title: Retrospective analysis of a listeria monocytogenes contamination episode in raw milk goat cheese using quantitative microbial risk assessment tools.
abstract: In 2005, the Belgian authorities reported a Listeria monocytogenes contamination episode in cheese made from raw goat's milk. The presence of an asymptomatic shedder goat in the herd caused this contamination. On the basis of data collected at the time of the episode, a retrospective  study was performed using an exposure assessment model covering the production chain from the milking of goats up to delivery of cheese to the market. Predictive microbiology models were used to simulate the growth of L. monocytogenes during the cheese process in relation with temperature,  pH, and water activity. The model showed significant growth of L. monocytogenes during chilling and storage of the milk collected the day before the cheese production (median increase of 2.2 log CFU/ml) and during the addition of starter and rennet to milk (median increase of 1.2 log  CFU/ml). The L. monocytogenes concentration in the fresh unripened cheese was estimated to be 3.8 log CFU/g (median). This result is consistent with the number of L. monocytogenes in the fresh cheese (3.6 log CFU/g) reported during the cheese contamination episode. A variance-based  method sensitivity analysis identified the most important factors impacting the cheese contamination, and a scenario analysis then evaluated several options for risk mitigation. Thus, by using quantitative microbial risk assessment tools, this study provides reliable information to identify  and control critical steps in a local production chain of cheese made from raw goat's milk.
authors.affiliation: Faculty of Veterinary Medicine, Department of Food Science, University of Liège, Sart-Tilman, B43bis, 4000 Liege, Belgium. l.delhalle@ulg.ac.be
authors.forename: L
authors.initials: L
authors.lastname: Delhalle
authors.forename: M
authors.initials: M
authors.lastname: Ellouze
authors.forename: M
authors.initials: M
authors.lastname: Yde
authors.forename: A
authors.initials: A
authors.lastname: Clinquart
authors.forename: G
authors.initials: G
authors.lastname: Daube
authors.forename: N
authors.initials: N
authors.lastname: Korsak
mesh_terms: D000818:Animals; D001530:Belgium; D002611:Cheese / Q000382:microbiology*; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D005506:Food Contamination / Q000032:analysis*; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006041:Goats / Q000382:microbiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008089:Listeria monocytogenes / Q000254:growth & development* / Q000302:isolation & purification; D008892:Milk / Q000382:microbiology; D008954:Models, Biological; D012189:Retrospective Studies; D018570:Risk Assessment; D013696:Temperature; D013997:Time Factors