keg fermenting and reusing yeast, pitching fresh wort into a "dirty" keg

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odie

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I've recently moved into fermenting and serving from the same keg. Initially with a bottom tube to harvest and reuse the yeast before drinking. Now I'm using floating dip tubes so I cannot harvest any yeast.

My last couple kegs that kicked I just left them cold in the kegerator. I then brewed up another batch of the same and pitched it into the dirty kegs and let it go again.

What I've noticed both times is that when I opened the kegs, there appeared to be very little yeast cake left compared to what you normally find in the bottom of your fermenter. I assume that when the keg "blew", that last pint took a lot of the yeast cake with it. I pitched around 80' (the limit of my IC and patience) into a 40' keg and stuck it in the ferm chamber at 65'. Both times there was zero observed activity from the blow off tube until 24-48 hours.

Is this time lag due to cold shocked yeast? Should I pull the keg out and let it warm up the yeast cake while I'm brewing?

Is this possibly an under pitch? The "little" yeast cake that was left inside is most all yeast, not trub, since all my wort is filtered from the kettle. Even though it appears minimal, it should enough to get started?
 

9Kegs

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I ferment 10 gallon batches in 15.5 gallon torpedo kegs (with floating dip tubes) and harvest the yeast. I brew usually within a few days and always take the slurry out and let it warm up a bit before pitching. I also chill down to as close as I can get to fermentation temperature. I always have substantial activity within a few hours.
 
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odie

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How are you harvesting the slurry with a floating dip tube?
 

9Kegs

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Fill a clean bucket with starsan. Drain the fermenting keg until you see the line getting cloudy and just starting to make the empty sound. Dump the starsan out into another bucket. Swirl the keg and pour into the empty sanitized bucket. Best method is start pour and quickly invert. Pour yeast slurry into sanitized mason jars. Anything stuck to the bottom that does not pour out is discarded. Note: I use a hop spider during the boil and also let it settle and clear before transferring into the fermenter.
 
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odie

odie

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I see...you are not serving from the same keg as I am...your method is not applicable to my case.

Nothing wrong with your methods...just not usable for my situation
 

9Kegs

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I am currently fermenting a batch in a 5 gallon keg that I plan to spund and serve from the same keg. I will take note and respond if I do another batch pitching directly upon the yeast cake.
 

theredviper

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Is this possibly an under pitch? The "little" yeast cake that was left inside is most all yeast, not trub, since all my wort is filtered from the kettle. Even though it appears minimal, it should enough to get started?

Thanks I was looking to try the same. Have you ever encountered dead/starved yeast for any reason, like a keg that was around in the fridge for a long time before being finished.

I'm curious about the amount of yeast as well. What are the risks of under pitching? Does fermentation change if the yeast just takes longer to go through everything?
 
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odie

odie

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Thanks I was looking to try the same. Have you ever encountered dead/starved yeast for any reason, like a keg that was around in the fridge for a long time before being finished.

I'm curious about the amount of yeast as well. What are the risks of under pitching? Does fermentation change if the yeast just takes longer to go through everything?
there are always dead yeast. and lots of live yeast. I've heard dead yeast ends up being nutrients for live yeast. Perhaps someone with in depth yeast knowledge can comment?

All the yeast in your fermenter are eventually "starved". Once they run out of sugar to consume, they go dormant. Pitching fresh wort or other sugar source on them they will wake up and go back to doing what they do so well.

I am skeptical about all the "under pitching" drama...so long as you have a single live yeast cell, it will eat sugar and reproduce.

The issue IMO is that a very small starter colony will take time to grow. During that time, other wild yeasts and/or bacteria can also get started. What you want is the desirable yeast to rapidly finish all the sugars before the wild yeast and bacteria can really get started. I'm inclined to think that ALL beers get exposed to wild yeasts and bacteria during fermentation. You just want the good yeast to get the 99.99% share.
 

