What exactly is 'slurry' ?

Discussion in 'General Brewing Discussions' started by MHR, Sep 16, 2014.

  1. MHR

    MHR New Member

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    I am looking for help in understanding exactly what the term 'slurry' means. I have brewed several batches of partial mash beer successfully, and for the last batch used one smackpack & a small amount recovered yeast to make my first starter, which fermented the wort vigorously. Now I'd like to save the cost of a smackpack (and feel like I'm taking over a little bit more of the process) by using only recovered yeast in a starter for my next batch (same kind of strong IPA, so the yeast should be suited to the task).

    My problem is that in reading brewing books such as Palmer and trying to use the yeast starter calculator on here, all the calculations & principles (declining vigor over time, cells/ml, etc) are confounded by my lack of understanding of what slurry is. I've harvested yeast from both the primary & secondary yeast cakes (didn't feel I got enough from the primary) and after washing it have ended up with a 1/4-inch layer of yeast in the bottom of a quart jar, covered with clear beery liquid. The yeast calculator starts with a default of 1 liter of slurry -- I assume that's not expecting the bottom yeast layer to amount to that much, so it must mean the yeast layer swirled up in the liquid. But since the amount of liquid in the jar depends on how much of it I discarded after the yeast settled, it doesn't make sense to me that 'slurry' can have an assumed standard yeast density. I could swirl up that amount of yeast in a half-liter of liquid, or in 2 liters of liquid -- both would be slurries, but would have greatly different densities.

    Sorry for the belabored explanation of my question, but hopefully someone will see my problem and clue me in! I want to use enough, but not too much, yeast for my starter and don't see how to properly use the calculator.

    Thanks for any advice--

    Matt
     
  2. Ozarks Mountain Brew

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    a slurry is the yeast in a thick layer kind of the consistency of syrup usually from chilling or settling to the bottom of a flask dormant, it comes that way when you order liquid yeast sometimes with a clear layer of liquid on top because it separates over time

    yeast that has fallen to the bottom of a carboy with grain solids and hop debris in it its called trub

    so a yeast slurry is all yeast nothing else, possibly your washed yest and from the secondary are considered a slurry
     
  3. MrBIP

    MrBIP Active Member

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    This is a really great question.
    How do you know how much yeast you are starting with?
    Now I'm going to have to go start doing some research. Oh darn. :D
     
  4. Arvie

    Arvie New Member

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  5. MHR

    MHR New Member

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    Ozarks - Yeah, I know what trub is. I'd like to believe you're correct in calling the settled yeast 'slurry,' but that doesn't jibe with the yeast calculator having a default of 1 liter -- that's a hell of a lot of settled yeast (in homebrewer terms).

    I read the Wyeast site and it makes me feel a little better, like I should just call what I've got 40% slurry and addit to a starter and then pitch it, I still am a bit amazed that there are all these curves and computations and no one can say with certainty what the starting point is.

    If anyone can straighten me out on this, please step in. Seems crazy that we do all these computations and worry about degradation of yeast over time, yet we don't have a definition for the substance that is the foundation for the process . . .

    MHR
     
  6. Arvie

    Arvie New Member

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    Well, if you want to go another step deeper into this you could always get a microscope and count yeast cells, then your slurry amount doesn't really matter, only your cell count.

    Found an interesting blog on the subject at:

    http://eurekabrewing.wordpress.com/2012 ... ast-cells/

    Also if you skip ahead a couple of blog posts, there is a series on yeast banking for homebrewers too.

    Hope this helps. If you find something else that might be helpful, throw it on the thread, I save almost all the yeast I brew with to reuse and trade.
     
  7. Ozarks Mountain Brew

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    I think your question was what was a slurry, not is it viable yeast for the next batch. thats another question all together and a slurry from the previous batch isn't necessarily alive so you need to add it to a starter even more so than one bought from a store just to see whats alive and whats not. in my practices I add twice the amount of used yeast for the same gravity of fresh bought yeast if that helps, even after making a starter
     
  8. MHR

    MHR New Member

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    Thanks for the replies, they were helpful, as were the links. I'm going to add the yeast I've collected to a starter, then use that, which will be greater in volume than 1 or even 2 smackpacks in my next batch and see what happens. If I can keep everything clean, I'm confident that I'll get a vigorous fermentation, and I'm gonna stop worrying about some of the details. I appreciate your help!
     
  9. GernBlanston

    GernBlanston New Member

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    Something I'm not understanding here. Brewer #26753, you mention collecting yeast to put in a starter. I wash and collect yeast so I don't have to do a starter. If I was going to make a starter every time I would just cough up the $7 bucks, and buy new yeast. You should be able to collect plenty of yeast to just re pitch. I collect enough yeast from one five gallon batch to pitch to three different batches, and from all of them I could collect even more yeast. I dump more yeast than I reuse, and still have plenty. Your five gallon batch of beer is the ultimate starter. With proper washing procedures and proper storage, you should have yeast -O- plenty.

    I keep three yeasts going all the time. I usually have a lager (currently 833 Bock), an English ale, and 001 Cal ale. This requires some forethought, so Ive got my brew schedule planned several months ahead. When I rack into the keg I collect and wash the yeast and put it in the fridge, and pull out the yeast stored from the previous batch to use in the current brew. With two fermenters full all the time, I have one yeast freshly pitched, one approaching the end of fermentation, and one in mason jars stored in the fridge. When I want to do a Belgian, I will introduce a fourth to the rotation, then dump it after a few brews.

    After about 10 beers I will dump a yeast and start out fresh, but even then w/o a starter. For the Cal Ale yeast I will brew a Scottish light 60/-, Then use that yeast cake for bigger beers. With the English Ale Yeast I will start out with a mild for the first beer. The Lager yeast I do make a small starter, but then start out with a Munich Helles, and move on from there.
     
  10. johncieera

    johncieera New Member

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    I use Mr. Marlty to figure out how much I have and then Yeastcalc to see my starter steps.
     
  11. Ozarks Mountain Brew

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    one thing to note, depending on the yeast type under or over pitching yeast can change the flavor of your beer so be very careful on how much you add
     

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