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194 degrees F - does it have to be 10 continuous minutes

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#1 Marshenko


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Posted 09 October 2013 - 11:21 AM

I clearly have no microbiological background, so ...


Dealing with the inactivation of C.botulinum type B per FDA Appendix 4, table A-4 below.


Our data logger in clam chowder had a couple of "blips" where the product temperature fell slightly below 194, and so I've got a span of 7 continuous minutes, then a minute under, then another 6, then a minute under, and then another 7.


My question - does the 10 minutes @ 194F need to be continuous, or can it cumulative?  Also, any reference material stating one way or another would be most appreciated.




Table A-4 contains information on the destruction 
of Clostridium botulinum (C. botulinum) type B 
(the most heat- resistant form of non-proteolytic 
C. botulinum). Lethal rate, as used in this table, is 
the relative lethality of 1 minute at the designated 
internal product temperature as compared with 
the lethality of 1 minute at the reference product 
internal temperature of 194°F (90°C) (i.e., for 
temperatures less than 194°F (90°C), z = 12.6°F 
(7.0°C); for temperatures above 194°F (90°C), 
z = 18°F (10°C)). The times provided are the 
length of time at the designated internal product 
temperature necessary to deliver a 6D process 
for C. botulinum. The values in the table are 
generally conservative. However, these values 
may not be suficient for the destruction of non­
proteolytic C. botulinum in dungeness crabmeat 
because of the potential protective effect of 
lysozyme. You may be able to establish a 
shorter process time for your food by conducting 
scientiic thermal death time studies. Additionally, 
lower degrees of destruction may be acceptable 
in your food if supported by a scientiic study of 
the normal innoculum in the food. 



#2 Charles.C


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Posted 09 October 2013 - 01:04 PM

Dear Marshenko,


I assume you are aware of the various textual caveats regarding  the use of  the tabulated data, eg with respect to the product itself, potential initial load of the target pathogen. I also presume the datalogger is accurately recording an appropriately located core temperature.


These things can be mathematically tricky so preferably don't take my single word for it if the conclusion is of critical importance as I suspect it may be.


Chapter 16 of (probably) the same reference as yr own ( Fish and Fishery Products  Hazards and Controls Guidance, 4th ed 2011) indicates the time for 6D is cumulative or to be more precise a "minimum cumulative total lethality of F (194°F )(90°C) = 10 minutes". AFAIK, this implies (if you are mathematically inclined) or have the software, you can also add the lethality effects at the temperatures below 194degF after appropriate adjustment of the z-value as indicated in text (the "bonus" is immaterial in yr quoted example of course).


Attached File  Chapter 16 Pathogenic Bacteria Survival Through Cooking or Pasteurization.pdf   1.99MB   56 downloads

(see pg 316)


Rgds / Charles.C


PS - This is only one reference of course. It is not impossible that other texts may favour the "continuous" version. Some treatments [canning i think from memory] conservatively ignore any lethality due to a "postulated"  come-up/come-down time so then tend to specify a fixed temperature / time. i hv always used the whole curve for pasteurization of shrimps but total time was much shorter due targetted on L.monocytogenes.

Kind Regards,



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#3 RuiM


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Posted 09 October 2013 - 10:13 PM

Page 72, 3rd paragraph. Attached File  Microorganisms in foods 6.pdf   26.7KB   36 downloads


Book: Microorganisms in foods 6, Microbial Ecology Of Food Commodities, Second Edition, 2005 by Kluwer Academic/Plenum Publishers.


Last paragraph. Attached File  2012 THERMAL FOOD PROCESSING New Technologies and Quality Issues.pdf   30.49KB   43 downloads


Book: Thermal Food Processing: New Technologies and Quality Issues, Second Edition, Contemporary Food Engineering, 2012, CRC Press

Edited by RuiM, 09 October 2013 - 10:14 PM.

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#4 scppvjune


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Posted 11 October 2013 - 08:36 AM

Hello Marshenko,

First of all, what kind of business you are working with.

If you worked with Low acid canned food (LACF) manufacturer, you need to hire competence Process Authority to validate your sterilizing/cooking/retorting process. You should not validate your sterilizing/cooking/retorting process by yourself since it will lead to several questions and potential for critical non-conformity during assessment by authority and/or external auditor.

If you worked with restaurant, I don't think C.botulinum is your target to concern if the soup is not packed in sealed container (anaerobe condition).

To answer about your inquiry about time and temperature in general, the cooking process should sufficient to proof that the target organism (both in vegetative form and spore form) in specific product (under control factors) is destroyed. Normally, it calculted based on log cycle of each organism.

There are several factors that need to be considered/controlled when performing heat penetration test to get proper cooking time and temperature for each product. Talking about clam chowder, I will think of characteristic of thickening agent, size of ingredients (e.g. clam, potato), ratio of solid vs. liquid, size of container, and of course thermal distribution (of your cooking/sterilizing/retorting machine). Well, competence Process Authority should be able to inform you the actual factors which might be more or less.


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