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Survival kinetics of Mycobacterium bovis during manufacture and ripening of raw milk Cheddar and Caerphilly cheese produced on a laboratory‐scale
Author(s) -
Forgrave R.,
Donaghy J.A.,
Fisher A.,
Rowe M.T.
Publication year - 2016
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/jam.13278
Subject(s) - raw milk , ripening , food science , mycobacterium bovis , cheese ripening , mycobacterium , kinetics , cheesemaking , scale (ratio) , biology , chemistry , bacteria , medicine , tuberculosis , mycobacterium tuberculosis , pathology , geography , genetics , physics , cartography , quantum mechanics
Aims Persistence of Mycobacterium bovis was investigated in UK raw milk cheeses. Methods and Results Replicating traditional cheese production methods under stringent CL 3 containment conditions, Cheddar and Caerphilly cheeses were produced with Myco. bovis inoculated raw milk. High‐inoculum investigations used three Myco. bovis genotypes; later low‐inoculum investigations used only Myco. bovis AF 2122/97. High‐inoculum Cheddar ( n = 9) and Caerphilly ( n = 9) were matured for a minimum of 12 and 4 months respectively; maturation of low‐inoculum Cheddar ( n = 3) and Caerphilly ( n = 3) was up to 11 weeks. Survival of Myco. bovis was monitored by enumeration at different points throughout cheese manufacture and ripening. D values were calculated as follows: 57 and 59 days in high‐inoculum Cheddar and Caerphilly, respectively, and 41 and 24 days in low‐inoculum Cheddar and Caerphilly respectively. Conclusions Mycobacterium bovis is concentrated in cheese curd and a proportion lost with the whey. Reduction in viability during manufacturing is limited, while significant Myco. bovis inactivation occurs during maturation. Inactivation was improved, during Caerphilly ripening, when acid development was enhanced by increasing the proportion of starter culture. Significance and Impact of the Study Mycobacterium bovis inactivation data obtained could be used to inform assessment of the risk posed to consumers by raw milk dairy products.