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Behavior 0f Listeria Monocytogenes in the Sheep Raw Milk Cheese: A Study at Different Stages 0f Production and Shelf Life

Abstract

Cheese is a ready-to-eat food easily contaminated on the surface by undesirable microorganisms. Even if some are spoilage microorganisms, others are pathogenic such as L. monocytogenes, which have been associated with foodborne listeriosis by consumption of cheese. Here, we investigated through aging tests, the behaviour of L. monocytogenes during soft and pressed cheeses ripening and during their shelf-life. The contamination level relative to L. monocytogenes of 18 samples including fresh, soft and pressed cheeses was first assessed through microbiological analysis. Then soft and pressed cheeses manufactured from sheep raw milk, intentionally contaminated by L. monocytogenes were sampled in order to follow this pathogen behaviour during the ripening and shelf-life. The ripening period resulted in an increasing in pH and water activity. Likewise, a growth of L. monocytogenes of 0.7 log (ufc/g) and 0.6 log (ufc/g) were observed for the soft and pressed cheeses respectively. Furthermore, the storage at 4°C led to the decrease of the L. monocytogenes population without causing the total disappearance of this pathogen. Therefore, adequate hygienic practices are needed at every stage of the process to control the growth of the bacteria.

N’Guessan Elise, Amara Nassima, Soro Doudjo, Godrie Therese and Sindic Marianne

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