Differential growth of Listeria monocytogenes at 4 and 8°C : Consequences for the shelf life of chilled products

Growth rates and lag times of Listeria monocytogenes at 4 and 8°C were compared in dairy products (milk, cream, and cheese), minced beef, and smoked salmon. Results showed that an increase in incubation temperature from 4 to 8°C leads to a significant decrease in time required to reach a given bacterial population density. The decreases were about 50% on cheese surfaces, 60 to 65% in milk and cream, and 75 to 80% in minced beef and smoked salmon. Consequences on the shelf life of chilled products are discussed on the basis of a simple and general linear relationship between the relative decrease in shelf life and generation time. This relationship was experimentally highlighted and theoretically demonstrated.