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Thread: acceptable number of bacteria in sample?

  1. #1
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    acceptable number of bacteria in sample?

    I pulled a yeast slurry from recent batch of IIPA for cell count/viability. However, in the 100ml dilution I counted a total of 10 cells of what appear to be brettanomyces. This count was from all 25 center squares on my slide. Would this be considered too many to re-pitch? Is there a standard count for wild yeast and bacteria that is being used as to determine a safe re-pitch qty? Thanks for any help.

    mark taylor
    cerveceria dos aves

  2. #2
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    Sorry to hear that you may be dealing with a possible infection in your yeast slurry. The first point to make is that unless you have a lot of experience looking through a microscope and differentiating brewing yeast and wild yeast, it's hard to get a positive ID by how the cell looks. Reliably, most operators would only be able to tell that it's not their brewing strain. To get more of an ID you'll need to plate it out on wild yeast media or send it off for PCR. Now to the main part of your question of whether there is an acceptable amount of contaminants in slurry or beer and the answer to that is not really no. Ideally you'd have no contaminants and to be able to make a decision, most folks in the QC world would argue that you would need to know what the contaminant is to determine the risk. If you have 10 cells in the counting area then you could have as many as 100,000 cells per mL and honestly more depending on your dilution factor, of that potential wild yeast which is a huge deal. Wild yeast are a big deal because they like the same conditions as your brewing yeast and are competing for the same resources. I'm not saying that you should destroy the yeast based on microscopy alone though, if you're worried then have the sample screened for contaminants and then make a decision.

  3. #3
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    Jan 2006
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    Thanks for the info.
    These odd cells are small and they appear to make a back and forth motion to move, almost as if hinged near one end. Doesn't look like pedio or lacto or acedobactor. Very strange

  4. #4
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    Quote Originally Posted by mbirdlane View Post
    I pulled a yeast slurry from recent batch of IIPA for cell count/viability. However, in the 100ml dilution I counted a total of 10 cells of what appear to be brettanomyces. This count was from all 25 center squares on my slide. Would this be considered too many to re-pitch? Is there a standard count for wild yeast and bacteria that is being used as to determine a safe re-pitch qty? Thanks for any help.

    mark taylor
    cerveceria dos aves
    To follow up what R.Cockerell said, you also have to consider that if it is wild yeast/bacteria, it will propagate up in that next batch, and more and more in subsequent batches. By the time you're at later Gens it will have increased in quantity by a significant amount. From a quality guy's opinion, better to search for a better route and get a fresh pitch rather than continue this yeast lineage...

    Good luck!

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