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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL MODELING AND BIOINFORMATICS FOR FOOD SAFETY AND SECURITY

Location: Residue Chemistry and Predictive Microbiology

Title: The Effect of Salt, Smoke Compound, and Storage Temperature on the Growth of Listeria monocytogenes in Simulated Smoked Salmon

Author
item Hwang, Cheng-An

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 7, 2007
Publication Date: December 1, 2007
Citation: Hwang, C. 2007. The Effect of Salt, Smoke Compound, and Storage Temperature on the Growth of Listeria monocytogenes in Simulated Smoked Salmon. Journal of Food Protection. 70:2321-2328.

Interpretive Summary: Smoked salmon is a ready-to-eat refrigerated product that requires no heating before consumption. If not processed and handled properly, the product may be contaminated with Listeria monocytogenes, a pathogen that can grow at refrigerated temperature. Therefore, it is important to identify the factors that affect the growth of L. monocytogenes in smoked salmon, so control measures can be developed. This study was conducted to determine the effect of salt, a smoke compound (phenol), and storage temperature on the growth of L. monocytogenes in simulated smoked salmon. Salmon samples containing 0-10% salt and 0-34 ppm phenol were inoculated with L. monocytogenes and stored at temperatures ranging from 0 degree to 25 degree C. The time needed for the pathogen to start to grow (time to grow), its growth rate, and its maximum population reached in salmon were determined. Results showed that L. monocytogenes was able to grow in salmon containing the concentrations of salt and phenol commonly present in smoked salmon at the prevailing storage temperatures. Salt, phenol, and storage temperature all affected the growth of L. monocytogenes in salmon, in which higher levels of salt or lower storage temperatures increased the time to grow and reduced the growth rates. Higher levels of phenol also increased the time to grow of L. monocytogenes, particularly at lower storage temperatures. The effect of phenol on reducing the growth rates of L. monocytogenes was observed only at higher salt concentrations (>6%) at refrigerated and mild abuse temperatures (<10 degree C). In salmon that supported growth, the maximum population of L. monocytogenes reached in salmon was not affected by the salt, phenol or storage temperature. The data obtained from this study would be useful for estimating the behavior of L. monocytogenes in smoked salmon.

Technical Abstract: Smoked salmon can be contaminated with Listeria monocytogenes. It is important to identify the factors that are capable of controlling the growth of L. monocytogenes in smoked salmon, so control measures can be developed. The objective of this study was to determine the effect of salt, a smoke compound, storage temperature and their interactions on L. monocytogenes in simulated smoked salmon. A 6-strain mixture of L. monocytogenes (102-3 cfu/g) was inoculated into minced cooked salmon containing 0-10% NaCl and 0-0.4% liquid smoke (0-34 ppm phenol), and the samples were stored at temperatures in the range of 0 degree to 25 degree C. Lag phase duration (LPD, h), growth rate (GR, log cfu/h) and maximum population density (MPD, log cfu/g) of L. monocytogenes in salmon as affected by the concentrations of salt and phenol, storage temperature and their interactions were analyzed. Results showed that L. monocytogenes was able to grow in salmon containing the concentrations of salt and phenol commonly found in smoked salmon at the prevailing storage temperatures. The growth of L. monocytogenes was affected significantly (p<0.05) by salt, phenol, storage temperatures and their interactions. As expected, higher levels of salt or lower storage temperatures extended the LPD and reduced the GR. Higher levels of phenol extended the LPD of L. monocytogenes, particularly at lower storage temperatures. However, its effect on reducing the GR of L. monocytogenes was only observed at higher salt concentrations (>6%) at refrigerated and mild abuse temperatures (<10 degree C). The MPD, which generally reached 7-8 log cfu/g in salmon that supported L. monocytogenes growth, was not affected by the salt, phenol and storage temperature. Two models were developed to describe the LPD and GR of L. monocytogenes in salmon containing 0-8% salt, 0-34 ppm phenol, and storage temperatures 4-25 degree C. The data and models obtained from this study will be useful for estimating the behavior of L. monocytogenes in smoked salmon.

Last Modified: 8/27/2014
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