both on salmon (7.1±3.6days) and in BHI (9.7±3.8days) when compared to the controls. The combination of PL and SDA had synergistic effects on increasing λ and lowering Nmax both in BHI and on salmon. Among all the treatments tested, the combination of NI and PL led to the greatest reductions in Nmax on salmon. We observed positive correlations between the growth parameters obtained from BHI broth and cold-smoked salmon, indicating that growth of L. monocytogenes in broth, to some extent, qualitatively reflected characteristics of growth on cold-smoked salmon under antimicrobial stresses. Results from BHI could quantitatively predict the variability of growth parameters obtained from salmon for lineage II strains, but not for lineage I strains. Although results from laboratory growth medium may not provide exact predictions of antimicrobial efficacy on cold-smoked salmon, they could be used to rapidly identify effective combinations for further examination on cold-smoked salmon.
AB - Listeria monocytogenes is of particular concern in cold-smoked fish products as it can survive curing and cold-smoking, and can subsequently grow from low numbers to potentially hazardous levels during refrigerated storage. The purpose of this study was to (i) quantify the effects of organic acids, nisin, and their combinations on controlling L. monocytogenes growth on cold-smoked salmon at refrigeration temperatures, (ii) identify synergistic interactions of binary combinations of these antimicrobials, and (iii) determine if results from laboratory growth media can predict antimicrobial efficacy on cold-smoked salmon. Strains representing the genetic diversity of L. monocytogenes lineages I and II were grown in brain heart infusion (BHI) broth as well as on the surface of commercially produced wet-cured, cold-smoked salmon slices at 7°C. BHI broth and cold-smoked salmon were supplemented with sodium diacetate (SDA, 0.14% water phase (w.p.)), potassium lactate (PL, 2% w.p.), nisin (NI, 50ppm), and binary combinations of inhibitors at the same levels. Cell densities of L. monocytogenes were measured over time and used to calculate growth parameters, including initial cell density (N0), lag phase (λ), maximum growth rate (μmax), and maximum cell density (Nmax) for each antimicrobial treatment. N0 was significantly lowered by addition of NI with a similar average reduction on salmon (2.02±0.99 log(CFU/g)) and in BHI (1.51±0.83 log(CFU/ml)). Among all antimicrobial treatments, the combination of PL and SDA led to the greatest increase in λ both on salmon (7.1±3.6days) and in BHI (9.7±3.8days) when compared to the controls. The combination of PL and SDA had synergistic effects on increasing λ and lowering Nmax both in BHI and on salmon. Among all the treatments tested, the combination of NI and PL led to the greatest reductions in Nmax on salmon. We observed positive correlations between the growth parameters obtained from BHI broth and cold-smoked salmon, indicating that growth of L. monocytogenes in broth, to some extent, qualitatively reflected characteristics of growth on cold-smoked salmon under antimicrobial stresses. Results from BHI could quantitatively predict the variability of growth parameters obtained from salmon for lineage II strains, but not for lineage I strains. Although results from laboratory growth medium may not provide exact predictions of antimicrobial efficacy on cold-smoked salmon, they could be used to rapidly identify effective combinations for further examination on cold-smoked salmon.
KW - Antimicrobials
KW - Cold-smoked salmon
KW - L. monocytogenes
KW - Nisin
KW - Potassium lactate
KW - Sodium diacetate
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U2 - 10.1016/j.ijfoodmicro.2013.05.018
DO - 10.1016/j.ijfoodmicro.2013.05.018
M3 - Article
C2 - 23803569
AN - SCOPUS:84879581812
SN - 0168-1605
VL - 165
SP - 265
EP - 275
JO - International Journal of Food Microbiology
JF - International Journal of Food Microbiology
IS - 3
ER -