Reusing yeast cakes

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zero_gabe

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So as any other homebrewer looking to save a few bucks, I'm looking into reusing yeast as a mean to saving money. I tried spening some time online seeing if it okay for me to just throw my wort on a fresh yeast cake. I have read so many opinions and school of thoughts behind doing this. I would just like a somewhat clear direction as to if it is okay or not to do this. What are the pros and con of this. What are your guys experience doing this? Thanks for your time and help people!
 

SteveHeff

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I have never done this. I have seriously thought about it, for the same reasons you are. I ran this idea by a friend of mine, who operates his own independent brewery in Switzerland.

His advice to me: there are better guarantees in purchasing your yeast instead of reusing it. You are better off buying your yeast KNOWING that it will give you results rather than attempting to reuse something that holds a much higher risk of ruining a batch of beer.

Then again, he was brewing up to 200 gallons at a time, so a bad batch of yeast equates to a lot of money.
 

Qhrumphf

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Repitching is great, but pitching on a yeast cake is usually a bad idea.

Pros (compared to other repitching methods):
-Fast and easy
-Least risk from a sanitation perspective

Cons:
-Easy to overpitch and destroy ester character
-High percentage of dead yeast can increase risk of autolysis
-Overpitching plus other compounds can increase fusels
-Residual trub plus trub from new wort can increase staling
-Residual hops and other flavor compounds can lend off-flavors, or carry over potentially unwanted flavors

Point is, it's not advisable from a beer flavor and stability standpoint. And these dwarf the sanitation risks compared to other methods assuming your sanitation is up to snuff (and if it's not, you shouldn't be repitching anyway since you'll just multiply whatever bad guys are already there)

Now, there are a few cases where pitching on a whole yeast cake may not be a bad idea- going from a small beer like an Ordinary Bitter to a behemoth like a Barleywine or RIS that needs that big of a pitch rate. But for an average batch, it's not a good idea.

Basically, if you want to save money on yeast, try repitching properly. A lot of folks like to go the "overbuilt starter" method, where you make starters larger than you need, and save the extra yeast for later. I don't personally do it, but there's nothing wrong with it. I use a mix of top cropping (harvesting from the kräusen early on in fermentation, very fast and easy, but only works with some yeast strains) and rinsing out the yeast cake. There's threads on how to do it on HBT, but it basically involves using boiled and cooled water to separate good healthy yeast from trub/hops/dead yeast, as well as allowing you to then measure how much yeast you have, and pitch appropriately, mitigating all the issues from above. The only downside is that when doing this, your cleaning/sanitation must be absolutely impeccable, and it takes a little bit of time.
 

Yooper

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I save yeast all the time. I only buy liquid yeast a couple of times a year.

I do this: https://www.homebrewtalk.com/showthread.php?t=519995

You don't want to pitch right on your old yeast cake, except in rare circumstances. Say, making a 5 gallon dopplebock lager and you need a 3 gallon starter anyway, so I'd go ahead and make a 3 gallon light lager and then use the yeast cake for that. But otherwise, it'd be grossly overpitching.
 

DurtyChemist

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Your post will simply regurgitate your research. People still havent changed opinions. I'd say do it and see how it goes for you personally. Maybe do like some and start with a light beer, pitch an amber, then do a dark high gravity beer.
 
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