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Microbiological testing of whole herb (berry, root, etc.)

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matthewcc

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Posted 15 February 2024 - 12:25 AM

Hello, I have a question about microbiological testing of whole, dried herb (berry, root, etc.).  I asked a couple of coworkers in our in-house lab, and they had no response.  If we have a whole herb, say a whole berry, then wouldn't we want to grind it to a powder for microbiological testing? 

 

It seems to me (and by the way, I have no background in microbiology, other than from my work experience relating to our in-house microbiological testing) that, if we test a whole berry, and we don't grind it to a powder or do some size reduction, then the only surface that the micro test "sees" is the outer surface, and if there are any microorganisms in the interior of the berry, then the test result would potentially be falsely low because it doesn't detect the microorganisms inside the plant part.

 

There have been a few instances where I thought this was relevant to our test results:  For example, we test a whole herb and it meets our micro specifications, then we mill it to a powder and we are surprised that now the powder has a nonconforming micro result.  Another example is we test a whole herb and it meets our micro specifications, then we set it in extract (ethanol/water, with the processing including grinding up the herb in a vertical mixer), and then the extract with ~45% alcohol has a high micro result.

 

Therefore, from what I can tell, both in theory and in practice, we are getting falsely low micro results when we test the whole herb for micro without grinding it up.

 

I took a glance at ASTA (https://www.astaspic...crobial-safety/) and I didn't see anything on there about this, as far as I could tell.

 

Is grinding to a powder a recommended practice for microbiological testing of herbs, microbiologically, and are there methods that say that?  I want to have a good basis for making a procedural change, if we should do that.

 

We are certified SQF and NSF GMP in the United States and under 21 CFR Part 111 (dietary supplements) and Part 117.

 

Thank you,

Matthew



Quality Ben

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Posted 15 February 2024 - 05:57 AM

I have no direct experience with dried herbs or berries - but your train of thought tracks to me.

When testing for microbiological parameters - it is usual to composite and homogenise to ensure a representative result......I see no reson why this woldn't apply to dried herbs and berries. Otherwise, as you mention, you are essentially only testing the outside of the product. There may be contamination within (depending on the product matrix , processing, drying etc) and this (while may not have potential for growth due to low aW, may have potential for survival until conditions permit. 



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G M

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Posted 15 February 2024 - 04:48 PM

Our finished goods samples are ground into fine particles then 'suspended' in liquid to maximize the homogenization.  I would expect something similar for most ingredient level micro testing.



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jfrey123

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Posted 15 February 2024 - 05:18 PM

I started in a spice/dried vegetable processing plant where we would grind/blend/package either diced product or powdered versions.  We were a third party operation where we never owned the product, only grinding or packaging customer's product upon their order.  We'd often get similar situations to what you're describing:  say a diced dried carrot tests great as a whole when sampled, but we'd grind it and sample for the customer and they'd complain about micro counts.  There always ended up being finger pointing between my management and the customer:  they'd claim product must've been internally dirty and customer would claim our process dirtied the product.

 

Based on my experience there, it would be worth a shot to do comparison samples of your input material.  Send some berries whole for micro, find a sanitary way to grind or at least break up some more out of the same batch and see how the tests compare.  If those samples come back similar, unfortunately, you might need to evaluate your process to see if it is potentially contributing to increased micro.



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