Pressurized Closed Loop Corny Keg Fermenting

[stonebrewer]

@schematix : I hear ya and I understand how others are doing this. To be frank, I am busy/lazy and want to find a few shortcuts to cold side LODO without giving up the benefits. I don't want to water purge the keg if I can let the yeast just eat the O2 up. I don't want to monitor the fermentation. I want to brew great beer and drink it with as little effort as possible, without skipping necessary steps. Seems to me you are onto something with your approach above...i.e. it is a pretty sure bet that your method will eliminate O2 contamination. I want to do the same, but eliminate some of the effort, if possible. Seems to me that if you skipped 1-4 and just move the beer to the SK over while still fermenting (either a little or all of it), it would take care of O2 issue we are all trying to avoid. Am I missing something or is your method being super cautious and conservative? Bottom line is I am going to try both methods and see if I detect any differences...should be a fun experiment! Cheers!

 

[schematix]

I wish all of this were easier. However, I have no reason to believe that this is super cautious, or conservative - it's just the way it is. Feel free to try cutting some corners though and see how you do. It does get easier and quicker the more you do it.

I think the issue with having a headspace full of O2 is that the yeast can't eat it unless it's in solution. So some will diffuse into the beer and the yeast will consume it while the yeast is active, but some will also stay in the headspace and eventually the yeast will go dormat before all has been consumed. And then oxidation sets in.

All i can say is that the more stringent my process, the better the beer got. But that's not to say there's not another way to skin this cat though that's easier.

 

[cheesebach]

I can understand the need for the full water purge of the serving keg if you’re going for the full LoDO process, and you’re trying to preserve the so called delicate malt flavors that are hypersensitive to oxygen. However, I don’t see any reason that adapting the method of purging the serving keg using the CO2 produced by fermentation couldn’t be utilized on its own to provide a better/easier/cheaper method of getting beer transferred to a CO2 purged keg on it own. Compared to the standard homebrewer practice of racking beer through a siphon to the bottom of a regular purged (or not purged) keg and then purging the headspace after transfer, following this process without water purging the serving keg would probably still be an order or magnitude better in terms of O2 exposure. Plus, you’d be saving on CO2 if that matters to you. The volume of CO2 produced by fermentation is probably around 30X the volume of a keg, and you’re bringing in the heavier CO2 from the bottom and pushing the lighter O2 out the top the entire time, which should result in very low O2 by the end.

No, it’s not as good and probably not LoDO-compliant, but if skipping the purge makes it easier for someone to manage on a regular basis, it should still be a major improvement over the most common methods homebrewers have been using for decades.

Disclaimer: I do the full water purge myself, and if I were going through the effort of following a full LoDO part process, I certainly wouldn’t cut any corners on this last little step.

 

[daveMN]

Has anyone had under attenuation problems fermenting in a corny this way? I'm 2 for 2 on underattenuated ferments. The first was a WY Bock yeast that stopped at 60%, the FFT was about 75%. This one, I didn't have my spund valve put together yet and I think the pressure got too high. The second one was Omega's Vermont Ale strain. The temp dropped on this one and the yeast dropped out. In both cases I couldn't get the ferment going by rousing. I'm starting at the bottom end of the temp range for the yeast and letting it free rise to target temp. I'm making a 2L yeast starter, 4L for the Bock. Aerating with oxygen for 2 minutes. Any similar experiences?

 

[schematix]

What pressure are you using?

 

[daveMN]

The Bock was all over the place, that one got up over 25 psi. The second one I used a blowoff tube for the first couple of days then connected to the keg and spund to about 5 psi. I used about 5 drops of Fermcap, but I don't think that was the problem. I'm going to pitch a 2L starter into an Alt tonight at about 55 degrees and let it rise to 60 and hold it there. Probably use a blow-off for the first couple of days then switch to spund at 5 psi. I'm thinking holding the temp and pressure consistently better than I have in the last two is key.

 

[schematix]

It’s possible. I don’t go over about 3.5 psi.

I also have switched to doing blow off for the first half of fermentation so I don’t get as much of a mess in my keg QDs and tubing.

 

[daveMN]

It’s possible. I don’t go over about 3.5 psi.

I also have switched to doing blow off for the first half of fermentation so I don’t get as much of a mess in my keg QDs and tubing.

I'll give 3.5 psi a try. I used a blow-off last time, but didn't get anything using the Fermcap.

 

[raysmithtx]

It’s possible. I don’t go over about 3.5 psi.

I also have switched to doing blow off for the first half of fermentation so I don’t get as much of a mess in my keg QDs and tubing.

Just curious how you are connecting your blow off to the corny keg.

