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Scientific Studies/papers on effect of low aw on microbial growth


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#1 bnue

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Posted 17 May 2018 - 01:59 PM

Hello everyone,

 

Please can someone provide links/access to scientific papers that prove at low aw (<0.3) and low moisture (almost zero) there is no potential for microbial growth? The reason for this is - we manufacture flavors and the liquid flavors we manufacture are usually made with oils (rbd sunflower, coconut, or even medium chain triglycerides) and pure FEMA GRAS chemicals. Both low risk (common sense).

 

Based on risk assessment we do not test microbial growth in our liquid flavors because of its inherent characteristics (low aw, low moisture, nature of ingredients, historical recall data) however we have an auditor who wants to see scientific justification to prove why a full microbiological profile testing is not required.( :rolleyes:

 

All of our suppliers have confirmed low risk, attested to sanitation and environmental preventive controls at their end, and said micro testing is of no value, and similarly at our manufacturing end as well we have justified good manufacturing practices including the above to account for inability to contaminate the low risk product during processing. I reached out to a lab here in the US and they volunteered to do a challenge study for >6K (would have gone for it if it was a high risk product that we were not testing for micro).

 

Please can someone help me? :helpplease:



#2 jdpaul

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Posted 17 May 2018 - 02:11 PM

From FDA, Bad Bug Book

 

 



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#3 jdpaul

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Posted 17 May 2018 - 02:11 PM

Sorry, forgot the attachment

Attached Files



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#4 FurFarmandFork

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Posted 17 May 2018 - 02:21 PM

I would agree with your suppliers that finished product microbiological testing is of little value, however they should have an environmental program in place, as inability to grow does not mean lethal. Highest risk for these refined products will be for environmental contamination post-processing. Verify they have a program in place to keep Salmonella away from their sensitive filling areas and actually clean their stuff at some frequency.

 

A semi-decent reference for control methods in low Aw foods can be found here, but does not specifically cover oils.

https://www.springer...k/9781493920617


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#5 jdpaul

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Posted 17 May 2018 - 02:26 PM

What microbiological testing do you do?



#6 jdpaul

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Posted 17 May 2018 - 02:35 PM

This may be of better value to you as well

 



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#7 bnue

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Posted 17 May 2018 - 05:14 PM

Thanks all. I have attached my risk assessment, hopefully helpful to many out here...

 

Anyways, I know this is a low risk product, silly auditor needs a statement based on scientific facts (?) so that customers can place the risk on us the supplier in ensuring there wont be any potential for microbial growth. Gosh I need to word a statement including the reasoning for not testing and at the same time agree that up to the point where the customer first opens the container, there is no risk but once container is opened then it is the customers responsibility to ensure product safety and quality is maintained. HELP ME!

Attached Files



#8 Scampi

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Posted 17 May 2018 - 05:40 PM

You are only responsible for your product until it lands at the final consumer....the same statement is true for all of us. We pack a shelf stable product that of course needs refrigerated after opening, same thing

 

I've categorized my facility as low risk and am expecting ALOT of push back from the auditor on this one, so I have backed it up with a lot of scientific data (so I don't waste my time during the audit)

 

I do not test finished product either, and would argue the point to the death---there are some products our there that when good GMPs are followed and the process is controlled, the risk just isn't there

 

Just support your RA with as many scientific relevant detail as you can. OR just for fun, run micro on your FG, 1 of each sku---validation study, you never have to repeat again


Because we always have is never an appropriate response!


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#9 Ian R

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Posted 24 May 2018 - 09:48 AM

Hi bnue

 

The lowest aW that will support growth is 0.61

at this level mould Xeromyces bisporus will growth and is credited as being the organism that grows at the lowest aW

If you have aW <0.3 then nothin g can grow, however survival is a different matter

 

The other factor relating to Xeromyces bisporus is that it is generally one;y noticeable in a product after 6-7 months, it is very slow growing.

 

If you google for extreme xerophilic mould you will find a number of papers on the subject.

Literature by Pitt & Hocking are a good source of info and readily available to justify the fact that nothing grows below 0.61 aW

 

regards



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#10 bnue

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Posted 24 May 2018 - 09:37 PM

Thanks all for your comments and simply hearing my frustration.  

 

With almost zero moisture and water activity and in absence of source of nutrients, these flavors are bacteriostatic, but had to prove it <sigh>. We had commissioned a third-party laboratory  to perform a study to confirm microbiological organisms are incapable of surviving in liquid flavors. They conducted a series of experiments to determine their survivability and selected specific microorganisms that are considered the most common and of greatest concern to the food and beverage industry. Based on their expertise, the lab determined the specific strains of these microorganisms with which to test, the length of time for the test, and the level of inoculation to be used for each sample. As expected, one study resulted in pulling sample and screening it for presence of microorganisms within 20 hours of inoculation. The readings were absent for pathogens and <10 for the others. The second study resulted in pulling samples after a week and products tested had an exponential reduction of the pathogens with the final results of all testing being <10 cfu/gram (limit of detection)! What a waste of money but at least I have scientific data as Scampi said.



