Modelling and predicting the simultaneous growth of Listeria monocytogenes and spoilage micro-organisms in cold-smoked salmon.
OBJECTIVE
To evaluate and model the simultaneous growth of Listeria monocytogenes and spoilage micro-organisms in cold-smoked salmon.


RESULTS
Growth kinetics of L. monocytogenes, lactic acid bacteria (LAB), Enterobacteriaceae, enterococci and Photobacterium phosphoreum were determined in two series of challenge tests with sliced and vacuum-packed cold-smoked salmon (SVP-CSS). The product contained a high level of smoke components and at 2 degrees C levels of L. monocytogenes increased <100-fold in 193 days. Without the addition of spoilage micro-organisms, L. monocytogenes reached ca 108 CFU g-1 at 5, 10, 17.5 and 25 degrees C. Inoculation with spoilage micro-organisms reduced this level to 102-104 CFU g-1. LAB dominated the spoilage microfora of SVP-CSS and competition between LAB and L. monocytogenes in SVP-CSS was appropriately described by a simple expansion of the Logistic model. This interaction model aided in predicting the growth of L. monocytogenes in naturally contaminated SVP-CSS when it was used in combination with expanded versions of existing secondary models for L. monocytogenes and LAB.


CONCLUSIONS
Temperature, water activity/NaCl, simultaneous growth of LAB, smoke components and to a lesser extent lactate and pH control growth of L. monocytogenes in SVP-CSS. These factors must be included in mathematical models to predict growth of the pathogen in this product.


CONCLUSIONS
The suggested predictive model can be used to support assessment and management of the human health risk due to L. monocytogenes in SVP-CSS.
Giménez
B
B
Universidad de Zaragoza, Facultad de Veterinaria, Departamanto de Producción Animal y Ciencia de los Alimentos, Zaragoza, Spain.
Dalgaard
P
P
D000818:Animals; D001419:Bacteria / Q000254:growth & development; D003080:Cold Temperature; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods; D006801:Humans; D019344:Lactic Acid / Q000096:biosynthesis; D008089:Listeria monocytogenes / Q000254:growth & development*; D008954:Models, Biological; D012474:Salmon / Q000382:microbiology*
D019344:Lactic Acid