 

[daveMN]

I put some 3/8" tubing over a mfl gas disconnect that goes to a jar of StarSan. I can take a picture of it tonight if you want.

 

[SanPancho]

Not certain but i think the number where you start to impede yeast growth and performance is around 10psi. 25 is definitely no bueno unless you are at FG or near it.

 

[schematix]

1/2” silicone tube zip tied over the gas post. Post and dip tube need to come out.

Too many small cavities in a keg disconnect for me. Pain to clean compared to this.

 

[crane]

Not certain but i think the number where you start to impede yeast growth and performance is around 10psi. 25 is definitely no bueno unless you are at FG or near it.

I regularly go over 10psi. Often times I will start between 5 and 10 psi in the first 12 hrs and hold it there for 3-4 days before raising it to 25psi for the remainder of the ferment.

 

[stonebrewer]

There are many posts out there by pro brewers who state they ferment at pressure in the ranges of 7-24 PSI and claim they have seen no issues with fermentation nor yeast health, as they repitch the yeast and it functions as normal. I personally start out at 10-15PSI and let it get up as high as 25PSI at the end to naturally carbonate. This also has an advantage of keeping the krausen compact, which makes the keg easier to clean. I have had no issues with fermentation, flocculation, or the like. I think the natural carbonation process is far superior to forced carbonation, as I don't get that "carbonic bite" in my naturally carbonated beers that I would get from forced carbonation. YMMV, but this has been my experience. Cheers!

 

[SanPancho]

I regularly go over 10psi. Often times I will start between 5 and 10 psi in the first 12 hrs and hold it there for 3-4 days before raising it to 25psi for the remainder of the ferment.

exactly. by day 4 or 5 the growth phase is long over and you're probably even finishing up with primary. if you've stayed under 10psi then you wouldnt see these problems.

finishing up over 10psi is totally different than starting it there.

 

[schematix]

Some perspective here too...

Every 30” of beer in a tank exerts 1 psi. (I know this isn’t exact, but close enough)

Applying 20 psi is like having a 50’ tank.

 

[stonebrewer]

Some perspective here too...

Every 30” of beer in a tank exerts 1 psi. (I know this isn’t exact, but close enough)

Applying 20 psi is like having a 50’ tank.

That is pressure from weight. Pro brewers also add pressure from natural CO2, so they can carbonate. Again, many pro brewers on other forums claim to ferment under a decent amount of pressure (20 PSI+), without issue. My personal experience has been similar. <shrug>

 

[schematix]

Pressure is pressure regardless of source. My point is that you are in effect simulating an enormous tank, larger than is normally used, by using that much pressure. The shape of primary tanks are much different than those used as secondary/brite tanks.

I experienced sluggishness as well at higher pressures... that's one reason why i went to blow off tube until closer to the end of primary. I don't think pressure is necessarily a good thing when strictly considering yeast.

I'm doing primary for ales in about 2-3 days and lagers in 7-8.

 

[daveMN]

Here's the setup I have right now. I connect to the SK outside the ferm chamber. With the Fermcap, I haven't had krausen come out of the gas post yet, but that could change with this batch. TBD.
I pitched WY1007 last night at 56F with 2 mins of O2, 5 drops of Fermcap, and a pinch of yeast nutrient out of an overabundance of caution. Then I purged the headspace and added the blow-off in the picture. I'll let the temp free rise to 60F. Should I attach the SK and spund when the ferment starts to slow, or wait a little longer?
Hopefully it's ready to ship for a comp on 1/26. Cheers!

 

[schematix]

With the Fermcap, I haven't had krausen come out of the gas post yet, but that could change with this batch. TBD.

Then you're not filling the FV full enough

Should I attach the SK and spund when the ferment starts to slow, or wait a little longer?
Hopefully it's ready to ship for a comp on 1/26. Cheers!

I usually wait until about 50% AA, or until i'm confident the kraussen isn't going to come through. At that point i'm not spunding for carbonation though. I'm spunding to seal the system and give me enough pressure to push samples out so i know exactly when to rack.

 

[stonebrewer]

Pressure is pressure regardless of source. My point is that you are in effect simulating an enormous tank, larger than is normally used, by using that much pressure. The shape of primary tanks are much different than those used as secondary/brite tanks.

I experienced sluggishness as well at higher pressures... that's one reason why i went to blow off tube until closer to the end of primary. I don't think pressure is necessarily a good thing when strictly considering yeast.

I'm doing primary for ales in about 2-3 days and lagers in 7-8.

