5 replies to this topic

[Sharila Kwang]

Dear All,

              I have minor NC coming out of an external audit our company had for its Dairy Plant for FSSC 22000. The finding is that we need to validate the pasteurization conditions (Temp, time, flow rate) using a method such as thermal curve/lethal factor or another scientific method. He (auditor) also mentioned a Z factor and said we need to validate if the conditions we are using will kill the microb we identified as hazards.

 

Can someone explain how I can set up this thermal curve. I did some research but still not getting.

 

 

Kind Regards

Sharila

 

[3esa]

I dont know your standard, but typically published research papers are an acceptable validation. 

 

What I would likely do is use Google Scholar to search for applicable published papers that are similar to your setup and risks.

 

Here is a link to one I found, it's free to download from site.

 

http://onlinelibrary...EBDC1688.f04t01

[Cory R.]

The z-factor is dependent on the target microorganisms. A couple of good resources are:

 

Food Processing Technology: Principles and Practice (Woodhead Publishing in Food Science, Technology and Nutrition)

http://www.amazon.co...g/dp/1845692160

 

http://dairyscience....lators/help.htm

 

I've also attached a few problems I had to do for Food Processing Technology in college. It can be helpful in validating that your system is actually performing as expected. Plus its always good to know how to do the calculations of the data.

 

Hopefully this helps

Attached Files

•  Thermal Processing Math Problems.pdf   208.26KB   161 downloads

[Charles.C]

Dear All,

              I have minor NC coming out of an external audit our company had for its Dairy Plant for FSSC 22000. The finding is that we need to validate the pasteurization conditions (Temp, time, flow rate) using a method such as thermal curve/lethal factor or another scientific method. He (auditor) also mentioned a Z factor and said we need to validate if the conditions we are using will kill the microb we identified as hazards.

 

Can someone explain how I can set up this thermal curve. I did some research but still not getting.

 

 

Kind Regards

Sharila

 

Try searching this forum for "Lethality"

 

There is a freely downloadable excel program which will do the calculations and draw the curve for you.

 

Assuming you have the run data of course, and a value for the z factor.

 

From memory, the program is offered on the meathaccp website of Wisconsin university.

 

PS - the linked program in previous post is also good and there are examples of its use on this forum. Same data requirements. IMEX was a bit trickier to use but eventually impressive.

[Sharila Kwang]

Ok, lets "assume" this is all new to me. The Z-factor, the D-value everything. I will be doing more research on it but I just want to get in basic terms.

 

How do I begin? will I be spiking the system? how am I generating this data to plot the thermal curve?

why isn't mircrob. results for the batch after pasteurization enough to say that the system is performing as effectively?

[Charles.C]

Ok, lets "assume" this is all new to me. The Z-factor, the D-value everything. I will be doing more research on it but I just want to get in basic terms.

 

How do I begin? will I be spiking the system? how am I generating this data to plot the thermal curve?

why isn't mircrob. results for the batch after pasteurization enough to say that the system is performing as effectively?

 

Hi Sharila Kwang.

 

Milk pasteurization not my area but here is a simplified worked answer to yr query to illustrate the requirements.

 

 pasteurisation calculation.pdf   144.2KB   161 downloads

 

The above assumes, inter alia, that  –

 

(1) the target species is M. tuberculosis

(2) a reduction of 9 log cycles is acceptable for yr process, ie accepted as achieving destruction of (1)

(3) the system is a HTST, uniform temperature, 1-stage (or 1 relevant stage), continuous pasteurizer

(4) the D value for (1) is available

(5) the z value for (1) is available

 

In yr specific case, the calculation would be reversed from that shown so that you would measure (a) the time from yr system equipment and (b)  the two temperatures. Then calculate back to (i) F0 and then (ii) to the value of (log(N0/N)) which should be >= 9

 

If yr system does not operationally correspond to above (or the other assumptions), eg has non-uniform pasteurizing temperatures or  >1 stage then it will/may be necessary to modify the calculation, eg use software as in previous links for F0 determination. An example of a software program/output is here -

 

 Process Lethality Spreadsheet.xls   122KB   154 downloads

 

PS - Given that the time/temperature requirements are probably regulatory defined, alternative approaches to above are available and are in fact probably more common, eg -

 

http://www.nzifst.or...s/httrapps2.htm

 

PPS - as an example of, seemingly, changed assumptions for (1) and (2) above see -

 

https://www.uoguelph...-microorganisms

 

why isn't mircrob. results for the batch after pasteurization enough to say that the system is performing as effectively?

IMEX, this activity would be regarded as verification, not validation. Other interpretations might agree with you that it's validation.