MAP & pasteurization 
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michael
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Posted: 22 Mar 2010 at 11:17pm 
First MAP is not a human pathogen. Secondly while the ingestion of very small numbers of some pathogens can result in disease the typical dose response curve for a pathogen indicates that high numbers are normally required for large numbers of people to become ill.


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johnston_01
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Tested this out. Very good but results disturbing. Heating doent kill these all there are ones that survive. Why do people not get sick?


michael
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An article looking at the effect of HTST pasteurisation on the destruction of Mycobacterium avium subsp. paratuberculosis (MAP) has been added. This is available at http://www.dairyscience.info/thermalprocessing.html. The article provides access to several calculators that enable the effect of HTST pasteurisation to be modeled.


michael
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Providing you have the Z value for the organism for which the D value (say D1)was calculated, you can calculate a D value (say D2) at another temperature (T2).
The maths required to do this is explained on p89 of Stumbo's book on Thermobacteriology which is referenced elsewhere in this site. The equation is as follows; logD2 logD1=1/Z (T1T2) If what you are doing is not critical and you do not have a Z value you can take an average value from the literature for the particular microbial group lots of risks/errors in doing this. I will sometime include a section dealing with pasteurisation and D and Z value determination along with calculators. This has been provided http://www.dairyscience.info/index.php/thermalprocessing.html . 

dort123
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Thnks! If I have a D for 150F can I covert to D72C? How?


michael
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While there is some uncertainty regarding the D value for MAP at 72C the literature suggests that the value for the most resistant strains is around 14 seconds.
This means that if milk containing 10 cells/ml of MAP was pasteurised at 71.7C for 15 seconds, less than 1 viable cell/ml would survive. However if the number of MAP was in excess of this number say 100 cells/ml then there would be survivors and this concentration effect, which may reflect on farm hygiene, may explain the small incidence of MAP found in some samples of pasteurised milk. I will provide a model showing the effects of holding time and initial MAP concentration on the number of survivors whenever I get some free time. The model and calculators can be accessed at http://www.dairyscience.info/index.php/thermalprocessing.html . 

dort123
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BTW MAP is Mycobacterium avium subsp. paratuberculosis.


dort123
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Hi can U pl explain effects of HTST on MAP. Does 7172C/15 s kill MAP? Why some say yes others no?


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