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Yeast Measurements and Dry Hopping

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  • Yeast Measurements and Dry Hopping

    I'm trying to put together a list of lab equipment I'd like to acquire for an upcoming brewery expansion, and I'm worried that dry hopping prior to yeast harvesting (a necessary evil for us) will wreak havoc on hemocytometers and centrifuges. Are there any reliable methods out there for achieving specified pitching rates with hoppy slurries?

    Thanks!

    Joe
    Ale Asylum
    Madison, WI

  • #2
    Why do you need to harvest yeast after dryhopping?
    Chris Enegren
    www.enegrenbrewing.com

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    • #3
      Usually 3-4 days after adding hops. The hops are pellets and the yeast is harvested from the bottoms of cylindroconical tanks.

      Joe

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      • #4
        If you are using a hemocytometer to assess the slurry you should be okay in that you can distinguish between the cells and the hop particles. If you pitch by weight you just have to remember that you are also adding the hop material entrained in the slurry as well. You may also have to "count" the hop material to get a feel for the amount of hop material entrained.

        But if you have 10 lb of slurry with hop material in a keg and the cell count of 1 gram of that slurry gives you x million (billion) cells per ml, you should be fine for estimating the pitching rate, regardless of the hop material.

        That said, I don't know how well hop particles will flow when filling the hemocytometer. It might take a few tests. You could mix up some extra yeast slurry with some crushed up and hydrated hop pellets in a ratio that might approximate the hop load in the cone and run a few trials with that and see if it tells you anything. If you do a couple cell counts before adding the hops to the yeast and then a few after, you might be able to figure out if it changes your math at all.

        If you are doing a spin-down to get % solids of the slurry it would be much harder to distinguish.

        After hemocytometers I think the technology goes up to the automatic cell counters such as the NucleoCounter that uses a dye that stains the nucleus of lysed cells and counts them. Those are wicked pricey, $15k or so.

        We don't harvest yeast from fermenters that have had hops added directly. We test the fermenters for micro contamination and it helps to reduce the potential variables in serial pitching if a tank does test positive. We usually - but not always - dry hop after harvesting yeast.

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