Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/3/2004
Publication Date: 12/1/2004
Citation: Stabel, J.R., Lambertz, A.M. 2004. Efficacy of pasteurization conditions for the inactivation of mycobacterium avium subsp. paratuberculosis in milk. Journal of Food Protection. 67(12):2719-26. Interpretive Summary: Mycobacterium paratuberculosis, the causative agent of Johne's disease in ruminant animals, has been linked as a causal agent of Crohn's disease in humans. Although similarities between Crohn's disease and Johne's disease do exist as both are chronic inflammatory disorders of the small intestine, there are distinct differences as well. The etiology of Crohn's disease is not well-defined at this time despite rigorous efforts by researchers to identify a specific pathogen for this disease. Indeed, evidence to date does not prove that Crohn's disease is caused M. paratuberculosis and may, in fact, be a multifactorial disorder. Regardless, it has become a concern for the dairy industry as consumer confidence has been influenced by reports that pasteurization may not destroy the bacterium. The present study evaluated current pasteurization standards in the US in the heat inactivation of M. paratuberculosis in UHT milk. Results of the study indicate that pasteurization by US standards effectively destroys high levels of M. paratuberculosis in milk. These data address consumer concerns about the safety of milk.
Technical Abstract: Mycobacterium avium subsp. paratuberculosis, the causative agent of a chronic enteritis in ruminants (Johne's disease), has been linked to Crohn's disease in humans. This microorganism is shed primarily in the feces by infected animals but is also shed in the milk at much lower levels. Therefore, dairy products from infected animals may be one mode of transmission of this animal pathogen. This study was designed to evaluate the effectiveness of the holder and high-temperature short-time pasteurization (HTST) standards on the destruction of M. paratuberculosis. A total of 180 experiments were conducted in this study using a slug-flow pasteurizer unit and a laboratory scale pasteurizer unit. Ultra-high temperature milk (UHT) was inoculated at 2 levels, 108 and 105 cfu/ml, with 3 different field strains of M. paratuberculosis. Five different time/temperature combinations were evaluated: 62.7°C for 30 min; 65.5°C for 16 sec; 71.7°C for 15 sec; 71.7°C for 20 sec; and 74.4°C for 15 sec. Three replicates of each experiment were run for the pasteurizer unit, time/temperature, and strain of M. paratuberculosis. Treatment of milk regardless of bacterial strain or pasteurizer unit resulted in an average 5.0 and 7.7 log10 kill, respectively, for the low and high level of inoculum. Milk treated for cheese production (65.5°C/16 sec) resulted in a much lower and more variable kill. Results from this study indicate that the current US standards for batch and HTST pasteurization are effective in significantly reducing the survivability of M. paratuberculosis in milk.