9 replies to this topic

[Ag52014]

Hi, does anyone happen to know where I can find d and z values for some microorganisms. A long search has provided nothing.

 

In particular I was looking for :

 

Staphylococcus Aureus

Staphylococcus Haemolyticus

Stenotrophomonas Maltophilia

Macrococcus Caseolyticus

Enterococcus casseliflavus

Escherichia Coli

Acinetobacter baumannii

 

Is anyone aware of any references that I can obtain this information? 

[Scampi]

This may help

 

https://onlinelibrar...1118346235.app2

 

The death rate depends on alot of factors, so you're going to have to do some fairly indepth reading to get to a full understanding of the thermal death curve

[Ag52014]

Thank you for the information.

Sorry this should say f value (thermal death time) I will try and change.


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Edited by Ag52014, 28 May 2019 - 08:40 PM.

[Charles.C]

Thank you for the information.

Sorry this should say f value (thermal death time) I will try and change.


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Hi Ag,

 

As you probably know, the D-value, z-value and TDT/ lethality (eg F₀) are all effectively cross- linked by formula(e) so (I think?) only D/z are mandatory. The search convenience  may also relate to yr specific application(?).

 

As per Post2 various practical factors can be involved.

 

Some of yr species look rather esoteric, it may help if you can provide some operational context/detail as to reason for yr request.

 

Just as an illustration, 2 of yr targets are included in the D-value Table attached however the given temperatures, food matrices, etc may not be of direct interest (although in some applications, representative "average" values are implemented)("z" also enables calculation of D vs T, see attached).

 

 D as function (T,z).PNG   8.65KB   2 downloads

 

 D-values.pdf   139.07KB   41 downloads

Edited by Charles.C, 30 May 2019 - 03:33 AM.
added

[Ag52014]

Hi Ag,

As you probably know, the D-value, z-value and TDT/ lethality (eg F₀) are all effectively cross- linked by formula(e) so (I think?) only one of the 3 is mandatory. The search convenience may also relate to yr specific application(?).

As per Post2 various practical factors can be involved.

Some of yr species look rather esoteric, it may help if you can provide some operational context/detail as to reason for yr request.

Just as an illustration, 2 of yr targets are included in the D-value Table attached however the given temperatures, food matrices, etc may not be of direct interest (although in some applications, representative "average" values are implemented).

D-values.pdf

Hi , thank you so much for the information. It is all very helpful.

The bacteria has relation to raw milk and some of which have known to be found in sterilised milk.
I wonder if some of them are Psychrotrophic bacteria causing proteolytic enzymes by thermal resistance?




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[pHruit]

It might be worth giving Campden BRI a call to find out more about the content of their Heat packaged foods: guidelines for establishing the thermal process and Validation and optimisation of thermal processing systems guide books - the equivalent document for pasteurisation (Pasteurisation: a food industry practical guide) contains quite a lot of useful data on D/z values, so I'd expect that one of these will include similar for f values. The data in the tables are also all referenced to source, so it's easy to find further information if needed (although most people in the UK would accept Campden as a sufficient reference in its own right).

If you're members then also ask to speak to someone in microbiology and/or thermal processing - IME they like interesting questions and are very knowledgeable

[Charles.C]

It might be worth giving Campden BRI a call to find out more about the content of their Heat packaged foods: guidelines for establishing the thermal process and Validation and optimisation of thermal processing systems guide books - the equivalent document for pasteurisation (Pasteurisation: a food industry practical guide) contains quite a lot of useful data on D/z values, so I'd expect that one of these will include similar for f values. The data in the tables are also all referenced to source, so it's easy to find further information if needed (although most people in the UK would accept Campden as a sufficient reference in its own right).

If you're members then also ask to speak to someone in microbiology and/or thermal processing - IME they like interesting questions and are very knowledgeable

 

Hi pHruit,

 

Yes, I agree. Campden is unquestionably a GoldMine. But only if you've got the Silver.

 

Microorganisms in Foods Vol 5 may also help but haven't checked yet.

Edited by Charles.C, 29 May 2019 - 08:30 AM.
added

[pHruit]

Hi Charles,

Yes, membership isn't a cheap pastime

But the standalone guides can be a worthwhile investment - they're around £50-100 each IIRC, and just having data and the list of references can readily save that much in the cost of the time it would take to find the info oneself.  

[Scampi]

You can also reach out to uni's................if they have a great micro lab and a down to earth head, you can often get what you need for free!!!!!!!!!!!!!!!!!!!!!!!

 

Particularly if you won't take NO for an answer ( )

[pHruit]

Great suggestion Scampi.

I've you've got more detailed things to be looked at then you may be able to reciprocate the help with some student placements / final year projects - wrong time of year now, but making contact to let them know you'd be potentially interested for next year, whilst potentially also garnering some free advice, could be a win for everybody.

You can find some surprisingly interesting things when you've got someone focussed on their own research project for your products/processes, without having all of the daily distractions (i.e. a job ) like we do...