Effect of salt, smoke compound and temperature on the survival of Listeria monocytogenes in salmon during simulated smoking processes

Authors: Hwang, Cheng An; Sheen, Shiowshuh - Allen; Juneja, Vijay

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2009
Publication Date: 11/1/2009
Citation: Hwang, C., Sheen, S., Juneja, V.K. 2009. Effect of salt, smoke compound and temperature on the survival of Listeria monocytogenes in salmon during simulated smoking processes. Journal of Food Science. 74(9):M522:M529.

Interpretive Summary: In smoked fish processes, smoking is the only step that is capable of inactivating deadly pathogens, such as Listeria monocytogenes, that contaminate the raw fish. This study determined the survival of L. monocytogenes in salmon containing 2 to 6 percent salt and 0 to 15 parts per million of phenol (smoke compound) at simulated smoking temperatures of 40, 45, 50, and 55 degrees centigrade. The results showed that temperature is the main factor that determines inactivation of L. monocytogenes, and salt and the phenol compound contribute an added inactivation effect. A model was developed that would be used by manufacturers of smoked seafood to select concentrations of salt and the smoke compound and the smoking temperature to minimize the presence of L. monocytogenes in their products.

Technical Abstract: In smoked fish processes, smoking is the only step that is capable of inactivating pathogens, such as Listeria monocytogenes, that contaminate the raw fish. The objectives of this study were to examine and develop a model to describe the survival of L. monocytogenes in salmon as affected by salt, smoke compound (liquid smoke) and smoke temperature. Cooked minced salmon containing selected levels of salt (0, 2, 4, and 6%) and smoke compound (0, 5, 10, and 15 ppm phenol) were inoculated with a 6-strain mixture of L. monocytogenes to an inoculum level of 6.0 log10 cfu/g. The populations of L. monocytogenes in salmon during processing at 40, 45, 50, and 55 degrees centigrade that simulated cold- and hot smoke temperatures were determined, and the effects of salt, phenol, and temperature on the survival of L. monocytogenes in salmon were analyzed and described with an exponential regression. At 40 degree centigrade, the populations of L. monocytogenes in salmon decreased slightly with inactivation rates of <0.01 log10 cfu/h, and at 45, 50, and 55 degrees centigrade, the inactivation rates were 0.01-0.03, 0.15-0.30, and 2.8-3.5 log10 cfu/h, respectively. An exponential regression model was developed and was shown to closely describe the inactivation rates of L. monocytogenes as affected by the individual and combined effects of salt, phenol, and smoke temperature. Temperature was the main effector in inactivating L. monocytogenes while salt and phenol contributed additional inactivation effects. This study elicits the inactivation effects of salt, smoke compound, and temperature on L. monocytogenes in salmon under a smoking process. The data and model can be used by manufacturers of smoked seafood to select concentrations of salt and smoke compound and smoke temperature to minimize the presence of L. monocytogenes in smoked seafood.