Effect of heat treatment on Listeria monocytogenes and Gram-negative bacteria in sheep, cow and goat milks |
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Authors: | Fiona MacDonald AD Sutherland |
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Institution: | Hannah Research Institute, Ayr, Scotland, UK |
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Abstract: | Sheep milk, compared with cow and goat milk, had a protective effect on Gram-negative bacteria and Listeria spp. heated at 65°C in a test-tube method. This effect was not solely due to fat content as cow milk artificially reconstituted to 10% homologous fat was not as protective. Listeria monocytogenes in whole sheep, cow and goat milks at an inoculum level of 1 times 106 cfu ml-1 was heated at 68°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 times 106 cfu ml-1) could not survive the current HTST plate pasteurization protocol. |
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