McMullan

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I'd worry more about the crud left behind by the former residents. That desiccated yeast excrement tastes a lot like yeast excrement. A good landlord would clear up after messy tenants left the building. Also, given enough time, even a beer made with the best intension is likely going to leave unwanted things growing in a keg. It's just more likely to end badly. I don't think it's worth a punt after all the effort of brew day then the time invested in waiting.
 

theredviper

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All the yeast in your fermenter are eventually "starved". Once they run out of sugar to consume, they go dormant. Pitching fresh wort or other sugar source on them they will wake up and go back to doing what they do so well.

I am skeptical about all the "under pitching" drama...so long as you have a single live yeast cell, it will eat sugar and reproduce.

This makes sense. How many times have you re-pitched wort onto the same yeast?

I've read it's better to go from lighter to darker beer styles if you're doing this. I'll give it a shot next time I have the opportunity. I need more kegs(!)
 
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My $0.02, I only repitch on an existing yeast cake if the 2nd beer is a bruiser and the same style. Last month I made a Dry Irish Stout and then put an Imperial Stout straight onto the yeast cake.

I always end up with all sorts of crud on the walls of my stainless fermenter, and the one time tried to just repitch a low-ABV beer onto an existing cake I ended up with mold growing on the krausen line. The batch was a dumper.
 
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odie

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This makes sense. How many times have you re-pitched wort onto the same yeast?

I've read it's better to go from lighter to darker beer styles if you're doing this. I'll give it a shot next time I have the opportunity. I need more kegs(!)
I've only done it twice in a row so far. I racked a fermenter and dumped fresh wort on the yeast cake. Then repeated again with the same fermenter. Both times was a similar type beer.

I think you can go from light to heavy without issues. But only heavy to medium or medium to light....in gravity, color and flavor profile...IMO

Now with fermenting and serving in the keg...I think you would be safe re-pitching several times since everything is sealed up and stays clean. As long as the first batch came out good. The only exposure is when the keg is opened to pitch. Maybe a few minutes at most.
 

beerisyummy

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I've pitched into a dirty fermenter a couple times without ill effects so far as I could tell. In Brewing Better Beer Gordon Strong suggests dumping the slurry into a big mason jar, adding distilled water, shake & let settle. He says you should get three layers of stuff and the yeast is in the middle, so decant the top layer, use the middle and dump the bottom. Haven't tried it myself yet but plan to.
 
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odie

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In Brewing Better Beer Gordon Strong suggests dumping the slurry into a big mason jar, adding distilled water, shake & let settle. He says you should get three layers of stuff and the yeast is in the middle, so decant the top layer, use the middle and dump the bottom.
That is what I understand to be "yeast washing"...the trub settles out first. Decant the rest and let it sit. The yeast will then drop to the bottom and decant the top layer of water.

Now what I've been doing is filtering all the kettle wort before the fermenter so there is no trub to "wash out" later. I just keep all the fermenter slurry which is mostly yeast and beer since trub was separated out before fermentation.
 

beerisyummy

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That is what I understand to be "yeast washing"...the trub settles out first. Decant the rest and let it sit. The yeast will then drop to the bottom and decant the top layer of water.

Now what I've been doing is filtering all the kettle wort before the fermenter so there is no trub to "wash out" later. I just keep all the fermenter slurry which is mostly yeast and beer since trub was separated out before fermentation.

I think you're right, that is indeed "yeast washing." But do tell, are you filtering with an actual filter? Or what?
 
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odie

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I think you're right, that is indeed "yeast washing." But do tell, are you filtering with an actual filter? Or what?
200 micron bucket strainer. I get exceptionally clean wort into the fermenter/keg. I get 100% of the wort into the fermenter/keg. I get exceptionally clean yeast cake to harvest.

I have to reduce my grain bill around 10% to hit target gravity.
 

beerisyummy

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200 micron bucket strainer. I get exceptionally clean wort into the fermenter/keg. I get 100% of the wort into the fermenter/keg. I get exceptionally clean yeast cake to harvest.

I have to reduce my grain bill around 10% to hit target gravity.

Something like this?
 
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odie

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no...they are plastic inserts with a mesh bottom that sit in a standard 5 gal type bucket. Available in many micro ratings...I don't know for sure what mine is, I've long fogot...but I think 200.
 
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