Growth Behavior of in a Traditional Norwegian Fermented Fish Product (), and Its Inhibition through Bacteriophage Addition.

may persist in food production environments and cause listeriosis. In Norway, a product of concern is the traditional and popular fermented fish product "", which is made from freshwater salmonid fish by mild-salting and brine maturation at low temperatures for several months. It is eaten without any heat treatment, and , therefore, poses a potential hazard. We investigated the effect of salt and temperature on the growth of in during the 91 days of maturation. The amounts of organic acids produced during fermentation were too low to inhibit growth of . Temperature was clearly the most important parameter for controlling . At 7 °C, approximately 2 log growth was observed during the first 14 days of fermentation, and the level of thereafter remained constant. At 4 °C, only a little growth potential of the pathogen was recorded. We also investigated the effect of the anti- bacteriophage P100 on with added . The phage was introduced to the -inoculated fish before fermentation, and an average of 0.9 log reduction was observed throughout the fermentation period. This is the first study of behavior in and points to possible measures for increasing the product safety.