Submitted to: American Society of Microbiologists Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: May 4, 1997
Publication Date: N/A
Technical Abstract: Optimal time/temperature combinations for effective heat inactivation of Mycobacterium paratuberculosis were determined using either a holder-test tube method or a lab-scale industrial pasteurization method. Raw milk obtained from paratuberculosis-free cows was inoculated with 10*8 CFU M. paratuberculosis/ml, dispensed into tubes and heated at either 65, 72, 74 or 76C. Results indicate that the most effective reduction in viable bacterial numbers was achieved at 72C but mean time for optimal killing exceeded industry recommendations of 15 seconds at that temperature. Studies with the lab-scale pasteurizer were conducted in a similar manner. Raw milk (1-2 liters) inoculated with M. paratuberculosis (10*4 or 10*6 CFU/ml) was circulated at 72C for 15 seconds. Results from all experiments conducted with the lab-scale pasteurizer demonstrate that treatment of raw milk inoculated with live M. paratuberculosis at 72C for 15 seconds effectively killed all the bacteria. Further experiments evaluating thermal tolerance of the bacterial inocula at 55, 60, 65, 70 and 75C indicate that all bacteria were heat inactivated when treated at 65C for 15 seconds.