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#11 bnue

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Posted 24 May 2018 - 09:38 PM

Proved absence of supporting growth as well as persistence!



#12 Charles.C

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Posted 25 May 2018 - 01:23 AM

Thanks all for your comments and simply hearing my frustration.  

 

With almost zero moisture and water activity and in absence of source of nutrients, these flavors are bacteriostatic, but had to prove it <sigh>. We had commissioned a third-party laboratory  to perform a study to confirm microbiological organisms are incapable of surviving in liquid flavors. They conducted a series of experiments to determine their survivability and selected specific microorganisms that are considered the most common and of greatest concern to the food and beverage industry. Based on their expertise, the lab determined the specific strains of these microorganisms with which to test, the length of time for the test, and the level of inoculation to be used for each sample. As expected, one study resulted in pulling sample and screening it for presence of microorganisms within 20 hours of inoculation. The readings were absent for pathogens and <10 for the others. The second study resulted in pulling samples after a week and products tested had an exponential reduction of the pathogens with the final results of all testing being <10 cfu/gram (limit of detection)! What a waste of money but at least I have scientific data as Scampi said.

 

Hi bnue,

 

Yr chosen limit of detection possibly ensured a statistically "fragile" conclusion also. Sounds like a pour plate count ?.


Kind Regards,

 

Charles.C


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#13 bnue

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Posted 25 May 2018 - 12:23 PM

Hi bnue,

 

Yr chosen limit of detection possibly ensured a statistically "fragile" conclusion also. Sounds like a pour plate count ?.

Yes Charles, why? This is not good enough? :( The lab decided the type of study and is charging over 6K for each study...



#14 jdpaul

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Posted 25 May 2018 - 01:04 PM

I think it is well known that at these conditions microbiological organisms cannot continue to grow/germinate



#15 Charles.C

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Posted 25 May 2018 - 04:07 PM

Yes Charles, why? This is not good enough? :( The lab decided the type of study and is charging over 6K for each study...

 

I guessed your "reading <10 for the others" implied nil detection for some particular sampling density ?

 

Pls inform the basis whereby the detection limit was determined to be <10cfu/gram

(eg perhaps duplicate/triplicate parallel tests, each using 1ml of a 1/10th dilution of an inoculated sample plated/incubated onto an appropriate growth medium and  all giving a negative result ?)

 


 

.


Kind Regards,

 

Charles.C


#16 Charles.C

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Posted 26 May 2018 - 05:50 AM

Hi bnue,

 

Worth noting that, as constantly reiterated on this Forum, lack of growth does not 100% prove non-survival. Neither does failure to detect/recover.

 

The minimum limit for microbial growth appears to be currently postulated as around aw = 0.6. I suppose not impossible that some super-species may be reported somewhere though. Regardless yr product looks way out of this area.

 

However the use of such data to propose product testing requirements can generate quite subtle/subjective/argumentative discussion. :smile:

 

Can have a browse through links/documents below (some more pharma oriented but i suspect of similar significance to Food) -

 

https://www.european...age-conditions/

 

https://www.ncbi.nlm...les/PMC4438321/

 

Attached File  Water activity - USP Method 1112 - Official.pdf   591.26KB   17 downloads

Attached File  Growth of microbial organisms in Foods.pdf   156.69KB   18 downloads


Kind Regards,

 

Charles.C


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#17 FurFarmandFork

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Posted 29 May 2018 - 01:39 PM

Yes Charles, why? This is not good enough? :( The lab decided the type of study and is charging over 6K for each study...

 

 

What was the inoculation level? E.g. If they inoculated 10^7 organisms into 100g of sample and recovered no organisms in a 25g sample 20 hours later, that's pretty compelling data.

 

If they added only 100 organisms and tested for presence/absence in 1g of product 20 hours later, that doesn't really mean anything.

 

The devil is always in the details. :)


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#18 Scampi

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Posted 29 May 2018 - 04:05 PM

Charles, perhaps it was that the lab has limits on the equipment they have, some will stop counting at anything less than ten. Unless your data in an anomaly, in this case it seems reasonable to me to stop at that.

Probably would have cost another $2000 to prove a true "0" and you don't really get alot for the extra $$ spent


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#19 Charles.C

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Posted 30 May 2018 - 07:14 AM

Charles, perhaps it was that the lab has limits on the equipment they have, some will stop counting at anything less than ten. Unless your data in an anomaly, in this case it seems reasonable to me to stop at that.

Probably would have cost another $2000 to prove a true "0" and you don't really get alot for the extra $$ spent

 

As you know, it's frequently a simple dilution problem of course. People just don't like MPN. Or multiple Plates.

 

If the result was <1 cfu/gram i would, personally, have been a lot more satisfied. Half-bacteria are less common.

 

I guess only bnue knows.


Kind Regards,

 

Charles.C





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