Thermal Inactivation of Campylobacter Species, Yersinia enterocolitica, and Hemorrhagic Escherichia coli 0157:H7 in Fluid Milk

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Abstract
Heat treatment of raw milk in an HTST pasteurizer operated at 60.0 to 72.0 degrees C for a minimum holding time of 16.2 s rapidly inactivated mixtures of hemorrhagic Escherichia coli O157:H7, Yersinia enterocolitica and Campylobacter spp. (C. fetus, C. coli, and C. jejuni). Each of the three genera in the mixture was inoculated at a level of approximately 1.0 x 10(5) cfu/ml. At 60.0 degrees C, hemorrhagic E. coli showed a maximum 2 log10 reduction in counts and no viability at greater than or equal to 64.5 degrees C. Yersinia enterocolitica and Campylobacter spp. showed greater heat sensitivity with a 4 log10 reduction in counts at 60.0 degrees C and absence of viable cells at greater than or equal to 63.0 degrees C. These findings reiterate the need for stringent control of thermal processes in the manufacture of dairy products from raw or heat-treated (non-pasteurized) milk.