Thermal Death Time Studies of Brucella Abortus in Milk

Abstract

The efficacy of milk pasteurization in destroying Br~cella abortus has been studied by numerous investigators for the past quarter century. Their general conclusions were that the commercial pasteurization standard of 30 minutes at 61.7 C. was sufficient to destroy this organism. Evans (12), working with Br. abortus and Br. aborters var. lipolytic~es, reported they were killed ill 30 minutes at 52 C. and in 30 seconds at 63 C. The conclusions of Proeseholdt (24) in 1926 were that the German low temperature holding method of pasteurization assured complete inactivation of the Brucella organisms. This method of commercial pasteurization required a holding period of 30 minutes at 60 to 63 C. Park (23), employing a concentration of five thousand billion organisms per milliliter of milk (5 10~2), stated that Br. abortus was destroyed in 7i/~ to 10 minutes at 60 C., in 5 to 71/2 minutes at 61.1 C., and in 5 minutes at 62.8 C. In a series of papers, Carpenter and Boak (4, 7, 8, 9) found that the organism was destroyed in 15 minutes at 60 C., in 15 minutes at 61.1 C., in 10 minutes at 62.8 C., and in 30 to 60 seconds at 71.1 C.