Effects of Fat Content on Survival of Listeria Monocytogenes in Yogurt Fermentation and Storage

Abstract

The effect of fat content of yogurt on two Listeria monocytogenes serotypes (1/2 b and 4b) were investigated during fermentation and storage at 4°C. L. monocytogenes counts in fat-free yogurt (0.1 % fat) and in fatty yogurt (3.4% fat) decreased to an undetectable level after 5-6 days and 10-12 days of storage, respectively. L. monocytogenes serotype 4b survived longer than serotype 1/2b in both fatty and fat-free yogurt samples. The results suggested that the fat content of yogurt has a significant influence on the survival of L. monocytogenes during fermentation and storage period. In conclusion, the survival of L. monocytogenes in both fatty and fat-free yogurt samples was long enough to represent a hazard for the consumer.