Not really. Pressure from weight is something you cannot change easily. Beer is going to weigh what it does. Professional brewers distinguish between the two, because they can control the pressure applied by CO2. Your experience and mine do not exactly mesh. That is okay! I don't see an issue with fermenting under pressures of 10-15 PSI during "primary" nor do I see an issue with bumping the pressure to 20+ to carbonate. I go grain to glass in 6-8 days. Shrug.

 

[daveMN]

Not really. Pressure from weight is something you cannot change easily. Beer is going to weigh what it does. Professional brewers distinguish between the two, because they can control the pressure applied by CO2. Your experience and mine do not exactly mesh. That is okay! I don't see an issue with fermenting under pressures of 10-15 PSI during "primary" nor do I see an issue with bumping the pressure to 20+ to carbonate. I go grain to glass in 6-8 days. Shrug.

Are you fermenting in a corny or a different kind of FV?

 

[schematix]

Not really. Pressure from weight is something you cannot change easily. Beer is going to weigh what it does. Professional brewers distinguish between the two, because they can control the pressure applied by CO2. Your experience and mine do not exactly mesh. That is okay! I don't see an issue with fermenting under pressures of 10-15 PSI during "primary" nor do I see an issue with bumping the pressure to 20+ to carbonate. I go grain to glass in 6-8 days. Shrug.

I am referring to the pressure that the yeast sees. That doesn't change. Carbonation is another story. You need what you need to get the desired volumes for the temperature you're at.

For ales i'll be up to around 30 psi during carbonation. Ice cold lager fermentation pressures are like 6-7 psi.

 

[stonebrewer]

Are you fermenting in a corny or a different kind of FV?

Corny with a spunding valve. They are rated for 150 PSI and the PRV releases at 90 PSI. The spunding valve I have can go up to 50 PSI. I have a Zymatic, so most of my fermentation is done this way. I also have a larger system which I brew less often on, and at much larger volume, so I usually do not ferment in the corny with those brews.

 

[SanPancho]

Some perspective here too...

Every 30” of beer in a tank exerts 1 psi. (I know this isn’t exact, but close enough)

Applying 20 psi is like having a 50’ tank.

28 inches to be exact. which i'd have to think is pretty rare in a homebrew setup.

there are certain strains that arent bothered at all by high pressure. and some that just shut down.

That is pressure from weight. Pro brewers also add pressure from natural CO2, so they can carbonate. Again, many pro brewers on other forums claim to ferment under a decent amount of pressure (20 PSI+), without issue. My personal experience has been similar. <shrug>

I think you’re missing some details on your facts and references. Starting at high pressure is entirely different than letting it get there over time. Ask those brewers if they pitch AND pressurize at same time. My guess is no. Capping the tank and letting it run would still likely keep you under 10-15 psi until the second half of the ferment.

As pressure mainly affects growth you could sort of avoid the issue with a big ass pitch. There are also strains which are fine under pressure, or can be moved that way over a few generations. High pressure lager is the example that comes to mind. Im sure there are others.

Lastly, you are wrong about pressure in a conical. And so is schematix. Head pressure is only a measure of the gas pressure in head space and the beer at the very top of the tank. Hydrostatic pressure builds with depth, so pressure in a 280 inch tall tank will be 5psi in headspace but 15 at the cone. In a tall enough vessel you see a gradient of pressure, not a uniform amount. The convection of the wort averages out the pressure that each yeast cell sees over time as it travels in the currents.

Are you adding 10-15-20psi at the same time you pitch your yeast?

 

[stonebrewer]

I don't add CO2, the yeast does by creating CO2 which comes out of suspension into the head space. I don't think I am "wrong" about pressure, I think you and I are saying the same thing, but you are interpreting my writing different than I intended and therefore I did not go into enough detail to clearly state what I was trying to convey. I never said I add CO2 (I don't like the carbonic bite I detect from forced carb) and I never said I started fermentation by pressuring the tank, nor did I say pros do that either.

If I close my spunding valve, I get to 10 PSI quickly...within 24 hours or so. If I don't open it up it day two, it will quickly get over 25 PSI. Early fermentation creates an enormous amount of CO2 (and alcohol, w00t!). So the yeast create all the pressure from CO2, I do not add anything nor do I think any pro brewer adds CO2 from a tank. Hope that clears that up...

During all of fermentation, the yeast is under pressure from CO2 in my setup. This pressure starts at close to 0PSI, ramps to 10-15PSI overnight based on a spring, a weight, a screw, and my discretion. It stays that way for a few days, at which point I close the valve again and let it pressure up to ~25 PSI for carbonating the beer. Push this into a SV that has O2 removed to the best of my ability and into the cold for serving.

I mainly do ales using this methodology. For lagers, I generally do larger batches and use completely different equipment. I love the results and have had zero issues with the beer or the yeast. Again, YMMV...

