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Biological surface testing limits

biological limits

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#1 KristinePlmr

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Posted 22 May 2017 - 08:26 PM

So I am looking for information regarding the acceptable control limits for Aerobic Plate counts taken on food packaging surfaces. Everything I find references a unit of CFU/cm2; however, I recently received my testing samples report back and it was in units of CFU/g? Either I need to find a table listing the cfu/g limits for food safe packaging; or I need a conversion factor from CFU/g to CFU/cm2? -Any help?


Edited by Charles.C, 22 May 2017 - 10:52 PM.
moved from older thread

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#2 KristinePlmr

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Posted 22 May 2017 - 09:04 PM

My company manufactures a component used on primary packaging, plastic reclosable zipper.

I am looking for any information on microbiological testing limits in order to review some recent testing results.

The results were given in the units of CFU/g.

Specifically Aerobic Plate Counts?


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#3 Charles.C

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Posted 22 May 2017 - 10:47 PM

My company manufactures a component used on primary packaging, plastic reclosable zipper.

I am looking for any information on microbiological testing limits in order to review some recent testing results.

The results were given in the units of CFU/g.

Specifically Aerobic Plate Counts?

 

Hi Kristine,

 

I assume yr results are effectively for one (or two) surfaces.

 

The result probably relates to the manufacturing process for the zipper and the subsequent handling / environment.

Many plastic items are produced via high temperature processes giving essentially sterile output. If so any measured result presumably derives from post-production contamination.

Some typical suggested limits for surface APC of high temp. produced paper/plastic packaging are max 1cfu/cm2 or lower.

 

Can you post your results and clarify yr production method ?

 

PS - Re -

 

So I am looking for information regarding the acceptable control limits for Aerobic Plate counts taken on food packaging surfaces. Everything I find references a unit of CFU/cm2; however, I recently received my testing samples report back and it was in units of CFU/g? Either I need to find a table listing the cfu/g limits for food safe packaging; or I need a conversion factor from CFU/g to CFU/cm2? -Any help?

 i suggest you ask the laboratory how they obtained their results. Presumably only from exposed surfaces ?.

Odd-shaped items are often problematic. Maybe can estimate the area ?.


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Kind Regards,

 

Charles.C


#4 KristinePlmr

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Posted 23 May 2017 - 12:52 PM

I do not want to post the full results or report; however, the one reading I need to verify is listed as Aerobic Plate Count at 170 CFU/g. This was taken of the finished product and would definitely represent the handling or environment of the product. It seemed definitely a bit higher than the others.  Also, most give this value as CFU/cm2? My results are in CFU/g is there an easy conversion?


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#5 GMO

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Posted 23 May 2017 - 01:13 PM

Your swab results will depend on the surface area swabbed.  Typically 10x10cm or 20x20cm for TVCs / conventional (non Listeria) swabs.  You can then calculate your results from whatever area you tell people to swab, however, I can say that we don't convert them, we just have one standard swab surface area size then leave all figures as reported.


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#6 FurFarmandFork

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Posted 23 May 2017 - 02:37 PM

I do not want to post the full results or report; however, the one reading I need to verify is listed as Aerobic Plate Count at 170 CFU/g. This was taken of the finished product and would definitely represent the handling or environment of the product. It seemed definitely a bit higher than the others.  Also, most give this value as CFU/cm2? My results are in CFU/g is there an easy conversion?

 

 

It sounds like they sampled Xg of product and stomached it with the media used to collect and grow the organisms rather than swabbing. This is common for destructive microbial testing of cardboards or other materials.

 

You need to talk to the lab and ask about the methodology they used, and if they used a standard piece of your material, determine how many cm^2 was represented in the sample and convert from there. It sounds like they did not just swab a specified surface area like you may have seen in the past. Or maybe it's just a mistake on the CoA, they happen.

 

Example: you submitted two feet of laminate. They weighed up a 10g portion and blended with 90g of sterile buffer, then plated 1g of the homogenate, then reported CFU/g material sampled. If this was the case I'd find out how many cm^2 of surface area is represented in 1g of the material and convert.


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#7 kibeda

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Posted 24 May 2017 - 11:46 AM

We swab our food contact surfaces and analyze for Aerobic Plate counts. Acceptable results for us are < 10 cfu which anything under 10 is not a significant level.


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#8 Charles.C

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Posted 24 May 2017 - 12:18 PM

I do not want to post the full results or report; however, the one reading I need to verify is listed as Aerobic Plate Count at 170 CFU/g. This was taken of the finished product and would definitely represent the handling or environment of the product. It seemed definitely a bit higher than the others.  Also, most give this value as CFU/cm2? My results are in CFU/g is there an easy conversion?

 

Hi Kristine,

 

The simple answer without contacting the lab./knowing their methodology is No.

Yr result as quoted is only directly useful if it is correlatable to a specific SOP/ target limit.

 

As per post 6, various methods are in use, typically based on swabbing or digesting with the former predominating. Hence the frequent use of cm2

 

Can try this Packaging thread if you would like to see a variety of options, methodologies, limits -

 

http://www.ifsqn.com...-for-packaging/

( i suspect some of the attachments in this thread screwed up the units also)

 

@kibeda - with all due respect, yr measurement lacks a unit.


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Kind Regards,

 

Charles.C


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