Spatial distribution of population of Listeria monocytogenes during manufacturing and ripening of Camembert cheese

The spatial distribution of the survival and growth of Listeria monocytogenes during manufacturing and ripening of Camembert cheese was studied. All cheeses were artificially inoculated with L. monocytogenes and ripened in three stages: room temperature (∼20C) and relative humidity (RH) of 60% for 36 h, 13C and RH of 93% for 2 weeks, and 7C and RH of 85% for 3 weeks. During ripening, different locations were analyzed for population of L. monocytogenes. The data were collected on days 1, 5, 10, 15, 20, 25, 30 and 35 of ripening. Results showed that the population of L. monocytogenes on day 1 was 6.06 log₁₀ cfu/g, which was 1.96 log₁₀ cfu/g increasing over the initial inoculation of 4.08 log₁₀ cfu/g. For the subsequent 20 days, the L. monocytogenes population declined to 5.33 log₁₀ cfu/g. Thereafter, the L. monocytogenes population increased to 6.07 log₁₀ cfu/g on day 35 of ripening. Generally, the growth of L. monocytogenes is faster in locations near the surface than in the center. There were no significant differences between batches and sections of cheese, whereas the ripening time and locations had a significant effect on the survival and growth of L. monocytogenes. The survival and growth data for L. monocytogenes during ripening of Camembert cheese can be used to develop dynamic predictive models for possible use in risk assessment and Hazard Analysis and Critical Control Point implementation.