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Water Activity and Micro Activity

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Posted 07 June 2011 - 04:53 PM

Not sure if I've started this thread in the right topic area, but I think it would fit under Microbiology Talk.

I work for a tea company and we've recently started testing the water activity of our ingredients. I could really use some help in finding some good sources to base our water activity specifications on. I know when it comes to inhibiting pathogenic bacteria, we need to have water activities below 0.85-0.87. That's not really a problem because none of our products are above 0.80 (at least so far). What I'm concerned with is the water activity levels that mold can grow under, and more specifically toxic mold. However when it comes to mold growth different sources I've looked at say different things. One says 0.70 is a "practical limit" for mold (e.g. below that mold can't grow). Another one says 0.80 is the limit. I guess what I'd like to find is a resource I can trust that discusses the micro activity across the water activity spectrum.

All of our products have a fairly long "claimed" shelf life and I'd like us to be able to keep that shelf life by ensuring that the ingredients will be shelf stable and not allow mold growth. I need some good references to base this water activity limit on.

Thanks for the help,


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Posted 09 June 2011 - 09:23 PM

Any member help out Lane please?

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Posted 10 June 2011 - 02:37 AM

Dear Lane,

Try this one. It's a bit old but maybe a good start.


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Posted 12 June 2012 - 06:38 AM

even this should help you with the problem;


It's indicated in the literature that bacterial (even molds) growth is inhibited under water pressures below 0.6. However 0.80 should be sufficient in your case.

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