EFFECT OF HEAT-TREATMENT ON LISTERIA-MONOCYTOGENES AND GRAM-NEGATIVE BACTERIA IN SHEEP, COW AND GOAT MILKS

Sheep milk, compared with cow and goat milk, had a protective effect o n Gram-negative bacteria and Listeria spp. heated at 65-degrees-C in a test-tube method. This effect was not solely due to fat content as co w milk artificially reconstituted to 10% homologous fat was not as pro tective. Listeria monocytogenes in whole sheep, cow and goat milks at an inoculum level of 1 x 10(6) cfu ml-1 was heated at 68-degrees-C for 15 s in the plate pasteurizer and survival was only detected in whole sheep milk after heating. Whole sheep, cow and goat milks containing high levels of L. monocytogenes (1 x 10(6) cfu ml-1) could not survive the current HTST plate pasteurization protocol.