 

[schematix]

28 inches to be exact.

You are absolutely correct that the static pressure is a function of a depth. I was referring to the pressure at the bottom of the tank. Trying to keep things simple never really works....

But you are not correct on the conversion from psi to inches of water column. Pressure from water is 1 psi per 27.70" of water. Also, wort is not water, so this changes based on the density, which also changes during fermentation. So a typical 1.050 wort only needs 26.38" to create 1 psi (at the bottom).

 

[SanPancho]

You are absolutely correct that the static pressure is a function of a depth. I was referring to the pressure at the bottom of the tank. Trying to keep things simple never really works....

But you are not correct on the conversion from psi to inches of water column. Pressure from water is 1 psi per 27.70" of water. Also, wort is not water, so this changes based on the density, which also changes during fermentation. So a typical 1.050 wort only needs 26.38" to create 1 psi (at the bottom).

in america 1/4psi is equal to a 7" water column. which implies 28" wc for 1psi. you can find that on pretty much any gas appliance. its a standard. easy to remember. a pint is a pound, the world around. etc. ANSI standard? accurate to the nth decimal? no, but good enough.

if we were in a laboratory then fine, show us your decimals.

now if you want to calculate homebrewers on this site being able to accurately measure the difference in pressure between a calculated 28" wc and your actual 27.7" wc in their 5 gallon carboys, you can go ahead and use two decimals. my guess is you'd need them. otherwise, you're just being that guy.

but yes, if you want the win and the last word, ANSI is 27.7 inches. you are the correct guy.

 

[schematix]

but yes, if you want the win and the last word, ANSI is 27.7 inches. you are the correct guy.

Well to be fair you were calling me out for not being completely accurate and simplifying the situation, but then you stated an 'exact' value for something which i had already noted was approximate. And your 'exact' value is also an approximation.

 

[SanPancho]

I don't add CO2, the yeast does by creating CO2 which comes out of suspension into the head space. I don't think I am "wrong" about pressure, I think you and I are saying the same thing, but you are interpreting my writing different than I intended and therefore I did not go into enough detail to clearly state what I was trying to convey. I never said I add CO2 (I don't like the carbonic bite I detect from forced carb) and I never said I started fermentation by pressuring the tank, nor did I say pros do that either.

If I close my spunding valve, I get to 10 PSI quickly...within 24 hours or so. If I don't open it up it day two, it will quickly get over 25 PSI. Early fermentation creates an enormous amount of CO2 (and alcohol, w00t!). So the yeast create all the pressure from CO2, I do not add anything nor do I think any pro brewer adds CO2 from a tank. Hope that clears that up...

During all of fermentation, the yeast is under pressure from CO2 in my setup. This pressure starts at close to 0PSI, ramps to 10-15PSI overnight based on a spring, a weight, a screw, and my discretion. It stays that way for a few days, at which point I close the valve again and let it pressure up to ~25 PSI for carbonating the beer. Push this into a SV that has O2 removed to the best of my ability and into the cold for serving.

I mainly do ales using this methodology. For lagers, I generally do larger batches and use completely different equipment. I love the results and have had zero issues with the beer or the yeast. Again, YMMV...

come to think of it, i stand corrected. its been a while but if i recall, 1plato spits out like 2 or 2.5 volumes. so with a healthy ferm you could easily get to 10 in a day or so, with standard 20% headspace.

the point i keep circling back to is that pressure inhibits growth. which is why i'd guess you're not putting head pressure on, but letting it start at atmosphere. as i also noted before, you can do a huge pitch to mitigate the effects of pressure, but most just let the yeast create the pressure.

as for "lots of pros" doing these high temp ferms, i cant say i believe it. through some luck of knowing some really old school brewers (30+ years in the biz) i've met alot of folks at places like russian river, lagunitas, sierra, stone, ballast, etc. alot of shooting the **** happens, but the few times i've heard of pressurized ferms its been under 10 until they crank it up to spund. which generally is the last plato or two. (i dont know why but the old dudes always use plato- makes my head hurt trying to convert while listening)

lastly, the thing that frustrates me the most about brewing in general, is that there are strains they act totally different from others in certain regards. for every strain that runs like a champ under 20psi, theres another that has to be coaxed along. (this is per the old guys' war stories, not my personal experience). or pulls hop oils out vs others than leave no trace. or need more/less o2. etc.

so yes, in terms of yeast strains, this is very much a YMMV situation. but the one common theme is that you always let the yeast start under atmosphere or very low pressure ( say 1psi to keep o2 out).

i wish i had your luck. my preferred lager strain does NOT like to be under pressure.