Pressurized Yeast Slurry......

[haeffnkr]

Hi,
I am providing the post as a data point, not a suggested how to:

I have been making beer in the same pressurized fermenter ( custom sanke keg ) for a few years. I have made 3 previous batches of beer, in this fermenter/slurry, the last batch was in April, all the beers were similar light lagers, 11 to 13 gallons of wort. I have not cleaned this fermenter in 9 months, nor dumped out the yeast slurry, Omega 114. The last time I made beer I left the fermenter pressurized at co2 serving level and left 4 gallons of beer on the yeast. April.

On Wednesday I pulled off the remaining 4 gallons off and it tasted great, like I am proud of this beer great.

On Friday I depressurized and dumped 11 gallons of 1.043 wort on the slurry in the fermenter and added oxygen. Again, the last time I used slurry was in April. Since April the yeast slurry was in a sealed fermenter under pressure at 34 degrees. ( My free time takes a hit over the spring/summer and brewing takes a back seat )

It was bubbling 3 hours later, 16 hours later it was rolling and I put it under 5 psi and today, Monday morning, less than 3 days it was at 1.012, in 72 hours it was 1.010 and the samples taste great.

I am guessing there was about 1.5 gallons of slurry in the keg based on past experiences. Probably more now....

take care... haeffnkr

 

[odie]

I've got kegs on the 5th or 6th generation of slurry.

been good so far but probably a good idea to eventually harvest the yeast, fully clean the keg and then re-pitch yeast.

 

[day_trippr]

If you're going to put the "harvested" yeast right back in doesn't that imply the keg is essentially "clean" already?

Cheers!

 

[haeffnkr]

I guess so. Or it implies I am just lazy. Or that there is less risk in getting a yeast funk by not handling the yeast and fermenter as conventional brewing wisdom would suggest.

 

[day_trippr]

fwiw, my post was in response to @odie's post...

Cheers!

 

[haeffnkr]

ohhhhhh .... sorry to be so dense

 

[day_trippr]

lol! No harm no foul

 

[odie]

If you're going to put the "harvested" yeast right back in doesn't that imply the keg is essentially "clean" already?

Cheers!

no. I ferment and serve in the same keg. When the keg goes empty, I just fill it with fresh wort and go.

So the keg is "dirty"...but sealed until the pitch. There is dried up krausen all up in the top when I open it. the sides are pretty much clean though.

The assumption is that the keg always remains pressurized, sealed and cold/cool except for a brief minute when fresh wort is dumped in.

 

[day_trippr]

Might be a distinction without functional difference

Cheers!

 

[ba-brewer]

I have wondered if depressurizing the keg quickly could damage the yeast, do you serial keggers do anything special to relieve pressure before refilling?

 

[odie]

no. why would that damage anything?

the big thing is to try to match the temperatures. I let the keg warm up and try to get the wort down target ferm temps, or at least room temps.

It all goes into the ferm chamber in the 60s anyway.

 

[ba-brewer]

Rapid decompression just seems bad, certainly stirs thing up in a container. If warming too fast can damage yeast it seem like other fast changes might also be bad.

How much does the volume of your yeast grow over time or does stay fairly constant?

I ferment clean wort without trub and go from something like 100mL of compact slurry to maybe 500-600mL of compact slurry once it resettles for a single ferment. Wondering whether that stays constant or builds over time.

 

[Bassman2003]

Thanks for sharing. Storing yeast under CO2 really has benefits. Another example of a positive outcome with a low oxygen approach.

Your method is very convenient and works best if you "brew clean". Meaning, striving for very clear wort going into your fermenter. Brewtan B, Whirlfoc and a 20-30min settling period after chilling is a great way.

 

[IslandLizard]

I am guessing there was about 1.5 gallons of slurry in the keg based on past experiences. Probably more now....

Isn't there a point where "overpitching" (using too much yeast) becomes an issue?
I guess yeast growth (budding new cells) goes down, while old and dead yeast builds up.

From what I understand, cells will keep multiplying (budding new cells, aerobic) until they reach a certain population density per ml, before they slide into the (anaerobic) fermentation phase.

 

[odie]

Rapid decompression just seems bad, certainly stirs thing up in a container. If warming too fast can damage yeast it seem like other fast changes might also be bad.

How much does the volume of your yeast grow over time or does stay fairly constant?

I ferment clean wort without trub and go from something like 100mL of compact slurry to maybe 500-600mL of compact slurry once it resettles for a single ferment. Wondering whether that stays constant or builds over time.

the yeast will grow and multiply every time. I also ferment clean without trub.

