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  • Yeast Shearing

    Can anyone recommend some reading on the dangers of yeast shearing.

  • #2
    yeast doesn't shear in any significant amount. what is the problem that makes you think this is the cause?
    dick

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    • #3
      Interesting point. As I understood it certain pumps, for example centrifugal pumps, cause shear stress on yeast which is why brewers may use varieties of positive displacement pumps. Stressed yeast, or so I was told, does not perform as well as yeast in a good healthy condition. Since most of the yeast is fined out of our beers I was wondering if I needed to worry.

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      • #4
        Aha. I see your point. My tunnel vision of experience says never to use centrifugal pumps as they simply don't work well with thick yeast slurries. However, very thin yeast slurries, without much CO2 in them will pump quite happily, but if they pump, I have never used the yeast as it either, is the last of the yeast off a cone, and is considered atypical of the yeast strain, and so is not suitable for pitching, or contains so much liquid, either beer or water, that it could change the characteristics of the beer it is being pitched into.

        So the simple answer is, used a PD pump, e.g. diaphragm, peristaltic or perhaps mono pump to move pitching yeast or crop yeast slurries. I have never used a piston pump, but in theory you could do, but have simply have not heard of anyone using one mainly because of hygiene problems - they are not easy to clean and sterilise, any of the others mentioned are much easier.

        If you are pitching with fresh dried yeast, then you don't have problem with moving waste yeast with any sort of pump, in respect of effect on yeast performance.
        If you are repitching collected yeast, then if using top cropping yeast, you will almost certainly be ladling it off the top into a bucket or similar. And if collecting bottom cropping yeast, you are probably simply running the good stuff off the cone into a bucket or similar. If your setup is big enough to need to use a pump, then I suggest a peristaltic or diaphragm pump. When cleaning they need a by-pass system so the associated hoses and mains are cleaned at the correct flow rate, with the pump being run flat out to clean it as best it can.
        dick

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