title: Inactivation of Mycobacterium bovis ssp. caprae in high-temperature, short-term pasteurized pilot-plant milk.
abstract: Experiments to determine the efficacy of high temperature, short time (HTST) pasteurization of milk in terms of inactivation of pathogenic microorganisms were mainly performed between 1930 and 1960. Among the target organisms were Mycobacterium bovis and Mycobacterium tuberculosis. As a result, the Codex Alimentarius prescribes that HTST treatment of milk should lead to a significant reduction of pathogenic microorganisms during milk pasteurization. Due to the development of improved methods for the detection of survivors and of more advanced heating technology, verification of this requirement seemed to be necessary. To address recent outbreaks of tuberculosis in cattle caused by M. bovis ssp. caprae (M. caprae) in the southern regions of Germany, this organism was tested and compared with M. bovis ssp. bovis (M. bovis). Experiments were performed in a pilot plant for HTST pasteurization of milk with 3 strains of M. caprae and 1 strain of M. bovis. In preliminary trials at a fixed holding time of 25 s, the temperature at which significant inactivation occurred was 62.5°C for all strains. To determine D-values (decimal reduction times) for the inactivation kinetics, the strains were tested at 65, 62.5, and 60°C at holding times of 16.5, 25, and 35 s. At 65°C, the D-values of all strains ranged from 6.8 to 7.8 s, and at 62.5°C, D-values ranged from 14.5 to 18.1 s. Low inactivation was observed at 60°C. When the low slope of the inactivation curve allowed calculation of a D-value, these ranged from 40.8 to 129.9 s. In terms of log10 reductions, the highest values for all strains were 4.1 to 4.9 log at 65°C, with a holding time of 35 s. The tested strains of M. caprae and M. bovis showed similar low resistance to heat. Standard HTST treatment should result in a high reduction of these organisms and thus the requirements of the Codex Alimentarius for inactivation of pathogens by this process are far exceeded.
authors.affiliation: Department of Safety and Quality of Milk and Fish Products, Max Rubner-Institute, Federal Research Institute of Nutrition and Food, 24103 Kiel, Germany. Electronic address: philipp.hammer@mri.bund.de.
authors.forename: P
authors.initials: P
authors.lastname: Hammer
authors.affiliation: National Reference Center for Mycobacteria, Forschungszentrum Borstel, 23845 Borstel, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Richter
authors.affiliation: National Reference Center for Mycobacteria, Forschungszentrum Borstel, 23845 Borstel, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Rüsch-Gerdes
authors.affiliation: Department of Safety and Quality of Milk and Fish Products, Max Rubner-Institute, Federal Research Institute of Nutrition and Food, 24103 Kiel, Germany.
authors.forename: H-G C
authors.initials: HG
authors.lastname: Walte
authors.affiliation: Department of Safety and Quality of Milk and Fish Products, Max Rubner-Institute, Federal Research Institute of Nutrition and Food, 24103 Kiel, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Matzen
authors.affiliation: Department of Safety and Quality of Milk and Fish Products, Max Rubner-Institute, Federal Research Institute of Nutrition and Food, 24103 Kiel, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Kiesner
mesh_terms: D000818:Animals; D006358:Hot Temperature; D007700:Kinetics; D050296:Microbial Viability; D008892:Milk / Q000382:microbiology*; D009163:Mycobacterium bovis / Q000502:physiology*; D061352:Pasteurization
keywords: Mycobacterium caprae; heat inactivation; milk; pilot plant