What happens is when the keg reaches the end, the last pint will pick up the yeast cake and spit a bunch out. That occurs when the floating dip tube hits the yeast cake...the beer is gone.

So this is the point at which you STOP. no more beer and a big yeast cake is all that's left. Move the keg to cold storage and leave it pressurized.

When it's time, pull it out and shake it up a bit, get that cake nice and fluid. Use a short picnic tap and pop all you can into some mason jars and save that yeast.

Then open the keg and see how much yeast is still inside. enough to pitch fresh wort on? good to go. Not much yeast left? ad some back from the mason jars.

My yeast bank has grown a lot. I now have tons of new yeast packs just sitting getting old cause I don't need it. I end up dumping extra yeast a lot.

 

[Yesfan]

the yeast will grow and multiply every time. I also ferment clean without trub.

What happens is when the keg reaches the end, the last pint will pick up the yeast cake and spit a bunch out. That occurs when the floating dip tube hits the yeast cake...the beer is gone.

So this is the point at which you STOP. no more beer and a big yeast cake is all that's left. Move the keg to cold storage and leave it pressurized.

When it's time, pull it out and shake it up a bit, get that cake nice and fluid. Use a short picnic tap and pop all you can into some mason jars and save that yeast.

Then open the keg and see how much yeast is still inside. enough to pitch fresh wort on? good to go. Not much yeast left? ad some back from the mason jars.

My yeast bank has grown a lot. I now have tons of new yeast packs just sitting getting old cause I don't need it. I end up dumping extra yeast a lot.

Exactly the route I want to try. My last two batches were "meh". I underpitched one batch and fermented too high in a vessel that wouldn't hold pressure (Fermzilla). The biggest takeaway is eliminating the middle man which in this case is a dedicated fermenter. With kegs, once fermentation is done, just move it to the kegerator.



Three other questions for you serial keggers (I'm stealing that btw @ba-brewer ) and those who pressure ferment.

1) Will stressed yeast from a previous batch matter (under pitched, too high ferment temp, etc.) in the next batch? I may have asked this before, so I apologize if I have, but one recent video I watched suggested you shouldn't use pressurized yeast slurry from one batch in a batch that doesn't plan on being pressure fermented or vice-versa.

2) (mainly @odie ) If you let the pressure build up near the end of fermentation to carbonate the beer, what then would be a target pressure? Is it just going by a co2 chart like with normal carbing? I have a current batch at 25 psi after fermentation finished (I started at 15psi).

3) Pressurized fermentations lets you ferment at higher temps, so how high can you go? Would a rule of thumb be no more than 10 degrees over a (mainly lager) strain's recommended temp? Does higher pressure allow for higher temps?

I ask as my basement stays in the mid 60s, but in the summer it hits about 70-72F. That's room temp and not fermentation temp during the most active part if I'm pitching at 70F.

I tend to over think things and then second guess myself too. Right now, I'm thinking a 'rule of thumb' is:

1) At 15 psi, stay within a target of 10 degrees over a yeast's recommend temp (in F) for fermentation.
2) Once fermentation starts slowing down, let spunding pressure rise to 25psi. Maybe let sit for a week(?) at that pressure before transferring to serving kegs. If fermenting in the serving keg, then after a couple of days of cold crashing, vent the keg and attach the gas disconnect.

 

[Bassman2003]

Sounds like a reasonable plan.

 

[odie]

OK...I have low pressure PRVs. the blue purple and red ones.

For ales, I always use a blow off tube on the gas post to start. NO PRESSURE. after a couple-few days I will remove the blowoff tube from the gas post and install the poppet and QD fitting. The PRV is always the red one. around 25-35 PSI. at ale fermenting temps that gets me in the range I wanna be. You can vent it periodically to drop it. I keep a PSI guage on the keg. USE THE CHARTS. match PSI to temperature. ALWAYS err to the low side, you can carb up when it's time to tap it.

Lagers...I start with the blue PRV. NO BLOWOFF. pressurize and seal the keg immediately. Blue PRV are around 10psi. perfect for pressure ferments. I run lagers at ale temps with about 10 psi. after a few days I will swap to the red PRV and left it finish same as the ales above.

the purple PRVs are about 15 psi. I never used them.

 

[Yesfan]

I have a few green PRVs on a couple of kegs from More Beer. Yeah, they're a lot higher rated(65psi?), but they didn't have the lower rated red ones. I mainly use them as indicators for my kegs with the floating dip tubes. I limit my batches to 4 gallons when I use my kegs to ferment (one reason I'd like to step up to the 6G Megamouth Torpedos).