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Sometimes referred to as "yeast washing," the process of yeast rinsing separates the yeast from the hops and break material in the trub. Most brewers who reuse yeast — and store it for long periods — seem to prefer the rinsing method. Some brewers simply store the trub in one or several sanitized jars. After storing this trub in the fridge, they will then either reuse this yeast directly or create a starter with it.

Has anyone tried both methods? If you reuse the trub directly, how long have you stored this yeast, and have you ever noticed off flavors? What are the pros and cons of both methods?

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I have tried both methods repeatedly and don't really see any difference. I have stored yeast with trub up to 5 months and have gotten great results reusing it once I made a starter. I recently made back to back batches of rye IPA, one with yeast mixed with trub, the other from the same yeast slurry that had been rinsed. There was no difference in either yeast performance or flavor.

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I would imagine that if you dumped the trub from a belgian dark into a blond that could affect your color profile. Or if you dump IPA trub into a low hopped cream ale or something it could affect bitterness. So in those cases washing would help minimize these factors. –  Mattress May 17 '11 at 22:08
    
How did you store the trub for 5 months? Refrigerated? Room temp? –  Jeff Roe May 18 '11 at 2:03
    
You should always store trub/slurry in the fridge. I use a sanitized 1/2 gal. plastic tub with a snap on lid. –  Denny Conn May 18 '11 at 15:34
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I'm storing a quart or so of trub from a sour beer in my fridge now. This is good to know because I won't be sure if the beer it makes is any good for a few more months. I'll leave the trub alone in the fridge and if the sour beer is good, I'll start the next one with the old trub. –  Graham May 18 '11 at 18:30
    
If you wait more than a month to use it, I'd recommend using part of the slurry to make a new starter. –  Denny Conn May 18 '11 at 19:10
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Once again, I wholeheartedly disagree with Denny.

Usually when homebrewers are talking about reusing yeast and trub, they're referring to the practice of fermenting new wort on an old yeast cake. This topic has come up several times before - you can search for "yeast cake" to see a few examples, but I think the general consensus here is that reusing the yeast cake is bad.

However, the biggest problem with that method is that the pitch rate is way too high, and pitch rate affects flavor - especially esters, and damages head retention. And overpitching over several generations of yeast results in unhealthy yeast. You could store unwashed trub, though, per your question, and pitch the correct amount of yeast with old trub mixed in.

In that case, the effects are generally minimal, to the point that other variables in your brewing setup and recipe would probably have more effect on the beer flavor.

Washing is also more important if you brew many batches with the same yeast, where yeast health is more critical.

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Brandon, it doesn't seem like we're in disagreement. You say "You could store unwashed trub, though, per your question, and pitch the correct amount of yeast with old trub mixed in" which is the same thing I was saying. I guess we do disagree when you say "reusing the yeast cake is bad.". If it's so bad, why do so many brewers get good results doing it? Jamil (mrmalty.com) endorses it here...mrmalty.com/pitching.php#s5 . Can you explain what you mean? –  Denny Conn May 18 '11 at 18:01
    
reusing the whole cake at once is sort of "bad". But repitching yeast from a batch is a great way to make great beer when done right. And many brewers do it, FYI. –  brewchez May 19 '11 at 12:05
    
what brewchez said... –  Brandon May 19 '11 at 17:09
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I generally rinse the yeast, separating it from the trub / hop bits before storing it. I've stored it for quite awhile in the fridge and never had a problem. I believe that it was the brewing network that mentioned this is a good practice for some yeasts, such as Oktoberfest. I've even rinsed the next generation and reused it. After about 4 times I stop though, just in case there's any mutations.

The rules I've always followed for rinsing are:

  • I rack to secondary, and take the yeast from the primary. I don't want the late floculating yeast.
  • I always go from lighter to dark beers, never the other way.
  • I never re-use the yeasts from high gravity beers, they are already stressed enough.

As for pitching on a yeast cake, I've found this helpful for high gravity beers. I'll brew a nice blonde or bitter, and then pitch a stout onto the yeast cake. High gravity beers are hard on the yeast, and they can putter out during fermentation. The yeast cake helps to ensure there's enough yeast to finish the job.

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With all that said...

There are a few instances that pitching the whole cake is a good thing.

Examples: Edwort's Oktoberfest ale is poured right onto the cake left from his kolsch recipe. As in you brew the Kolsch purposely to have the cake to ferment the Oktoberfest with. After brewing these brews it occurred to me that this would work for another beer. So I brewed a fairly mild pils to have a large cake to dump a DFH 90 min clone on. Worked GREAT!!

These are specific examples of when it is a good idea to dump on a whole cake. Generally though I don't recommend it for the reasons stated above by those more knowledgeable than I.

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